Chapter 5 5 Major and Minor Salivary Glands S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo Contents 5.8.7 5.8.8 5.8.9 5.8.10 Cystadenoma . . . . . . . . . . . . . . . . . . . . . . . . 144 Sebaceous Adenoma . . . . . . . . . . . . . . . . . . . 144 Sebaceous Lymphadenoma . . . . . . . . . . . . . . . . 144 Ductal Papilloma . . . . . . . . . . . . . . . . . . . . . 144 5.1 5.1.1 5.1.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 132 Normal Salivary Glands . . . . . . . . . . . . . . . . . 132 Developmental Disorders . . . . . . . . . . . . . . . . 132 5.2 5.2.1 5.2.2 Obstructive Disorders . . . . . . . . . . . . . . . . . . 132 Mucus Escape Reaction . . . . . . . . . . . . . . . . . . 132 Chronic Sclerosing Sialadenitis of the Submandibular Gland (Küttner Tumour) . . . 133 5.9 5.9.1 5.9.2 5.9.3 5.9.4 188.8.131.52 Cribriform Adenocarcinoma of the Tongue . . . . . . 149 5.9.5 Epithelial-Myoepithelial Carcinoma . . . . . . . . . . 150 5.9.6 Hyalinising Clear Cell Carcinoma . . . . . . . . . . . 151 5.9.7 Basal Cell Adenocarcinoma . . . . . . . . . . . . . . . 151 5.9.8 Myoepithelial Carcinoma (Malignant Myoepithelioma) . . . . . . . . . . . . . . 152 5.9.9 Salivary Duct Carcinoma . . . . . . . . . . . . . . . . 154 5.9.10 Oncocytic Carcinoma . . . . . . . . . . . . . . . . . . 155 5.9.11 Malignancy in Pleomorphic Adenoma Malignant Mixed Tumour . . . . . . . . . . . . . . . . 156 184.108.40.206 Carcinoma (True Malignant Mixed Tumour) Ex Pleomorphic Adenoma . . . . . . . . . . . . . . . . 156 220.127.116.11 Carcinosarcoma Ex Pleomorphic Adenoma . . . . . . 157 18.104.22.168 Metastasising Pleomorphic Adenoma . . . . . . . . . 157 5.9.12 Sebaceous Carcinoma . . . . . . . . . . . . . . . . . . . 158 5.9.13 Lymphoepithelial Carcinoma . . . . . . . . . . . . . . 158 5.9.14 Small Cell Carcinoma . . . . . . . . . . . . . . . . . . . 158 5.9.15 Higher Grade Change in Carcinomas . . . . . . . . . 159 5.9.16 Metastatic Malignancies . . . . . . . . . . . . . . . . . 159 Malignant Epithelial Tumours . . . . . . . . . . . . . 144 Acinic Cell Carcinoma . . . . . . . . . . . . . . . . . . 144 Mucoepidermoid Carcinoma . . . . . . . . . . . . . . 146 Adenoid Cystic Carcinoma . . . . . . . . . . . . . . . 147 Polymorphous Low-Grade Adenocarcinoma . . . . . 148 5.3. 5.3.1 5.3.2 Infections . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Bacteria, Fungi . . . . . . . . . . . . . . . . . . . . . . . 133 Viruses . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 5.4 Miscellaneous Infl ammatory Disorders . . . . . . . . 133 5.5 5.5.1 5.5.2 5.5.3 5.5.4 5.5.5 Miscellaneous Non-Infl ammatory Disorders . . . . . 133 Necrotising Sialometaplasia (Salivary Gland Infarction) . . . . . . . . . . . . . . . 133 Sialadenosis . . . . . . . . . . . . . . . . . . . . . . . . 133 Adenomatoid Hyperplasia of Mucous Salivary Glands . . . . . . . . . . . . . . . . 134 Irradiation Changes . . . . . . . . . . . . . . . . . . . . 134 Tissue Changes Following Fine Needle Aspiration . . . . . . . . . . . 134 5.6 5.6.1 5.6.2 5.6.3 Oncocytic Lesions . . . . . . . . . . . . . . . . . . . . . 134 Focal and Diff use Oncocytosis . . . . . . . . . . . . . 134 Ductal Oncocytosis . . . . . . . . . . . . . . . . . . . . 134 Multifocal Nodular Oncocytic Hyperplasia . . . . . . 135 5.7 5.7.1 5.7.2 5.7.3 5.7.4 22.214.171.124 Benign Lymphoepithelial Cyst . . . . . . . . . . . . . 135 126.96.36.199 Cystic Lymphoid Hyperplasia of AIDS . . . . . . . . . 136 5.7.5 Sclerosing Polycystic Sialadenopathy (Sclerosing Polycystic Adenosis) . . . . . . . . . . . . 136 5.7.6 Other Cysts . . . . . . . . . . . . . . . . . . . . . . . . . 137 Cysts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Salivary Polycystic Dysgenetic Disease . . . . . . . . . 135 Mucoceles . . . . . . . . . . . . . . . . . . . . . . . . . 135 Simple Salivary Duct Cysts . . . . . . . . . . . . . . . 135 Lymphoepithelial Cystic Lesions . . . . . . . . . . . . 135 5.10 Hybrid Carcinoma . . . . . . . . . . . . . . . . . . . . 160 5.11 Endodermal Sinus Tumour . . . . . . . . . . . . . . . 160 5.12 Sialoblastoma . . . . . . . . . . . . . . . . . . . . . . . 160 5.13 5.13.1 Predominantly Myoepithelial Malignancies . . . . . . 161 5.13.2 Predominantly Epithelial Malignancies . . . . . . . . 161 Alterations in Gene Expression and Molecular Derangements in Salivary Gland Carcinoma . . . . . . . . . . . . . . 160 5.8 5.8.1 188.8.131.52 Salivary Gland Anlage Tumour (“Congenital Pleomorphic Adenoma”) . . . . . . . . . 140 5.8.2 Benign Myoepithelioma . . . . . . . . . . . . . . . . . 140 5.8.3 Basal Cell Adenoma . . . . . . . . . . . . . . . . . . . . 141 5.8.4 Warthin’s Tumour . . . . . . . . . . . . . . . . . . . . . 142 5.8.5 Oncocytoma . . . . . . . . . . . . . . . . . . . . . . . . 143 5.8.6 Canalicular Adenoma . . . . . . . . . . . . . . . . . . 143 Benign Tumours . . . . . . . . . . . . . . . . . . . . . . 137 Pleomorphic Adenoma . . . . . . . . . . . . . . . . . . 137 5.14 5.14.1 Non-Autoimmune Lymphoid Infi ltrates . . . . . . . . 162 5.14.2 Benign Autoimmune Lymphoid Infi ltrates . . . . . . 162 5.14.3 Malignant Lymphoma . . . . . . . . . . . . . . . . . . 163 5.15 Other Tumours . . . . . . . . . . . . . . . . . . . . . . 163 5.16 Unclassifi ed Tumours . . . . . . . . . . . . . . . . . . . 163 Benign and Malignant Lymphoid Infi ltrates . . . . . 162 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
132 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo 5.1 Introduction 5.1.1 Normal Salivary Glands The salivary glands include paired major glands (pa- rotid, submandibular and sublingual) and minor glands throughout the upper aerodigestive tract. The cellular component comprises serous and mu- cous acinar and ductal epithelial cells, myoepitheli- al cells and connective tissue components (e.g. fat, fi- brous tissue, nerves and blood vessels). The parotid glands consist of predominantly serous acini, the sub- mandibular glands of mixed, serous and mucous aci- ni, while the sublingual glands contain mainly mucous acini. Minor salivary glands also have mixed serous and mucous acini in varying proportions. Of particular interest are the myoepithelial cells. They are a normal constituent of the major and minor salivary glands, and are believed to have contractile properties that assist in the secretion of saliva. Simi- lar cells are also found in the breast, tracheo-bronchi- al and sweat glands. They are plentiful in the salivary acini and intercalated ducts, but much less so in the larger excretory ducts of the major glands. Microscop- ic examination shows that myoepithelial cells are thin and spindle-shaped and situated between the base- ment membrane and epithelial cells, and ultrastruc- turally they are seen to possess a number of cytoplas- mic processes that extend between and over the acinar and ductal lining cells. They display features of both smooth muscle and epithelium, such as numerous mi- crofilaments with focal densities in the cytoplasmic processes, and desmosomes that attach the myoepi- thelial to the epithelial cells . Similarly, immuno- histochemistry shows that myoepithelial cells stain strongly with alpha smooth muscle actin (?SMA), cal- ponin, smooth muscle myosin heavy chain (SMMHC) , h-caldesmon , S-100 protein  as well as with some cytokeratins (e.g. subtype 14). Maspin, p63 [8, 166] and CD 10 [143, 183] have recently been de- scribed as markers of breast myoepithelial cells, and may have a role in identifying their salivary equiva- lents. Preliminary studies show that p63 may well have practical value . Scattered nests of sebaceous cells can be seen in normal parotid and minor salivary glands . Serial sectioning has shown an average of 20 lymph nodes within each parotid , and they may be af- fected by inflammatory processes and neoplasms, both primary and metastatic. Their presence may hamper histologic evaluation of parotid gland lesions . 5 Fig. 5.1. Extravasation mucocele (mucous escape reaction): mu- cin-fi lled cavity lined with granulation tissue and macrophages 5.1.2 Developmental Disorders Agenesis, aplasia, hypoplasia and atresia of the main ducts are all extremely rare. In contrast, intra-parotid nodal heterotopias are very common , and epithe- lial tumours may arise from them . Extranodal heterotopia is rare, and can be subdivided into high (involvement of the ear, pituitary, mandible, etc.) or low forms (lower neck, thyroid). Accessory parotid glands comprising salivary tis- sue separate from the main gland, adjacent to Stenson’s duct, are found in 20% of people. 5.2 Obstructive Disorders 5.2.1 Mucus Escape Reaction This forms an extravasation mucocele, which is defined as the pooling of mucus in the connective tissue in a cav- ity not lined with epithelium. Most patients are under 30 years of age, and the minor glands are most often af- fected. The incidence by site is lower lip 65%, palate 4%, buccal mucosa 10%, and (in the major glands) parotid 0.6%, submandibular 1.2% and sublingual 1.1%. The pathogenesis is traumatic severance of a duct, leading to mucus pooling. It presents in the lip as a raised, of- ten blue, dome shaped swelling of the mucosa, usually 2–10 mm in diameter, but it is generally larger in the sublingual gland in the floor of the mouth where it is known as a ranula. Microscopy shows a well-defined mucin-filled cavity lacking an epithelial lining, but lined with granulation tissue and macrophages (Fig. 5.1).
133 Chapter 5 Major and Minor Salivary Glands 5.2.2 Chronic Sclerosing (Atrophic) Sialadenitis of the Submandibular Gland ( Küttner Tumour) In most if not all cases, this is secondary to calculi in the excretory ducts of the major salivary glands, particu- larly the submandibular gland. It can occur at any age, though the mean is 44 years. Patients present with pain and/or swelling associated with eating. Histology shows acinar atrophy and a chronic inflammatory infiltrate of variable intensity, but it can be heavy with lymphoid ger- minal centre formation. The end stage of destruction of the lobular architecture and scarring has been described as salivary gland cirrhosis . Fig. 5.2. Necrotising sialometaplasia. Most of the ducts and aci- ni are replaced by mature non-keratinising squamous epithelium. Th e lobular architecture of the gland is preserved 5.3 Infections 5.3.1 Bacteria, Fungi 5.5 Miscellaneous Non-Inflammatory Disorders Tuberculosis may involve the gland itself or intra-pa- rotid lymph nodes, and may present as a salivary mass. Other granulomatous infections such as cat-scratch, fungus, sarcoid, leprosy, syphilis, tularaemia, Bru- cella or toxoplasmosis can also occur in the salivary glands. 5.5.1 Necrotising Sialometaplasia (Salivary Gland Infarction) Necrotising sialometaplasia (salivary gland infarction), is a benign, self-healing lesion, affecting especially the minor glands of the palate. Some cases follow surgery (about 1–8 weeks postoperatively) or even relatively mi- nor trauma, such as from an ill-fitting denture, but often no predisposing factor is known, although the underly- ing process is generally considered to be ischaemic . Microscopy shows lobular coagulative necrosis of acini (particularly in the early stages), squamous metaplasia of ducts, a chronic inflammatory cell infiltrate and pseu- doepitheliomatous hyperplasia of the overlying surface . There is a superficial resemblance to either muco- epidermoid or squamous cell carcinoma, but the overall lobular architecture of the involved gland is preserved. A similar reaction can be seen in the major glands after surgery or radiotherapy (Fig. 5.2) . 5.3.2 Viruses Several viral diseases lead to infiltration by chronic in- flammatory cells, but are rarely biopsied. This is espe- cially true of mumps, and also in Cytomegalovirus in- fection, which may involve the salivary glands as part of a systemic infection in either the newborn or immuno- compromised adults, particularly those with AIDS. The diagnosis is made by finding the characteristic enlarged cells with intranuclear inclusions . Other viral in- fections include Epstein-Barr Virus (EBV), Coxsackie virus and influenza virus, as well as human immuno- deficiency virus (HIV). Several lesions may be seen in the salivary glands in patients with AIDS, in particular cystic lymphoid hyperplasia (see Sect. 184.108.40.206). 5.5.2 Sialadenosis 5.4 Miscellaneous Inflammatory Disorders Sialadenosis  is a non-inflammatory process of the salivary glands due to metabolic and secretory disorders of the gland parenchyma accompanied by recurrent painless bilateral swelling of the parotid glands. The peak ages are the fifth and sixth decades . It has been related to endocrine disorders (dia- betes mellitis, ovarian and thyroid insufficiencies) as well as autonomic nervous system dysfunction; the There are a variety of non-infectious inflammatory conditions such as sarcoidosis , Rosai-Dorfman disease , xanthogranulomatous sialadenitis, amyloi- dosis  and Kimura’s disease . They will not be discussed here.
134 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo underlying process appears to be a disorder of sali- vary gland innervation. It is also seen in malnutrition, chronic alcoholism, bulimia, liver cirrhosis and has been linked to some drugs, such as antihypertensive agents . It is rarely biopsied, but histologically there is en- largement of the serous acinar cells (two or three times the normal size) and slight compression of the duct sys- tem by the swollen acini. 5 5.5.3 Adenomatoid Hyperplasia of Mucous Salivary Glands This nodular hyperplastic lesion is usually asymptom- atic, often being noted on routine dental examination. Most cases occur on the palate, but sometimes other mi- nor glands can be involved . It can affect all ages, although most patients are between 30 and 60 years old. There is a slight male predominance. Examination reveals nodular mucosal swellings up to 30 mm in di- ameter. The aetiology is unknown, but possible relevant factors include local trauma due to dentures or tobacco smoking. The main histological feature of adenoma- toid hyperplasia is the presence of hypertrophic and hyperplastic mucous lobules of minor salivary glands. Inflammation, fibrosis and cytological abnormality are not usually seen. Fig. 5.3. Focal oncocytosis of the parotid gland. Some ducts and acinar cells show cytoplasmic oncocytic features farction may be total and squamous metaplasia florid . Possible causes include trauma by the needle  and an increased sensitivity of oncocytic cells to hy- poxia . 5.6 Oncocytic Lesions Oncocytic change is where cells develop intensely eosin- ophilic granular cytoplasm due, to increased numbers of mitochondria . 5.5.4 Irradiation Changes 5.6.1 Focal Salivary glands are very sensitive to radiation, and xe- rostomia is a common complication. Acute radiation injury of salivary glands manifests with swelling, vacu- olation and necrosis of acinar cells. Initial acute inflam- matory response is later followed by chronic sclerosing sialadenitis characterised by loss of acini, focal squa- mous metaplasia, and fibrosis. When all the salivary glands are involved, the loss of saliva is progressive and irreversible. and Diffuse Oncocytosis Foci of oncocytic metaplasia, usually of ducts, but oc- casionally also acini, occur with increasing frequency with advancing age (Fig. 5.3). In contrast, diffuse on- cocytosis of the parotid is extremely rare. Microscopic examination shows oncocytic metaplasia of ducts and acini involving virtually the whole gland. As with most other oncocytic lesions, diffuse oncocytosis comprises two types of cells, light and dark. The former are large and round or polygonal and have finely granular, pink cytoplasm and a single vesicular nucleus. The dark cells are usually more sparse and have deeply eosino- philic, compressed cytoplasm and densely hyperchro- matic nuclei. 5.5.5 Tissue Changes Following Fine Needle Aspiration Fine needle aspiration (FNA) is an important technique in the investigation of salivary disease, particularly tu- mours, but the procedure itself can have adverse effects, causing difficulties in histological assessment and even simulating malignancy. The effects are classified as tis- sue injury with repair, infarction and reactive pseudo- malignant changes . Some or all of these can occur in any tumour  including pleomorphic adenoma, but are most frequent in Warthin’s tumour, where in- 5.6.2 Ductal Oncocytosis Oncocytic metaplasia of ducts often with cystic dilation (also known as oncocytic papillary cystadenoma) occurs mainly in the minor glands, particularly the larynx, and
135 Chapter 5 Major and Minor Salivary Glands only occasionally in the parotid (see Sect. 5.8.10). The lesions are often multifocal and usually small, but can reach 30 mm in diameter. lobular architecture, and some lobules are affected more severely than others. The cysts vary in size up to a few millimetres, and they are irregular in shape and often interconnect. The lining epithelium is flat, cu- boidal to low columnar, sometimes with an apocrine- like appearance. The lumen contains secretion with spherical microliths. Remnants of salivary acini are seen between the cysts, and thick fibrous interlobular septa are often prominent. 5.6.3 Multifocal Nodular Oncocytic Hyperplasia This rare condition consists of nodules of varying size, composed of oncocytic cells, often with relatively clear cytoplasm. The nodules appear to engulf normal acini giving a false impression of invasion, but there is no stromal or other response by the acini. Multifocal nodu- lar oncocytic hyperplasia (MNOH) can be mistaken for a clear cell neoplasm with satellite deposits when one nodule is much larger than the others. MNOH can also be bilateral, and it has been reported to co-exist with a pleomorphic adenoma, which itself showed oncocytic change [20, 158]. 5.7.2 Mucoceles A mucocele is defined as the pooling of mucus in a cys- tic cavity . Two types are recognised – extravasation and retention; extravasation mucocele is described in Sect. 5.2.1. Retention cysts can occur at any age, and the mucus pool is within an epithelium-lined cavity, likely to be a dilated excretory duct. 5.7 Cysts 5.7.3 Simple Salivary Duct Cysts Non-neoplastic cysts and pseudocysts accounted for about 6% of all lesions of the salivary glands in the Ham- burg registry of salivary neoplasms and tumour-like le- sions . They can be classified as: 1. Dysgenetic, e.g. polycystic dysgenetic disease; 2. Acquired cysts lined with epithelium, e.g. lympho- epithelial cystic lesions, duct cysts; 3. Pseudocysts without an epithelial lining, e.g. extrava- sation mucocele, including ranula; 4. Cystic change in neoplasms, e.g. Warthin, variants of mucoepidermoid and acinic cell carcinomas, lym- phoepithelial sialadenitis (LESA), lymphoma, and rarely, pleomorphic adenoma; 5. Miscellaneous other cysts. Salivary duct cysts are acquired, and are due to dilata- tion of a salivary duct following obstruction, sometimes by a tumour . They can occur at any age, although usually in patients over 30 years old. Most (85%) arise in the parotid and are unilateral and painless. They are well-circumscribed, unilocular and up to 100 mm in di- ameter (usually 10 to 30 mm). They contain fluid that is watery to viscous brown, occasionally with mucus. The wall comprises dense fibrous tissue, 1–3 mm thick, and there is often mild to moderate chronic inflammation, although not the dense lymphoid infiltrate of a lympho- epithelial cyst. The epithelium is stratified squamous, or a single layer of cuboidal or columnar cells, with occa- sional goblet cells and oncocytes. The commonest are mucoceles, including ranula (80%), parotid duct cysts (11%), lymphoepithelial cystic lesions (7%) and dysgenetic cysts and congenital sialectasia (to- gether 2%). 5.7.4 Lymphoepithelial Cystic Lesions Seven types of salivary lesions can be characterised by single or multiple epithelial-lined cysts surrounded by lymphoid tissue including germinal centres: benign lymphoepithelial cyst and cystic lymphoid hyperpla- sia of AIDS, in addition to Warthin’s tumour, LESA and mucosa-associated lymphoid tissue (MALT lym- phoma) each with cystically dilated ducts, low-grade cyst-forming mucoepidermoid carcinoma with a heavy lymphocytic response, and cystic metastases in intra- parotid lymph nodes, each of which is discussed in Sect. 5.14. 5.7.1 Salivary Polycystic Dysgenetic Disease This very rare condition resembles cystic anomalies of other organs, such as the kidney, liver and pancreas, although no association has been described [62, 172, 177]. Some cases are familial , and almost all cases occurred in females. Most patients present in childhood, but some have not been recognised until adulthood. It only affects the parotid glands, usually bilaterally. Microscopically, the glands maintain their
136 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo 5 Fig. 5.4. Simple, benign lymphoepithelial cyst. Th e cavity is lined with columnar and cuboidal cells with scattered goblet cells. Th e surrounding tissue contains small lymphocytes and macrophages. Beyond this is a capsule and subcapsular space resembling that of a lymph node Fig. 5.5. Sclerosing polycystic adenosis. Cystic ducts of varying size with stromal fi brosis, resembling fi brocystic disease and scle- rosis adenosis of the breast. Th ere is also proliferation of ducts and acini in a lobular pattern 220.127.116.11 Benign Lymphoepithelial Cyst atrophic, and multiple cystic spaces are seen, filled with mucoid or gelatinous fluid. The cysts are dilated ducts, and the lining sometimes shows squamous metaplasia. The cysts are infiltrated by lymphoid cells, including variable numbers of marginal zone B-cells, and in time lymphoepithelial lesions are apparent. There is considerable morphological overlap with LESA [60, 91], but only a minority of patients exhibit the clinical features of Sjögren’s syndrome . An im- portant practical point is that this lesion can be the first clinical manifestation of HIV disease, and thus histo- logical identification of it means a diagnosis of AIDS for the patient. The lymphoid infiltrate is polyclonal and generally does not progress to lymphoma, although patients with HIV disease are at risk of developing aggressive B-cell lymphomas, most commonly of the Burkitt-type and diffuse large cell lymphoma . An exception is that in children with AIDS, the infiltrate more closely resem- bles MALT lymphoma, and monoclonality may be dem- onstrated. Benign lymphoepithelial cysts are thought to arise either in intraparotid lymph nodes  or from remnants of the branchial apparatus . There is no clinical association with Sjögren’s syndrome, and they were described long before the AIDS epidemic. There is a slight male prepon- derance (1.6:1 in civilians in the Armed Forces Institute of Pathology [AFIP] series), and the mean age of onset is 46 years (range 18 to 79) . They are usually solitary, but can occasionally be bilateral. The average diameter is 25 mm, but they may reach 70 mm. Microscopy shows the lining epithelium to be squamous, respiratory, cuboidal, columnar or a combination, and small numbers of gob- let cells may also be present (Fig. 5.4). This lining is sur- rounded by abundant lymphoid tissue composed of small lymphocytes, plasma cells and germinal centres; lympho- epithelial lesions are not a feature. Benign lymphoepithe- lial cysts are not known to recur after surgical excision. 18.104.22.168 Cystic Lymphoid Hyperplasia of AIDS 5.7.5 Sclerosing Polycystic Sialadenopathy (Sclerosing Polycystic Adenosis) A nodular or diffuse enlargement of particularly the pa- rotid glands is often seen in HIV-positive patients – usu- ally bilaterally. Microscopic examination shows a dense lymphoid infiltrate including follicular hyperplasia, sometimes displaying lysis of germinal centres and di- minished mantle zones. There is an elaborate dendritic reticulum cell network within which there is evidence of active HIV replication, although the exact histogen- esis of this lesion is not understood. Plasma cells (poly- typic) are often numerous. The glandular parenchyma is This is a benign pseudoneoplastic condition of major salivary glands [11, 84, 200], said to be analogous to fi- brocystic disease of the breast . It affects mainly fe- males with a mean age of 28 years (range 12 to 63). Most cases have been described as slow-growing masses in the parotid gland, with a single example of submandibular gland involvement. The excised gland is largely replaced
137 Chapter 5 Major and Minor Salivary Glands by multiple discrete, firm, rubbery nodules. Microscop- ic examination shows a well-circumscribed, unencapsu- lated mass composed of a lobular arrangement of pro- liferating ducts and acini with cystic ducts containing viscous secretion and, on occasions, aggregates of foamy macrophages. There is often intraluminal epithelial proliferation occasionally with a cribriform pattern and these may contain small droplets of basement membrane material. The lining comprises a spectrum of apocrine, mucous, squamous cells and ballooned sebaceous-like cells, although true goblet cells are not seen. Some cells contain prominent large, intensely eosinophilic cyto- plasmic granules of varying sizes, representing aberrant zymogen granules (Fig. 5.5). On occasion there is nucle- ar pleomorphism, even suggesting dysplasia , but there is no significant mitotic activity and no malignant cases have been described. Flattened myoepithelial cells are present around ductal and acinar structures, and there is periductal sclerosis and intense hyaline sclero- sis of the surrounding soft tissue. Sometimes, a patchy lymphocytic infiltrate is noted. About one-third of cases recur, but none has metastasised. Fig. 5.6. Pleomorphic adenoma spectrum. Reproduced with per- mission from Zarbo et al.  ther sex and at any age. Up to 80% occur in the super- ficial lobe of the parotid gland, and it typically presents as a painless swelling. When the deep lobe is involved, it often manifests as an intraoral parapharyngeal mass. Approximately 5% of PAs occur in the submandibular gland, 0.1% in the sublingual gland and about 10% in minor salivary glands [30, 228]. Similar tumours arise in extrasalivary locations including bronchi, ear, lacri- mal gland, breast and skin. Macroscopically, PAs are usually well-circumscribed masses of 20–40 mm. The cut surface is usually white, and grey glistening areas are commonly seen. Histologically, PA was defined by the revised WHO Classification of 1991 as “a tumour [of the salivary glands] of variable capsulation characterised micro- scopically by architectural rather than cellular pleomor- phism” , i.e. the pleomorphism refers to the variety of histological patterns, not the cytology. The pattern varies from case to case, and also from area to area within any individual tumour. All are com- posed of a mixture of ductal epithelial cells, basal and myoepithelial cells and variable amounts of stroma, both hyaline and chondromyxoid. Attempts have been made to subclassify PA based on the proportions of cell types and stroma , but because of the variation in any tumour, this is difficult and probably has no prog- nostic value. Ducts are lined with flat, cuboidal or columnar epi- thelial cells, with little or no atypia. The ducts are usu- ally small tubules, but can be cystically dilated and also arranged in a cribriform pattern, resembling ade- noid cystic carcinoma, but mitotic figures are rare and the proliferation index low (see Sect. 5.9.3). Squamous metaplasia with or without keratinisation is seen in up to 25% of PAs . If associated with mucinous meta- plasia, it may resemble mucoepidermoid carcinoma (Figs. 5.7, 5.8). Myoepithelial cells are arranged in sheets, small- er islands and trabeculae, and also surround epithe- 5.7.6 Other Cysts Other salivary cysts include dermoids , and a vari- ety of epithelial and non-epithelial cysts including para- sites and gas cysts in glass blowers . Keratocystoma is a rare, recently described, benign parotid tumour characterised by multicystic keratin-filled spaces lined with stratified squamous epithelium with no atypical features . 5.8 Benign Tumours There are various classifications. The revised WHO classification (Table 5.1)  has the merit of being eas- ily applicable in practice . 5.8.1 Pleomorphic Adenoma ICD-O:8940/0 Most authors accept that there is a spectrum of benign salivary adenomas, including pleomorphic adenoma. Benign myoepithelioma, which is composed almost entirely of myoepithelial cells represents one end of the spectrum, whereas basal cell adenoma and canalicular adenoma are at the other end [183, 236, 237]. The partic- ular morphology of any particular tumour reflects the different proportions of the constituent cells (Fig. 5.6). Pleomorphic adenoma (PA) is the most common tu- mour of the salivary glands. Although most often found in young to middle-aged women, they can occur in ei-
138 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo Table 5.1. Revised WHO histological classifi cation of salivary gland tumours  Adenoma Pleomorphic adenoma Myoepithelioma (myoepithelial adenoma) Basal cell adenoma Warthin’s tumour (adenolymphoma) Oncocytoma (oncocytic adenoma) Canalicular adenoma Sebaceous adenoma Inverted ductal papilloma Intraductal papilloma Sialadenoma papilliferum Papillary cystadenoma Mucinous cystadenoma Acinic cell carcinoma Mucoepidermoid carcinoma Adenoid cystic carcinoma Polymorphous low-grade adenocarcinoma (terminal duct adenocarcinoma) Epithelial-myoepithelial carcinoma Basal cell adenocarcinoma Sebaceous carcinoma Papillary cystadenocarcinoma Mucinous adenocarcinoma Oncocytic carcinoma Salivary duct carcinoma Adenocarcinoma (not otherwise specified) Malignant myoepithelioma (myoepithelial carcinoma) Carcinoma in pleomorphic adenoma Squamous cell carcinoma Small cell carcinoma Undifferentiated carcinoma Other carcinomas Ductal papilloma 5 Cystadenoma Carcinomas Non-epithelial tumours Malignant lymphomas Secondary tumours Unclassified tumours Entities not included in the classification, but described or better characterised since 1991 [8a] Sialoblastoma Hyalinising clear cell carcinoma Cribriform adenocarcinoma of the tongue Endodermal sinus tumour of the salivary glands lium-lined spaces. As in benign myoepithelioma (see Sect. 5.8.2), neoplastic myoepithelial cells may take sev- eral forms – epithelioid, spindle, plasmacytoid, clear and oncocytic, as well as transitional forms with features of two or more of these types (Fig. 5.9). The stroma varies in amount and is either dense eo- sinophilic hyaline material or chondromyxoid tissue. The former is composed of basement membrane mate- rial and stains with PAS diastase and collagen type IV; the chondromyxoid material only rarely resembles true cartilage and is Alcian blue-positive (Fig. 5.10). Calcifi- cation and bone formation can occur in long standing tumours. Occasionally, collagenous spherules and crys- talloids are seen, particularly in tumours rich in myo- epithelial cells of the plasmacytoid type (Fig. 5.11) . Nuclear atypia is not common, but can be seen in tu- mours where epithelial or myoepithelial cells display on- cocytic features . Occasional myoepithelial cell nu- clei are enlarged and bizarre, somewhat analogous to “ancient” change in schwannomas. Mitotic figures are generally sparse, but can occur as part of the repair pro- cess after FNA. Such tumours with these atypical fea- tures should be sampled thoroughly to exclude true in- tracapsular carcinoma. Similarly, areas of necrosis or haemorrhage may fol- low surgical manipulation, FNA or other trauma, and
139 Chapter 5 Major and Minor Salivary Glands Fig. 5.7. Pleomorphic adenoma: myoepithelial cells with an epi- thelioid cytomorphology. Th ese cells may also be spindle-shaped, plasmacytoid (hyaline) or have clear cytoplasm. Note also a small duct and a focus of squamous metaplasia. Keratinising squamous metaplasia is seen in up to a quarter of pleomorphic adenomas Fig. 5.10. Pleomorphic adenoma: chondromyxoid stroma con- taining isolated small and small aggregates of myoepithelial cells Fig. 5.8. Pleomorphic adenoma with squamous and focal muci- nous metaplasia resembling mucoepidermoid carcinoma Fig. 5.11. Collagenous spherules can be seen in some benign myo- epitheliomas and myoepithelium-rich pleomorphic adenomas Fig. 5.9. Pleomorphic adenoma: myoepithelial cells showing an epithelioid and plasmocytoid appearance Fig. 5.12. Vascular “invasion” is a rare fi nding in benign pleo- morphic adenoma, due to displacement of neoplastic cells into vascular spaces. It is not indicative of malignancy
140 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo 5 Fig. 5.14. Benign myoepithelioma composed of plasmocytoid (hyaline) and epithelioid cells with areas of myxoid stroma. Plas- mocytoid cells have eccentric nuclei and dense eosinophilic cy- toplasm Fig. 5.13. Recurrent pleomorphic adenoma. Multiple and oft en well-separated tumour nodules of diff erent sizes are seen in the periparotid soft tissue 22.214.171.124 Salivary Gland Anlage Tumour (“ Congenital Pleomorphic Adenoma”) these neoplasms should also be sampled thoroughly. Tu- mour cells in lymphatics (“vascular invasion”) are occa- sionally seen in benign PAs, but this does not necessarily indicate malignancy (Fig. 5.12) . None of the reported cases were followed by metastases. Pleomorphic adenomas are often completely or part- ly surrounded by a fibrous capsule of variable thickness, but it can be absent, especially in tumours of the minor glands. Neoplastic elements may extend into and even through the capsule in the form of microscopic pseudo- podia or apparent satellite nodules. They may be the cause of future recurrence after ap- parent surgical removal , and their presence should be noted in the surgical pathology report. Special stains and immunohistochemistry are not necessary for the diagnosis in most cases, but can be used to identify the different cell types and also early malignant change (see Sect. 5.9.11). Recurrent PA occurs after incomplete surgical exci- sion and is usually composed of multiple nodules com- pletely separate from each other. In the first recurrence the nodules are usually seen within salivary gland tis- sue, but in further recurrences tumours are found in the soft tissue of the surgical bed (Fig. 5.13). Histologically, the nodules show similar features to ordinary PA, and in particular they lack any cytological atypia. In spite of this, confluent nodules of recurrent PA can still kill the patient. As discussed later (see Sect. 5.9.11) multi- ply recurrent PAs may rarely metastasise to distant sites, and in addition are more prone to developing malignant changes. ICD-O:8940/0 This is a rare, probably hamartomatous lesion in the na- sopharynx of neonates . Although potentially fatal due to its location, prognosis after surgery is good. It was not included in the 1991 WHO classification . The microscopic features are a biphasic pattern of squamous nests and duct-like structures at the periphery, merging into solid, predominantly mesenchymal nodules, possi- bly of myoepithelial origin. Occasionally, there is necro- sis and cyst formation . 5.8.2 Benign Myoepithelioma ICD-O:8982/0 Myoepithelial cells are found in several salivary gland neoplasms (Table 5.2). Benign myoepithelioma was first described in 1943 , and was included in the 1991 revised WHO classification . It can be defined as a tumour composed totally, or almost to- tally, of myoepithelial cells. Whether or not it is tru- ly a separate biological entity is debatable, but most commentators believe that it represents one end of a spectrum that also includes pleomorphic and at least some basal cell adenomas. Nevertheless, myoepithe- lioma displays particular microscopic features that pose specific practical problems in the identification and differential diagnosis, and on this basis it can be accepted as a separate diagnostic category [188, 189]. Most cases present as a well-circumscribed mass, usu-
141 Chapter 5 Major and Minor Salivary Glands Table 5.2. Salivary tumours with myoepithelial cell participation. Adapted from the WHO classifi cation  Benign Pleomorphic adenoma Myoepithelioma Basal cell adenoma (some) Malignant Adenoid cystic carcinoma Polymorphous low-grade adenocarcinoma Epithelial-myoepithelial carcinoma Malignant myoepithelioma (myoepithelial carcinoma) Carcinoma ex pleomorphic adenoma (some) ally 10–50 mm in diameter, in either major or minor salivary glands. Microscopically, there are several typ- ical appearances, reflecting the different forms that neoplastic myoepithelial cells can take. Solid, myxoid and reticular growth patterns may be seen, and the component cells may be spindle-shaped, plasmacy- toid (hyaline), clear, epithelioid or oncocytic. Many tumours show more than one growth pattern or cell type, but myoepitheliomas of the minor glands are more often composed of plasmacytoid cells, and those of the parotid spindle cells . Although most au- thors accept the plasmacytoid cells as myoepithelial, it has recently been suggested that these cells originate from luminal and not from myoepithelial cells , and thus the tumours should possibly be reclassified as plasmacytoid adenomas . The clear cell variant can occur in both major and minor glands , but is relatively rare . Unlike their malignant counter- part  (see Sect. 5.9.8), benign myoepitheliomas do not usually show invasiveness, necrosis, cytological pleomorphism, or more than an isolated mitotic fig- ure. The stroma is usually scanty, fibrous or myxoid, and it may occasionally contain chondroid material or mature fat cells . Extracellular collagenous crys- talloids are seen in 10–20% of plasmacytoid cell-type myoepitheliomas, (as well as sometimes in myoepithe- lial-rich PAs); these structures are about 50–100 ?m in diameter and consist of radially-arranged needle- shaped fibres composed of collagen types I and III, which stain red with the van Gieson method . Scanty small ducts may be present (usually less than 10% of the tumour tissue) in otherwise typical myo- epitheliomas (Fig. 5.14) . Immunohistochemical- ly, almost all tumours express S-100 protein, as well as some cytokeratins, especially subtype 14. Alpha smooth muscle actin positivity is seen to some degree in most spindle cell myoepitheliomas, but only oc- casionally in the plasmacytoid cell type . Stain- ing for calponin, smooth muscle myosin heavy chain (SMMHC) and CD10 is inconsistent in myoepithelial cells. The nuclear transcription factor p63 is positive in most benign myoepitheliomas . Electron mi- croscopic studies have also confirmed both epithelial Fig. 5.15. Basal cell adenoma. Th e tumour is arranged in nests, is- lands and trabeculae or basal cells without cytological abnormal- ity. Ductal diff erentiation is also noted and smooth muscle differentiation , although fo- cal densities in myofilaments are not usually found . The behaviour of myoepithelioma is similar to that of pleomorphic adenoma, and complete excision should be curative. Neither growth pattern nor cell type appears to carry prognostic significance. Malig- nant change in a benign lesion has been described , but too little information is available about the per- centage of cases involved. However, it is reasonable to postulate that it is probably not very different from that of pleomorphic adenoma. 5.8.3 Basal Cell Adenoma ICD-O:8147/0 Most tumours previously described as monomorphic adenoma are now termed basal cell adenoma (BCA). The revised WHO  classification recognises four histopathological subtypes – solid, tubular, trabecular and membranous – but it is likely that, in reality, there are only two separate biological entities  – mem- branous and non-membranous (Figs 5.15, 5.16).
142 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo or hair follicle origin, usually cylindromas or eccrine spiradenomas. The most important differential diagnosis of all types of BCA is adenoid cystic carcinoma. Useful pointers to adenoma include lack of invasiveness and cytological pleomorphism, low mitotic and proliferative activity, and whorled eddies of epithelial cells. S-100 protein pos- itivity of spindled stromal cells may help, as this does not occur in adenoid cystic carcinoma . BCA close- ly resembles basal cell adenocarcinoma, which may lack cytological pleomorphism and mitotic figures, the diag- nosis then depending principally on the presence of gen- uine invasion (see Sect. 5.9.7). The recurrence rate for non-membranous BCA is extremely low (0 out of 102 patients in one series) , and local excision with clear margins is sufficient treat- ment. There is a low rate of malignant transformation (about 4%) into basal cell adenocarcinoma . In con- trast, up to 24% of membranous BCAs recur after sur- gery , probably reflecting multicentricity and, in ad- dition, malignancy (also as basal cell adenocarcinoma) develops in 28% . Surgery for this subtype needs to be more extensive [16, 119, 130]. 5 Fig. 5.16. Membranous basal cell adenoma: jigsaw like pattern: multiple epithelial islands surrounded by large amounts of basal membrane-like material. Th e latter is also present within the cyto- plasm of some of the small dark hyperchromatic basal cells. Th ere is little cellular pleomorphism Non-membranous BCAs have an equal sex inci- dence and arise mostly in the major glands. They prob- ably represent part of the spectrum of myoepithelio- ma and pleomorphic adenoma [70, 237]. The tumours are ovoid, well-circumscribed masses in which is- lands, nests and trabeculae of basaloid cells are each surrounded by a distinct thin PAS-positive basement membrane. The component cells may take two forms – small with scanty cytoplasm and a round, dark nucle- us, and larger with amphophilic or eosinophilic cyto- plasm and an ovoid paler staining nucleus. These two types are intermixed, but the smaller cells tend to be arranged around the periphery of the nests and trabec- ulae, giving the appearance of palisading. Ductal dif- ferentiation may or may not be apparent, but can be highlighted by EMA. There is little pleomorphism and mitotic figures are rare. The stroma varies in amount and cellularity, but S-100 protein-positive spindle cells may be numerous. S-100 positive cells are also pres- ent within the islands of epithelial cells, which react strongly with cytokeratins . Membranous BCA (dermal analogue tumour) oc- curs predominantly in men, and can be multicentric. Most arise in the major glands, including within in- traparotid lymph nodes . Microscopically, they are not encapsulated and appear multinodular, of- ten with a jigsaw-like pattern. The most characteristic feature is the deposition of large amounts of hyaline basement membrane material, which is brightly eosin- ophilic and PAS-positive. It surrounds the epithelial cell islands and blood vessels, and is present within the islands as small droplets. There is little pleomor- phism or mitotic activity. In about 40% of cases, the salivary adenoma is associated with synchronous and often multiple skin appendage tumours of sweat gland 5.8.4 Warthin’s Tumour ICD-O:8561/0 Warthin’s tumour (WT; adenolymphoma) is the second commonest neoplasm of the parotid gland, and is the easiest salivary tumour to diagnose by microscopy . It arises almost exclusively in the parotid gland (usually the tail) and occasionally in periparotid lymph nodes. The mean age at diagnosis is 62 years (range 29–88), and WT is uncommon in blacks. Previously, there was a marked male predominance (as much as 26:1), but now there is an almost equal sex distribution. It is eight times more frequent in heavy smokers. WT is multicentric in 12% of patients, and bilateral in 6%. There are two theories of its histogenesis  – a true epithelial neoplasm that attracts a heavy lymphoid re- action, or alternatively a non-neoplastic lesion arising from ectopic salivary inclusions in intraparotid lymph nodes. The latter theory is supported by a molecular ge- netic study using HUMARA analysis, which has shown that WT is not a clonal process . Pathological examination shows a well-circum- scribed oval mass, composed of slits or cystic spac- es with papillary infoldings lined with two layers of oncocytic epithelium; the inner cells are columnar with nuclear palisading, deep to which are flattened or cuboidal basal cells (Fig. 5.17). Occasional mucous and squamous cells may be seen. The stroma com- prises usually plentiful lymphoid tissue with germi- nal centre formation. Special stains and immunohis- tochemistry have little to offer in practice; myoepi-
143 Chapter 5 Major and Minor Salivary Glands Fig. 5.17. Warthin’s tumour. Cystic and slit-like spaces with pap- illary infolding lined with oncocytic cells. Lymphoid tissue occu- pies the cores of most papillae Fig. 5.20. Canalicular adenoma of the upper lip. It is composed of bi-layered strands of basal-like cells embedded in a loose oede- matous stroma thelial markers are negative. Histological variants in- clude a stroma-poor form, and metaplastic WT – in the latter, much of the original oncocytic epithelium has been replaced by squamous cells, and there is ex- tensive necrosis, fibrosis, inflammation, and granu- loma formation (Fig. 5.18) . This not uncommon lesion follows trauma, particularly FNA , and can be mistaken for squamous or mucoepidermoid carci- nomas (see Sect. 5.5.5). WT generally has a good out- come, with recurrence rates of about 2%. Malignancy occurs in less than 1% of cases, involving either epi- thelial or lymphoid elements leading to carcinomas or lymphomas . Fig. 5.18. Metaplastic (infarcted) Warthin’s tumour. Th ere is ex- tensive necrosis. A surrounding thin rim of viable tissue shows squamous metaplasia 5.8.5 Oncocytoma ICD-O:8290/0 Oncocytic change in salivary tumours is common (see Sect. 5.6) . Oncocytoma is a true benign neoplasm composed of oncocytes. It is rare and is often associ- ated with MNOH (see Sect. 5.6) . It comprises a well-demarcated mass of oncocytic cells (both light and dark) with a solid, trabecular, or tubular configuration (Fig. 5.19). There is a surrounding, usually incomplete fibrous capsule, and only a little internal fibrous stroma. There is a rare clear cell variant . 5.8.6 Canalicular Adenoma ICD-O:8149/0 Canalicular adenoma also has a basaloid appearance. Its location is almost exclusively intraoral, particu- larly affecting the upper lip  and less often the palate. As a result, most tumours present when small Fig. 5.19. Oncocytoma. Light and dark oncocytic cells are ar- ranged in a solid, trabecular and tubular confi guration
144 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo – rarely more than 20 mm in diameter. It has a char- acteristic morphology of branching and interconnect- ing bi-layered strands of darkly staining epithelial cells set in a loose vascular stroma (Fig. 5.20). There is no pleomorphism or significant mitotic activity. The cells express cytokeratins and S-100 protein. Not infrequently, they are multifocal , and can thus mimic the true invasiveness of cribriform adenoid cystic carcinoma. The lack of destructiveness and the presence of blood vessels in the cribriform spaces are good guides to canalicular adenoma, which is com- pletely benign. Occasional recurrences are a result of multifocality . 5 Fig. 5.21. Oncocytic (papillary) cystadenoma of the larynx. Cys- tically dilated ducts are lined with oncocytic cells 5.8.7 Sebaceous Adenoma ICD-O:8410/0 This rare, encapsulated epithelial tumour is composed of solid, variably shaped islands and cysts, both showing focal sebaceous differentiation with squamous areas; these are surrounded by a fibrous, hyalinised stroma. They do not recur after complete surgical excision [12, 62]. nous cystadenoma. Both are rare, benign tumours characterised by unicystic or multicystic growth pat- terns. The latter can be mistaken for mucinous ma- lignancy, such as grade I mucoepidermoid carcinoma [62, 173]. Most cystadenomas are multilocular with individual cystic spaces separated by limited amounts of intervening stroma . The lumina often contain eosinophilic material with scattered epithelial, foamy or inflammatory cells. Rarely, psammoma bodies and crystalloids have been described within the luminal secretion . The lining epithelium of the cystic spaces is mostly columnar and cuboidal. Oncocytic, mucous and apocrine cells are sometimes present fo- cally or may predominate. An oncocytic variant of papillary cystadenoma is composed of oncocytes pres- ent in unilayered or bilayered papillary structures (Fig. 5.21). Squamous epithelium may be present, but rarely predominates. The tumours are unlikely to re- cur, but rare cases of mucinous cystadenoma with ma- lignant transformation have been described (Figs 5.22, 5.23) . 5.8.8 Sebaceous Lymphadenoma ICD-O:8410/0 This lesion comprises irregular proliferating nests and islands of epithelium including solid and gland-like se- baceous elements, surrounded by a lymphoid stroma. It is possible that, like Warthin’s tumour, sebaceous lymphadenoma develops from salivary inclusions with- in lymph nodes, and shows sebaceous rather than onco- cytic metaplasia [62, 171]. 5.8.9 Ductal Papilloma ICD-O:8503/0 There are three subtypes, all rare – inverted ductal pap- illoma (similar to the sinonasal tumour), intraductal papilloma and sialadenoma papilliferum (similar to skin syringocystadenoma papilliferum) . Intraduct- al papilloma has a fibrovascular core lined with myoepi- thelial and ductal cells and it is usually seen in a dilated duct. 5.9 Malignant Epithelial Tumours 5.9.1 Acinic Cell Carcinoma ICD-O:8550/3 Acinic cell carcinoma (AcCC) is defined as a malignant epithelial neoplasm in which some of the neoplastic cells demonstrate serous acinar cell differentiation. It accounts for about 2–4% of salivary gland tu- mours, and 12–17% of malignancies . It is slight- ly commoner in women and the mean age at presen- tation is 44 years, although AcCCs can affect children 5.8.10 Cystadenoma ICD-O:8440/0 The revised WHO classification recognises two histo- pathological subtypes –papillary cystadenoma (simi- lar to lymphoid-poor Warthin’s tumour) and muci-
145 Chapter 5 Major and Minor Salivary Glands Fig. 5.22. Mucinous cystadenoma. Cysts are lined with mucus- secreting cells without atypia Fig. 5.24. Acinic cell carcinoma solid variant. Th e cells show granular cytoplasm and acinar diff erentiation similar to normal salivary gland acini Fig. 5.23. Mucinous cystadenoma with malignant transformation . Cellular pleomorphism and signet ring cell appearance Fig. 5.25. Acinic cell carcinoma, papillary subtype: papillae are lined with intercalated duct-like cells, some containing microvesi- cles, others showing a hobnail/clear cell appearance and centenarians. The parotid is involved in 92% of cases (3% bilateral), with only occasional examples in the submandibular or minor glands , or periparot- id lymph nodes . The typical clinical history is of a slowly enlarging mass (for as long as 40 years) some- times with pain and facial nerve weakness. Most tu- mours are partly circumscribed, with a diameter of 10– 30 mm, although some may reach 220 mm . Micros- copy shows one or more growth patterns – solid, mi- crocystic, follicular and papillary-cystic. The follicular pattern resembles thyroid tissue, and any tumour in the parotid with a papillary-cystic architecture should be considered to be an AcCC, until proven otherwise. The cells in AcCC may take one of several forms – aci- nar (serous or blue dot), intercalated ductal (cuboidal, often lining small ducts), microvesicular, hob-nail or clear – the last is surprisingly rare, being seen in only 6% of cases . Several growth patterns and cell types may be seen in any individual tumour (Figs 5.24–5.26). Dedifferentiation towards a high-grade malignancy occurs occasionally , and all surgical specimens of AcCC must be sampled adequately. A lymphoid infil- trate is found in about 30% of cases, but is only of clin- ical significance (having a good prognosis) when the tumour is a well-circumscribed nodule with a micro- follicular architecture (Fig. 5.27) . The most useful special stain in AcCC is PASD, which highlights cytoplasmic zymogen granules (Fig. 5.28). Immunohistochemistry is of limited val- ue – positivity is seen with cytokeratin, amylase, CEA and in 10% S-100 protein . Other myoepithelial markers are negative. It has been suggested that bone morphogenetic protein-6 (BMP-6) may be useful, but this marker is not yet widely available . Electron
146 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo 5 Fig. 5.26. Follicular variant of acinic cell carcinoma: the tumour is composed of follicle-like spaces of varying sizes lined with cu- boidal intercalated duct-type cells Fig. 5.28. Acinic cell carcinoma. PAS-D emphasises coarse zy- mogen granules in the cytoplasm of the tumour cells that Ki-67 (MIB1) is an independent prognostic indi- cator [94, 198]. Skálová et al. found that tumours with a proliferation index <5% were cured by complete ex- cision, whereas more than half of AcCCs with indices above this either recurred or metastasised . The most effective treatment is complete surgical excision of the primary. Radiation may have a role if this is not possible. 5.9.2 Mucoepidermoid Carcinoma ICD-O:8430/3 Mucoepidermoid carcinoma (MEC) demonstrates a wide age distribution with a mean of 45 years. Pa- tients with tumours in the palate tend to be younger than those with tongue lesions. It is also the common- est salivary malignancy in children, and can be seen in patients as young as 4 years old . There is a slight 3:2 female predominance. It can occur in either ma- jor or minor glands. MEC is “a tumour characterised by the presence of mucus-producing cells, epidermoid cells and cells of intermediate type”. The proportion of the different cell types and their architectural con- figuration (including cyst formation) vary between tu- mours and sometimes within any individual neoplasm. Mucous cells tend to be more numerous in MECs with cyst formation. Mucous cells are cuboidal, columnar or goblet-like and form solid masses or line cysts, where they may be single or multi-layered . The mu- cin stains with PASD, Alcian blue and mucicarmine, and these are particularly useful in cases where mu- cus cells are few. Mucus-filled cysts may rupture and elicit an inflammatory response. Epidermoid cells usu- ally have intercellular bridges, but it should be noted that the term epidermoid does not indicate squamous differentiation, but simply a squamous-like appear- Fig. 5.27. Acinic cell carcinoma with lymphoid stroma: a charac- teristic microcystic appearance of this tumour subtype is seen microscopy shows multiple, round, electron-dense cy- toplasmic secretory granules . The differential di- agnosis depends on the subtype: serous cells resemble normal parotid acini, but with an abnormal architec- ture. The papillary-cystic type bears a close similari- ty to the controversial entity cystadenocarcinoma. A follicular pattern suggests metastatic thyroid carcino- ma, but is thyroglobulin-negative. The clear cell vari- ant must be differentiated from other neoplasms com- posed of clear cells, but there are always some cells with PASD-positive granules. AcCC is a genuine ma- lignancy capable of killing, although this may take many years. Average figures for recurrence are 35% and death from disease 16% . Several unsuccess- ful attempts have been made to predict the clinical out- come of AcCC from morphology, as even the blandest of tumours may cause death. Two studies have shown
147 Chapter 5 Major and Minor Salivary Glands Fig. 5.29. Mucoepidermoid carcinoma: clear, intermediate and mucus-secreting cells Fig. 5.31. High-grade mucoepidermoid carcinoma: “epidermoid” cells arranged in a solid pattern also show nuclear pleomorphism. Mucus-secreting cells may be scarce predict outcome to some degree, and MECs should be given one of three microscopic grades, based on the ex- tent of the cystic component, neural invasion, necrosis, cytological pleomorphism and mitotic activity. This assessment has considerable prognostic significance, with death rates due to disease of 3.3, 9.7 and 46.3% for grades 1, 2 and 3 respectively . Recently, a new grading system has been proposed, but it is still under evaluation . Assessment of the MIB1 proliferation index has also been shown to be of value . 5.9.3 Adenoid Cystic Carcinoma ICD-O:8200/3 Adenoid cystic carcinoma (AdCC) is a malignant tu- mour with no particular age or sex predilection. It can occur in any gland, but most often in the submandibular or minor salivary glands, particularly the palate. How- ever, in spite of often apparently slow growth, outcome over the long term is poor. AdCC is an extensively infil- trative tumour with characteristic perineural invasion, and this is partly responsible for the clinical presenta- tion of late, but repeated local recurrences. Unlike other salivary gland malignancies, when AdCC metastasises, it tends to involve distant organs (lung, bone) rather than local lymph nodes . Histologically, AdCC is a generally solid tumour in which the cribriform pattern is easily recognised on mi- croscopy, but tubular and solid structures can also be present. The commonest growth patterns are: Cribriform: this is the most characteristic microscop- ic feature, dominated by multiple cribriform structures, composed of epithelial and basal/myoepithelial cells. The nuclei are usually dark, hyperchromatic and angu- lated. Mitotic figures are easy to find and may be abun- Fig. 5.30. Low-grade mucoepidermoid carcinoma: typical cystic and solid pattern ance (Figs. 5.29–5.31). In fact, keratinisation is very rare in MEC, and indeed is much commoner as part of squamous metaplasia in pleomorphic adenoma or malignant myoepithelioma, and in metastatic squa- mous carcinoma from the skin or upper aerodigestive tract. Epidermoid cells may be sparse in MECs, and high molecular weight cytokeratin stains (e.g. LP34) and p63 can help identify them. Intermediate cells are small with dark-staining nuclei and they often form the stratified lining of cysts beneath the mucous cells. Clear cell change may be seen in either the squamous or intermediate cells and MEC may take the form of a clear cell carcinoma . Similarly, oncocytes can be plentiful . All MECs are malignant with a meta- static potential, regardless of their microscopic appear- ance. Nevertheless, histological features can be used to
148 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo 5 Fig. 5.32. Adenoid cystic carcinoma, cribriform variant: multiple cribriform spaces composed of basaloid cells, with hyalinised ma- terial surrounded by small hyperchromatic cells Fig. 5.34. Adenoid cystic carcinoma, solid variant. Th is is com- posed of multiple solid nodules, some displaying central comedo- like necrosis. Th e tumour can be seen to infi ltrate bone Fig. 5.33. Adenoid cystic carcinoma, cribriform variant. Diff use hyalinisation with compression of tumour cells. Nuclear pleomor- phism may be diffi cult to appreciate, leading to a false diagnosis of pleomorphic adenoma Fig. 5.35. Adenoid cystic carcinoma, solid variant. Tumour is- lands contain small ducts lined with a layer of epithelial cells. In the absence of characteristic cribriform structures, the latter fea- ture is diagnostic Solid (basaloid): this is dominated by large solid sheets of tumour cells, sometimes with comedo-like central necrosis. Within the solid masses of tumour cells, there are small duct-like spaces surrounded by a definite lay- er of epithelial cells (Figs. 5.34, 5.35). This latter finding distinguishes solid variant AdCC from (relatively low- grade) basal cell adenocarcinoma and the aggressive ba- saloid squamous cell carcinoma, which in addition often shows intraepithelial dysplastic changes. A rare finding in all types of AdCC is squamous metaplasia, either as single cells or with keratin pearl formation . A system of three grades based on the presence of tubular, cribriform and solid pattern  has shown dant; the MIB1 proliferation index exceeds 10% . The contents of the spaces can be loose and basophil- ic or dense and eosinophilic. Hyalinisation is common in adenoid cystic carcinoma and may be extreme. In those cases with excessive deposition of hyalinised ma- terial, the spaces are distended with loss of the cribri- form pattern. Tumour cells may be sparse and bland, and thus the lesions may mimic a pleomorphic adeno- ma (Figs. 5.32, 5.33). Tubular: this is composed of small tubules lined with one or two cell types, luminal and abluminal without significant cytological atypia. Because of this bland cy- tological appearance it may be mistaken for basal cell adenoma, except for the presence of infiltration.
149 Chapter 5 Major and Minor Salivary Glands that outcome is better in tubular ACC, while the worst prognosis is seen in solid AdCC. Nevertheless, clini- cal stage appears to be a better predictor than grade . Another unfavourable feature of AdCC is the fre- quent involvement of resection margins in the surgical specimen, particularly as the result of extensive perineu- ral infiltration. As complete excision of AdCC is diffi- cult, patients often require postoperative radiotherapy. A most important histological differential diagnosis is between AdCC and polymorphous low-grade adeno- carcinoma (see Sect. 5.9.4). Fig. 5.36. Polymorphous low-grade adenocarcinoma. Perineural infi ltration. Tumour cells show bland cytonuclear abnormality 5.9.4 Polymorphous Low-Grade Adenocarcinoma ICD-O:8525/3 Polymorphous low-grade adenocarcinoma (PLGA) is also known as terminal duct or lobular carcinoma. It is more frequent in women, and the average age at presen- tation is 59 years (range 21–94) . Most cases arise in intra-oral minor salivary glands, particularly the palate, with only rare examples in the parotid, sometimes de- veloping into a pleomorphic adenoma . The char- acteristic histological picture of PLGA is an infiltrating tumour with cytological uniformity and morphological diversity . The architecture comprises a variety of patterns, including ducts, streams, and micropapillary, cribriform and solid structures (Fig. 5.36). Diffuse infil- tration of tumour cells with Indian filing and concentric growth around nerves is reminiscent of lobular carci- noma of the breast (Fig. 5.37). The cells each have single regular round, ovoid or fu- siform bland nuclei, sometimes with intra-nuclear vac- uoles  and absent or small nucleoli. Variably pres- ent are oncocytic, clear or mucous cells. Mitotic figures are scanty, and never atypical. The stroma varies from fibromyxoid to densely hyaline, but the chondroid ma- trix of a pleomorphic adenoma is not seen. Immuno- histochemistry shows positivity with epithelial markers (cytokeratins, EMA), S-100, bcl-2 and sometimes CEA, ?SMA and vimentin ; MIB1 proliferation is low – mean 2.4% (range 0.2–6.4) in one study . PLGA behaves as a low-grade malignancy; a literature review found a recurrence rate of 21%, regional nodal metasta- sis in 6.5%, distant metastasis in 1.8%, and death due to cancer in 0.9% . However, after 10 years late recur- rences and metastases are perhaps more common than that , although in another study with a long follow- up, recurrence was in large part due to incompleteness of excision – none of the 22 excised tumours recurred or caused death . In a larger series of 164 PLGA, more than 95% of the patients had no evidence of dis- ease after a long-term follow-up . The recommend- Fig. 5.37. Polymorphous low-grade adenocarcinoma. Indian fi l- ing appearance resembling lobular carcinoma of the breast ed treatment of PLGA is wide, but conservative surgi- cal excision, postoperative radiation and chemotherapy have little place. The most important histopathological differential di- agnosis is from the much more aggressive adenoid cys- tic carcinoma. Although both are diffusely infiltrating carcinomas that display morphological diversity, at a cy- tological level the nuclei in AdCC are seen to be hyper- chromatic, angulated, pleomorphic and densely packed with more frequent mitotic figures, in contrast to the nuclei in PLGA, which are uniform with finely speckled chromatin. In addition, staining with S-100 protein is usually more diffuse and stronger in PLGA than AdCC [201, 225]. Other markers such as c-kit (CD117) are of little use in practice, as staining can be seen in AdCC and most PLGAs . Much more reliable marker is the MIB1 proliferation index, which is almost always signif- icantly lower in PLGA [201, 225]. Other differential di- agnoses include pleomorphic adenoma, which in minor salivary glands can be poorly circumscribed. The pres- ence of chondroid matrix and any circumscription fa-
150 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo 5 Fig. 5.38. Cribriform adenocarcinoma of the tongue (CAT). A vaguely nodular growth pattern is composed of solid nests with tubular structures Fig. 5.39. Epithelial myoepithelial carcinoma (EMCa): character- istic biphasic appearance with an inner layer of ductal cells and outer layer of clear myoepithelial cells. Basal membrane-like ma- terial surrounds the outer cells vours PA, but it is sometimes not possible to distinguish these tumours, particularly on a small biopsy. Papil- lary structures form part of the spectrum of growth pat- terns seen in PLGA , but when extensive, there is evidence that these tumours are slightly but significant- ly more aggressive [63, 64], although they do not seem to affect long-term survival. Genuine high-grade malig- nancy can occur rarely, as either a poorly differentiated PLGA or as a salivary duct carcinoma . one cell layer. Cytologically, there is one cell type; char- acteristically, the nuclei, which often overlap one anoth- er, are pale and vesicular with a “ground glass” quali- ty, thus resembling those of papillary thyroid carcino- ma (Fig. 5.38). Each nucleus can contain up to three nucleoli of vary- ing conspicuousness. Immunohistochemically, a strong or patchy reaction is seen with cytokeratins and S-100 protein. Actin, calponin and smooth muscle myosin heavy chain react with only a few areas. They are com- pletely negative for thyroglobulin. Patients treated with surgical excision and subse- quent irradiation have a good chance of prolonged sur- vival without recurrence or further metastatic spread . 126.96.36.199 Cribriform Adenocarcinoma of the Tongue ICD-O:8525/3 A newly described tumour  found so far only in the tongue, shares some histological features with PLGA, to which it is probably related. Cribriform adenocarci- noma of the tongue (CAT) usually arises in adults with a mean age of 50 years and equal sex incidence in the root of the tongue. Generally, at the time of diagnosis there are metastases in the neck lymph nodes, either unilaterally or bilaterally, but distant spread has not been described. Microscopic examination shows lobules divided by fibrous septa, composed of areas with solid and micro- cystic growth patterns. In the solid areas, tumour nests often display a well-developed hyperchromatic outer layer with a perpendicular arrangement of cells. This layer is frequently detached, forming papillae or glomer- uloid structures surrounded by apparent clefts. The mi- crocystic growth pattern is composed of lobules of neo- plastic cells with a cribriform and/or tubular architec- ture, the two patterns often intermingling. Typically, the tubules are approximately of the same size and consist of 5.9.5 Epithelial-Myoepithelial Carcinoma ICD-O:8562/3 The mean age at diagnosis of epithelial-myoepithelial carcinoma (EMCa) is 60 years (range 8–103), with a small majority in females . It occurs predominantly in the parotid gland, less often in the submandibular gland, occasionally in minor salivary glands and rarely in the bronchus . The microscopic appearance is characterised by small ductular lumina lined with two layers of cells (Fig. 5.39). The inner comprises cy- tokeratin-positive epithelial cells, and it is surrounded by an outer mantle of often clear myoepithelial cells, which express ?SMA, smooth muscle myosin heavy chain and calponin. S-100 protein also stains the outer cells strongly, but is less specific and sometimes reacts with the inner layer  – CK 14 appears to be un-
151 Chapter 5 Major and Minor Salivary Glands helpful. The outer cells are in turn surrounded by a rim of PAS-positive basement membrane material of vari- able thickness. This pattern is reproduced throughout most of the tumour, though each element may vary in prominence both between and within each lesion. Grossly, the tumours often appear to be well circum- scribed, but microscopy usually reveals some invasion of surrounding structures. Cytological pleomorphism is infrequent, but mitotic figures may be numerous. The stroma is usually scanty, but on occasions it con- sists of plentiful hyaline basement membrane material with relatively inconspicuous bilayered ducts; the tu- mour can then be mistaken for a pleomorphic adenoma . Other differential diagnoses encompass a wide range of salivary neoplasms, mainly those composed of clear cells, both primary and metastatic. Many salivary tumours can be diagnosed purely on H&E morphol- ogy, but clear cell lesions are an exception, and most re- quire immunohistochemistry and sometimes electron microscopy. EMCa can occasionally dedifferentiate as a high-grade adenocarcinoma  or a sarcomatoid spindle cell neoplasm of myoepithelial type . That they originate from intercalated ducts is supported by an unusual case of a typical EMCa in a parotid gland, which also contained multiple nodules of intercalated duct hyperplasia (Figs. 5.40–5.42) . This appearance may explain why EMCa is not in- frequent in hybrid tumours [31, 37]. The behaviour of EMCa is generally considered to be low grade, and in a literature review of 67 cases, recurrences were noted in 31%, cervical lymph node metastasis in 18%, distant metastasis in 7% and death due to tumour in 7% . In contrast, the series of Fonseca and Soares  found that 50% of neoplasms recurred and 40% of patients died of cancer. The only morphological feature found to corre- late with a poor prognosis was nuclear atypia in more than 20% of tumour cells. In another study DNA anal- ysis has shown that aneuploidy is associated with an in- creased chance of recurrence . Figs. 5.40–5.42. Intercalated duct hyperplasia of the parotid gland. Top: Hyperplastic foci are composed of an inner layer of epithelial cells surrounded by myoepithelial cells with ample and clear cytoplasm. Th e former stain for CAM5.2 (lower) and the lat- ter for smooth muscle actin (middle) 5.9.6 Hyalinising Clear Cell Carcinoma ICD-O:8310/3 Monomorphic clear cell carcinomas are either epithe- lial or myoepithelial (clear cell malignant myoepithe- lioma). The former, now known as hyalinising clear cell carcinoma was first described by Škorpil in Czech and German  and was rediscovered recently [138, 193], but was not included in the revised WHO classification . It usually arises in the minor glands and is of low- grade malignancy. Microscopically, it is characterised by groups and trabeculae of polygonal glycogen-rich cells separated by dense collagen bands. At times, particu- larly in the deeper parts of the tumours, the cells may lose their clarity when their cytoplasm appears weakly eosinophilic. Immunohistochemistry reveals positivity with epithelial markers (e.g. cytokeratin), but myoepi- thelial markers (e.g. S-100 protein and ?SMA) are nega- tive . 5.9.7 Basal Cell Adenocarcinoma This tumour has the architecture and cytology of basal cell adenoma, but displays infiltration. Most cases arise
152 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo amount of basement membrane material varies, but can be marked, especially in the membranous variant. Occasional cases show cytological pleomorphism, but generally this is absent, and mitotic figures are usually sparse. The most reliable indicator of malignancy is in- filtration of the surrounding gland, and less frequently of blood vessels and nerves (Fig. 5.43) . In addition, the Ki-67 proliferation index is usually higher in basal cell adenocarcinoma than its benign counterpart (>5% vs. <2.7%) . More than half the carcinomas in one study expressed p53, and 3 out of 11 cases were posi- tive for epidermal growth factor receptor (EGFR); in contrast, all the adenomas were negative . The differential diagnosis of basal cell adenocarcinoma includes solid forms of adenoid cystic carcinoma (see Sect. 5.9.3), which are much more aggressive neoplasms with cytological pleomorphism and plentiful mitot- ic figures; these are generally associated with other growth patterns such as small luminal structures. The behaviour of most basal cell adenocarcinomas is low grade. A review found an incidence of local recurrence of 37%, cervical lymph node metastasis of 8%, distant metastases of 4% and one patient died of disseminated disease . 5 Fig. 5.43. Basal cell adenocarcinoma. In spite of the lack of signif- icant cellular atypia, the infi ltrative pattern is diagnostic of malig- nancy. Courtesy of Prof. J.W. Eveson, Bristol, UK 5.9.8 Myoepithelial Carcinoma (Malignant Myoepithelioma) ICD-O:8982/3 Myoepithelial carcinoma is defined as a malignant epi- thelial neoplasm in which the predominant differen- tiation of the tumour cells is myoepithelial . The average age of patients at presentation is about 55 years (range 14–86), and the sex incidence is approximately equal. Most cases arise in the parotid, but they also oc- cur in the submandibular and minor glands [62, 168]. They may arise de novo, but at least 50% develop in a pre-existing pleomorphic adenoma or benign myoepi- thelioma [2, 54, 149, 168]. Macroscopically, malignant myoepitheliomas are uncircumscribed masses usually 20–50 mm in diam- eter (maximum 250 mm). The microscopic architec- ture is often multinodular with infiltration into adja- cent tissues. The nodules comprise solid and sheet-like growths of tumour cells often with plentiful myxoid or hyaline material, and sometimes displaying central ne- crosis (Figs. 5.44, 5.45). The range of cell types reflects that seen in benign myoepitheliomas and includes epi- thelioid cells (the most frequent) often arranged in tra- becular or pseudo-acinar structures with cleft-like spac- es. Cells with clear cytoplasm or vacuolation (resem- bling lipoblasts) and cells with hyaline (plasmacytoid) and spindle to stellate forms are also seen (Fig. 5.46). In most malignant myoepitheliomas one cell type predom- Fig. 5.44. Myoepithelial carcinoma. Multiple nodules infi ltrate dense fi brous tissue in patients over 50 years of age, and there is an equal sex incidence . The usual site is the parotid gland, but they have been described in the submandibular [131, 144], sublingual  and minor glands . They can arise de novo, but about 25% develop in a pre- existing basal cell adenoma , usually of the mem- branous type  (see Sect. 5.8.3). Microscopically, the general morphological and cytological appearances are almost identical to basal cell adenoma and likewise, four growth patterns are recognised – solid, tubular, trabecular and membranous – although these are not thought to have prognostic significance. The tumour islands contain a mixture of large, paler and small ba- saloid cells, with the latter usually demonstrating pe- ripheral palisading, though this is less marked than in the benign counterpart. The large cells sometimes form eddies, and the tumour islands may also contain small tubules and foci of squamous metaplasia. The
153 Chapter 5 Major and Minor Salivary Glands Fig. 5.45. Myoepithelial carcinoma, solid growth pattern with central necrosis in one of the nodules. Th is fi nding may mimic salivary duct carcinoma with comedo-like necrosis Fig. 5.47. Myoepithelial carcinoma: focal squamous metaplasia with keratin pearl formation Special stains in tumours without any ductal dif- ferentiation show no mucicarmine-positive mucus, but plentiful glycogen is found in clear cells and the myxoid matrix is positive with Alcian Blue. Metaplas- tic changes are frequent and include areas showing squamous differentiation, often with keratinisation (Fig. 5.47). Perineural invasion is seen in 44% and vas- cular invasion in 16%. In one series, 40% of tumours were categorised as high grade and 60% as low grade . All tumours show some positivity for S-100 pro- tein, vimentin and broad-spectrum cytokeratin (e.g. AE1-AE3 or MNF116). Other cytokeratin antisera (CAM 5.2 and LP34) show some reactivity in most tu- mours, and about half display some expression of cyto- keratin . Of the more specific myoepithelial mark- ers, approximately 75% of tumours including those composed of plasmacytoid cells, express calponin and about 50% are positive with αSMA; p63 was positive in 60% . Amongst other markers, glial fibrillary acidic protein (GFAP) is positive in 31% and epithe- lial membrane antigen (EMA) in 20%, in addition to highlighting any true small ducts, but carcino-embry- onic antigen (CEA) is usually negative. CD117 (c-kit) was positive in the few cases studied . The mean MIB1 (Ki-67) index in one series was 35% (range 15– 65), with any count above 10% said to be diagnostic of malignancy in a myoepithelial neoplasm . Electron microscopy shows that some tumour cells contain small desmosomes, but actin filaments are few . It has been shown that malignant myoepithelio- mas secrete matrix-degrading proteinases, as well as proteinase inhibitors , and this appears to be as- sociated with demonstrated inhibition of angiogenesis. These features indicate an anti-invasive effect, and al- though as yet poorly understood, this is likely to have Fig. 5.46. Myoepithelial carcinoma. Th e spindle cell component shows nuclear pleomorphism resembling a soft tissue sarcoma. A helpful diagnostic pointer is that other types of myoepithelial cell are usually identifi ed elsewhere inates, but there is usually a minor component of oth- er cell types. No true glands or lumina are seen in pure, malignant myoepitheliomas, but as with their benign counterparts, occasional small ducts in a neoplasm with otherwise typical features should not preclude the diag- nosis . The nuclei can vary from relatively uniform, small with finely distributed chromatin, lacking obvious nucleoli, to markedly enlarged and pleomorphic, show- ing chromatin clumping and large nucleoli. Mitotic fig- ures may be plentiful (range 3 to 51 per 10 high power fields) and include atypical forms . Multinucleate  and bizarre tumour giant cells may occasionally be present. The tumour-related matrix is generally promi- nent and is hyalinised or myxoid.
154 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo Table 5.3. Classifi cation of clear cell tumours and tumour-like conditions of the salivary glands  Benign Pleomorphic adenoma Myoepithelioma Sebaceous adenoma Oncocytoma Multifocal nodular oncocytic hyperplasia (MNOH) Mucoepidermoid carcinoma Acinic cell carcinoma Malignant, primary (carcinomas not usually characterised by clear cells, but with rare clear cell variants) Malignant, primary (carcinomas usually characterised by clear cells) Epithelial-myoepithelial carcinoma Hyalinising clear cell carcinoma Clear cell malignant myoepithelioma (myoepithelial carcinoma) Sebaceous carcinoma Carcinomas: especially kidney, thyroid. Also melanoma 5 Malignant, metastatic an effect on the biological aggressiveness of any partic- ular tumour. The variable appearance of malignant myoepitheli- oma, leads to a wide differential diagnosis, including other salivary carcinomas. Nodules with central necro- sis mimic the comedocarcinoma structures in salivary duct carcinoma, but there is usually more stromal ma- terial in the myoepithelial neoplasm and in addition, S- 100 and/or myoepithelial markers are usually positive. The clear cell variant resembles many other salivary neoplasms composed of clear cells, benign and malig- nant, primary and metastatic (Table 5.3) [132, 174] (see Sect. 5.9.5). The prognosis of malignant myoepithelioma is vari- able, but approximately one-third of patients die of dis- ease, another third have residual tumour and the re- maining third are disease-free [62, 168]. When metas- tases occur, they can be found in neck lymph nodes and at distant sites, including lungs, kidney, brain and bones. Malignant myoepitheliomas arising in ordinary pleomorphic adenomas behave in the same way as those that arise de novo , but it has been suggested that neoplasms developing in multiply recurrent pleomor- phic adenomas may pursue a prolonged course . A further suggestion is that malignant myoepitheliomas composed mainly of plasmacytoid cells may be more ag- gressive [53, 218]. However, Savera and Sloman in their series of 25 cases found only a weak statistical correla- tion for outcome with cytological atypia (high grade), but other parameters (tumour size, site, cell type, mitot- ic rate, presence of a benign tumour, necrosis, perineu- ral and vascular invasion) showed no relationship . In practice with any particular case, the various histo- logical features should be listed, and an attempt made to describe the tumour as low- or high-grade, but adding a rider that histological grade is as yet a far from proven guide to clinical behaviour. Treatment is surgical, and no role for radio- and chemotherapy has yet been estab- lished. 5.9.9 Salivary Duct Carcinoma ICD-O:8500/3 Salivary duct carcinoma (SDC) is probably not as un- common as previously thought [87, 93]. Most patients are over 50 years old and there is at least a 3:1 male pre- dominance. It arises mainly in the parotid, less often in the submandibular gland and only occasionally in the minor glands of the palate , buccal mucosa , maxilla  and larynx . It can develop de novo or in a pre-existing pleomorphic adenoma [86, 87] or polymorphous low-grade adenocarcinoma . The microscopic appearance of SDC bears a striking resem- blance to ductal carcinoma of the breast, both in situ and invasive, where all of the features of the mammary equivalent can be reproduced (Fig. 5.48). Perineural and lymphovascular invasion are seen in many cases. Nucle- ar pleomorphism is usual, and is also apparent on FNA cytology . Mitotic figures are often numerous, also reflected in a high Ki-67 proliferation index . Although most cases of SDC can be diagnosed with HE alone, special stains can help in a few instances. Im- munohistochemistry shows expression of epithelial mark- ers such as cytokeratins (including subtype 7, but not 20), EMA and GCDFP-15. S-100 protein is usually negative, as are myoepithelial markers, although they may highlight subtle in situ lesions . Despite the morphological simi- larity to breast carcinoma, staining for oestrogen and pro- gesterone receptors is almost always negative, in contrast to that for androgen receptors (AR), where >90% of SDCs react, even in women. AR positivity appears to be specif- ic to SDC (including when it arises in a pleomorphic ad- enoma), and is not seen in for example, mucoepidermoid
155 Chapter 5 Major and Minor Salivary Glands Fig. 5.48. Salivary duct carcinoma: invasive irregular ducts and cribriform structures strongly resemble ductal carcinoma of the breast Fig. 5.49. Salivary duct carcinoma, mucin-rich variant. Th is is composed of a mixture of usual-type salivary duct carcinoma and lakes of mucinous adenocarcinoma carcinoma . Some studies have shown SDCs to ex- press prostate specific antigen (PSA) or acid phosphatase [110, 120], but another failed to confirm this  and similarly, only 1 out of 40 cases in a Mayo Clinic series was PSA-positive . More recently cases of SDC show- ing positive staining for HER-2/neu (c-erbB-2) protein on immunohistochemistry have been published , and the gene amplification has been demonstrated with FISH analysis . Several rare morphological variants of SDC have been described, including cribriform , micropapil- lary , sarcomatoid , mucin-rich  and on- cocytic (Figs. 5.49, 5.50) . So-called low grade sal- ivary duct carcinoma  is probably a separate entity (see below). The differential diagnoses of SDC are high-grade mucoepidermoid carcinoma, oncocytic carcinoma and some metastases. The diagnosis of mucoepidermoid carcinoma requires the presence of squamous-like cells, mucus-producing cells and cells of intermediate type, and there is no expression of androgen receptors. Many salivary oncocytic carcinomas probably demonstrate other types of malignancy (including SDC) with plenti- ful oncocytic cells, but a true oncocytic carcinoma lacks any features of SDC and is AR-negative. At present, nei- ther of these two differential diagnoses is clinically crit- ical since the prognosis is similar. However, it is impor- tant to identify metastatic carcinoma, particularly from the prostate or breast. In most cases, metastases will be obvious from clinical investigation and imaging studies, but the usual immunoprofile of these tumours is differ- ent: prostatic carcinomas tend to be AR+, ER−, PSA+, CK 7+; breast carcinoma tend to be usually AR−, often ER +, PSA−, CK 7+; SDC is AR+, ER−, usually PSA−, and CK 7+. Fig. 5.50. Salivary duct carcinoma with oncocytic diff erentia- tion. Th e cells have ample granular cytoplasm with vesicular nu- clei and prominent nucleoli. A clear distinction between oncocyt- ic salivary duct carcinoma and true oncocytic carcinoma may not be possible, as they may not be separate entities The prognosis for SDC is poor, and most series have shown that more than 70% of patients die of disease, usually within 3 years. Nevertheless, Grenko et al.  alluded to a minority (about 25–30%) who do well, but their study was unable to identify any particular features of this group. Amongst possible prognostic indicators, tumour size is probably important, with lesions <30 mm in diameter having a better prognosis , but never- theless several fatal lesions of 20 mm have been report- ed [23, 36, 87, 185]. Determination of tumour DNA ploi- dy has not been found to have prognostic significance [9, 86], but it is possible that MIB1 proliferative activ- ity might do so . At present, the best hope for long- term survival appears to be complete surgical excision
156 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo with radical neck dissection followed by radiotherapy to the tumour bed and chemotherapy [36, 145]. The recent identification of androgen receptors expression in SDC raises the question as to whether anti-androgen ther- apy (e.g. flutamide or goserelin) might have merit [99, 142, 153]. The significance of staining for HER-2/neu (c- erbB-2) protein is at present uncertain [202, 204], either prognostically or for planning therapy with herceptin. The entity “low grade salivary duct carcinoma (low grade cribriform cystadenocarcinoma)” has a predomi- nantly intraductal growth pattern with low-grade cyto- logical features , and its relationship to usual-type SDC is as yet uncertain. The tumour is S-100-positive and the only case studied for AR was negative . The prognosis is good, and although only a few cases have been described, none of the patients has died of dis- ease. overall, malignancy develops in 6.2% of all PAs (range in different series 1.9 to 23.3%). The incidence of ma- lignant change increases with the length of history of the PA, from 1.5% at 5 years to 10% after 15 years. The concept of malignant mixed tumour (MMT) as a malig- nant tumour that contains remnants of benign mixed tumour was developed by LiVolsi and Perzin in 1977 . Spiro et al.  agreed with this, but suggested a possible de novo origin in cases lacking a clinical his- tory or histological evidence of a pre-existing salivary gland tumour. The revised WHO classification of salivary gland tu- mours  discussed the topic of MMT with the title Carcinoma in Pleomorphic Adenoma and the sub-title Malignant Mixed Tumour. Three entities are recognised: carcinoma in pleomorphic adenoma, carcinosarcoma (true malignant mixed tumour) and metastasising pleo- morphic adenoma . There is no uniform agreement on this classification as metastasising PA does not con- tain histological features of malignancy and therefore it is anomalous to include it as a form of malignancy in PA. In addition, not all carcinosarcomas arise from a PA. Final- ly, the possibility of myoepithelial malignancy arising in a PA is not included . 5 5.9.10 Oncocytic Carcinoma ICD-O:8290/3 Several carcinoma types have variants composed of oncocytic cells, but only a few dozen cases of pure on- cocytic carcinoma have been reported. The average age is 63 years (range 29–91), and most have occurred in the parotid ; some have arisen in Warthin’s tu- mours . The diagnosis of a pure oncocytic car- cinoma requires the identification of malignancy, oncocytic differentiation and lack of features of any other tumour type. It is likely that a pure oncocytic carcinoma is an aggressive tumour, as over half of the patients reported either died of disease or suffered re- currences . 188.8.131.52 Carcinoma Ex Pleomorphic Adenoma ICD-O:8941/3 Two subtypes should be recognised: invasiveand non- invasive carcinoma. 184.108.40.206.1 Invasive Carcinoma Ex PA 5.9.11 Malignancy in Pleomorphic Adenoma Malignant Mixed Tumour This is the commoner form, in which the malignancy involves only the epithelial component. It occurs mainly in men over 60 years old. Most cases (81.7%) involve the parotid gland, with the submandibular in 18% and the sublingual in 0.3%; the minor salivary glands, particu- larly in the palate, can also be affected . The typical presentation is a long history of a salivary gland nodule that suddenly increases in size. The demonstration of both a carcinoma and a PA is necessary for the diagnosis. A history of a long-standing parotid tumour is not sufficient evidence for a pre-existing PA, whilst a pre- viously excised PA at the site of a carcinoma is accept- able . Grossly, carcinoma ex PA is often larger than a be- nign PA. Histological recognition of a pre-existing PA may be difficult, as it could be obscured by the carci- noma, or may only show degenerate changes such as The histological diagnosis of pleomorphic adenoma (PA; benign mixed tumour) is not always straightfor- ward, as benign lesions may display atypical histologic features such as capsular infiltration, hypercellularity, cellular atypia, necrosis and vascular invasion [3, 7], which cause suspected malignancy. In addition, some PAs contain genuine cytologically malignant cells, but behave in a benign fashion [21, 56]. A further paradox is the rare occurrence of histologically benign-looking PAs that metastasise . Thus, the concept of malig- nancy in PA is much more complex than appears at first sight. This is reflected by the variable incidence for the reported frequency of malignancy in PA. In several large series [83, 125, 149, 209, 223] the average was 3.6% of all salivary gland tumours and 11.7% of malignancies;
157 Chapter 5 Major and Minor Salivary Glands Fig. 5.51. Non-invasive carcinoma in a pleomorphic adenoma. Ducts contain cells with atypical nuclei. Focal necrosis and calci- fi cation is also present Fig. 5.52. True malignant mixed tumour/carcinosarcoma. Th e epithelial component is a poorly diff erentiated carcinoma with some features suggesting salivary duct carcinoma. Th e sarcoma- tous component is a high-grade spindle cell sarcoma, in this case, without specifi c diff erentiation 220.127.116.11.2 Non-Invasive Carcinoma Ex PA scarring, dystrophic calcification, necrosis and haem- orrhage with occasional transitional changes made up of cells showing features intermediate between frank malignancy and PA [49, 124]. Although the propor- tion of the malignant component varies from minute foci to almost the whole lesion, recognition of frank- ly invasive carcinoma ex PA is usually simple. Capsu- lar, perineural and vascular invasion are easily identi- fied, as well as extension into neighbouring tissues [49, 62, 124]. Recent studies show adenocarcinoma not other- wise specified and salivary duct carcinoma to be the most frequent histological types [49, 87], and there is immunohistochemical and ultrastructural evidence that many carcinomas previously described as “undif- ferentiated” are in fact myoepithelial – indeed many myoepithelial carcinomas can be shown to have aris- en in a pre-existing PA [52, 53, 151, 168]. It is not un- common to find other concurrent differentiation, e.g. squamous, mucoepidermoid, polymorphous low- grade adenocarcinoma [125, 149, 209]. In determining the prognosis, the extent of invasion is more impor- tant than the histological type: Tortoledo et al.  found that none of the patients whose tumour pene- trated <6 mm beyond the capsule died of disease, but that all patients with invasion of >8 mm died of dis- ease. A more recent study found that none of the tu- mours that invaded <5 mm beyond the host PA pro- gressed . In contrast to the aggressive behaviour of invasive carcinoma ex PA, tumours that contain only circum- scribed areas of malignancy confined within the cap- sule  behave in a benign fashion after excision (Fig. 5.51). In one series, four patients with intracap- sular (non-invasive) carcinoma all had a good clinical outcome . Brandwein et al.  confirmed this and also noted that the same benign behaviour applies for minimally invasive carcinoma ex PA. In contrast, there is a single report of metastases developing from a non-invasive carcinoma . In spite of the generally excellent behaviour, the cells in non-invasive carcino- ma ex PA display overexpression and amplification of HER-2/neu protein, and thus probably represent true carcinoma in an early phase rather than just bizarre cytological changes . This study also recommend- ed the use of HER-2/neu immunohistochemistry to distinguish between PAs with atypical cells and non- invasive carcinoma ex PA . 18.104.22.168 Carcinosarcoma (True Malignant Mixed Tumour) Ex Pleomorphic Adenoma ICD-O:8980/3 Only about 60 cases of carcinosarcoma (CS) true ma- lignant mixed tumour (TMMT) have been reported to date [83, 214]. Many arise in a pre-existing PA, but they can also develop de novo. As with carcinoma in a PA,
158 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo the history will usually be that of rapid growth in a long- standing salivary nodule. Microscopy shows a biphasic tumour composed of epithelial and mesenchymal elements. The former is generally a poorly differentiated (adeno)carcinoma, but salivary duct carcinoma is increasingly report- ed (Fig. 5.52) [49, 50]. The other component is usual- ly a chondrosarcoma, but osteogenic sarcoma, fibro- sarcoma, malignant fibrous histiocytoma, pleomor- phic rhabdomyosarcoma and osteoclast-type giant cell neoplasms [214, 224] have also been described. Epithelial markers are usually detected in the epi- thelial component, which may or may not also be ex- pressed in the sarcomatous component. Positive stain- ing for epithelial markers has been used as proof of the fact that CS are carcinomas showing divergent differ- entiation and as an indication of their monoclonal ori- gin. However, keratin staining can be negative casting doubt onto the monoclonal-carcinomatous nature of the whole tumour. Molecular studies have been help- ful in clarifying this issue. In analogous neoplasms in other organs such as breast, uterus and in salivary glands, molecular studies have demonstrated that car- cinomatous and sarcomatous components have simi- lar genetic profiles. Moreover, in a subset of CS with osteoclastic-type giant cells, Tse et al.  found mu- tation of the same allele on chromosome 17p13, which is a known mutation of salivary duct carcinoma. This indicates that carcinosarcoma are in fact carcinomas of high-grade malignancy and should be treated as such. HER-2 overexpression on immunohistochemis- try is also seen in the salivary duct component of CS. The meaning of this information has still not been clarified . metastases . Although the morphology of both is almost identical, the recurrences seem to play an im- portant role in the genesis of systemic spread. This sug- gests that surgical manipulation may favour vascular implantation or invasion eventually leading to metas- tases, but in many cases of MPA it was not possible his- tologically to demonstrate actual vascular permeation [56, 232]. 5.9.12 Sebaceous Carcinoma 5 ICD-O:8410/3 Although sebaceous glands are common in the oral mu- cosa (Fordyce granules), sebaceous neoplasms of the sal- ivary glands are rare. Most sebaceous carcinomas have arisen in the parotid , possibly from pluripotent duct cells . The sex incidence is equal, and the mean age is 69 years (range 17–93). Macroscopically, they are partly encapsulated and vary in size from 6 to 85 mm across the greatest diameter. Microscopy shows inva- sive islands, duct-like structures and sheets of tumour cells, which may be sebaceous, squamous or basaloid; intracellular mucin may be found . Sebaceous cells are present in varying numbers, and typically comprise foamy cytoplasm and a single vesicular nucleus with a prominent nucleolus. Areas of necrosis are frequent . The tumour cells react with cytokeratin and EMA, but not with S-100 protein or actin . The behaviour is intermediate to high-grade, and recurrences, metas- tases and death due to disease have all been reported. Three cases of sebaceous lymphadenocarcinoma have been described, representing malignant transformation of sebaceous lymphadenoma. One of the patients died because of the tumour . 22.214.171.124 Metastasising Pleomorphic Adenoma 5.9.13 Lymphoepithelial Carcinoma ICD-O:8940/0 This tumour is histologically indistinguishable from benign PA, yet it metastasises widely to sites including lymph nodes, bone, lung and kidney, and can kill the patient . Whereas the WHO revised classifica- tion lists metastasising pleomorphic adenoma (MPA) as one entity in the MMT category of , it differs because it remains histologically “benign” in the pri- mary site, local recurrences, and metastatic deposits [56, 232]. It is a rare tumour with fewer than 100 reported cas- es so far. Despite this, MPA has a clear-cut clinicopath- ological profile: the reported cases shared several simi- larities, such as long time intervals (up to 50 years) be- tween the primary tumour and metastases, and simul- taneous, usually multiple, local recurrences and distant ICD-O:8082/3 The WHO revised classification includes this tumour under undifferentiated carcinomas , but it is a gen- uine clinicopathological entity and can be considered separately. Lymphoepithelial carcinoma is extremely rare ex- cept in Eskimos (Inuit) and in Southern China. The median age is 40 years (range 10–86), and it is slightly commoner in females ; familial clusters have been identified amongst patients from Greenland . The parotid is involved in 80% of cases, with the rest occur- ring in the submandibular glands. Forty per cent of pa- tients have lymph node metastases at the time of pre- sentation. A few examples have been described in asso- ciation with lymphoepithelial sialadenitis , but a much more important association is with Epstein-Barr
159 Chapter 5 Major and Minor Salivary Glands Table 5.4. Metastases to the parotid gland, adapted from Gnepp  Location of primary Number of tumours Skin of head and neck Upper aero-digestive tract (mouth, nose, sinuses, pharynx) Eye (conjunctiva, lacrimal gland) Thyroid Head, not otherwise specified Central nervous system Submandibular salivary gland Lung Kidney Breast Colorectal Prostate Skin, distant Stomach Uterus Pancreas Total, distant sites Skin, not otherwise specified Unknown primary site 422 (53.8%) 63 6 5 4 4 1 28 23 19 7 4 3 2 1 1 88 (11.2%) 108 84 virus, and viral genomes can be detected in the malig- nant cells . There is a marked histological similarity to undif- ferentiated nasopharyngeal carcinoma, which has also been linked to Epstein-Barr virus. Microscopic ex- amination shows syncytial groups of large epitheli- al cells with vesicular nuclei and prominent nucleoli, intimately mixed with lymphocytes and plasma cells, sometimes with germinal centre formation. Mitotic figures are often numerous. At times, the epithelium is difficult to identify, but it can be highlighted by cy- tokeratin markers. The most important differential di- agnosis is a metastasis from a nasopharyngeal prima- ry, which can present as a parotid mass , or possi- bly very poorly differentiated squamous carcinoma of usual type originating in the skin or upper aerodiges- tive tract. The outcome is surprisingly good for such an aggressive-looking carcinoma, and the 5-year sur- vival rate is 60%. called small cell carcinoma may in fact be primary primitive neuroectodermal tumours . They are seen more often in men, and the mean age is 56 years (range 5–86) . The microscopic appearance may be similar to small cell carcinoma of the lung or Merkel cell carci- noma of the skin. Both comprise solid sheets, nests and cords of closely packed cells; the difference is in the cell size – small and dark cells in the former, slightly larger and with pale chromatin in the latter. Immunohistochemistry shows positive staining for chromogranin, synaptophysin, neuron-specific eno- lase and CAM5.2, often with paranuclear dots in both types. However, immunohistochemistry for cytokera- tin 20 seems to identify two subtypes of small cell car- cinoma: CK 20− lung cell type and CK 20+ Merkel cell type carcinoma. A recent study by Nagao et al.  showed that CK 20+ small cell carcinomas of the sali- vary glands have a better prognosis than CK 20− cas- es. This suggests that staining for CK 20 should be performed in SCC as the results may have prognostic value . The differential diagnosis includes metas- tasis from small cell carcinomas of the lung and this must be excluded before a primary small cell carcino- ma can be said to be of salivary origin. Lymphomas and primary primitive neuroectodermal tumours of the salivary glands [44, 105] may be somewhat simi- lar morphologically, and can be excluded immunohis- tochemically. 5.9.14 Small Cell Carcinoma ICD-O:8041/3 Small cell carcinoma (SCC) is unlikely to be a single entity, as electron microscopy reveals that some neo- plasms show neuroendocrine differentiation, whilst others have squamous and ductal features not appar- ent histologically [15, 118], and occasionally both pat- terns are evident in the same tumours. Some neoplasms
160 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo lial-myoepithelial carcinomas showed myoepithelial features. The processes underlying dedifferentiation of salivary neoplasms remain to be established, but previ- ous radiotherapy may have been important in some of the AdCCs  and PLGAs . In general, no defi- nite factors in the progression of low-grade to high- grade carcinomas have been identified at a molecular level ; for example, there is conflicting evidence regarding p53 mutations, which might have been in- volved in a single case of transformed AdCC , but was not a factor in dedifferentiated acinic cell carcino- mas [51, 95]. 5 5.9.16 Metastatic Malignancies Metastases to the major glands and the intraparotid lymph nodes constitute approximately 10% of all sali- vary carcinomas ; the exact figure varies from study to study depending on local factors such as dif- ferent incidences of particular cancers. For example, Bergensen et al.  in Australia reported that me- tastases constituted 72% of all malignancies, resulting from the high incidence of skin cancer. In an AFIP se- ries and literature review in 1991 of 785 parotid metas- tases , 64% were found to have originated from the head and neck region (including the skin), 11% from distant sites and 25% from an unknown primary. Of the distant sites, lung, kidney and breast accounted for more than four-fifths (Table 5.4); only four cases were from the prostate, but it is perhaps under-recognised . Metastases to the submandibular glands are less common than to the parotids, but are more likely to be from distant sites . Microscopically, metastases in the salivary glands can resemble almost any primary tumour, so that for example, mammary duct carcinoma is morphological- ly identical (but immunohistochemically different) to salivary duct carcinoma (see Sect. 5.9.9). Similarly, re- nal cell carcinoma is part of the differential diagnosis of any clear cell tumour of the salivary glands, and ex- amples of prostate carcinoma have been mistaken for acinic cell carcinoma . Immunohistochemistry is of some value, and can identify prostate and thyroid primaries and melanoma with a reasonable degree of accuracy. Unlike most primary malignant salivary tu- mours, renal cell carcinomas are usually negative with cytokeratin 7; in contrast, CD10 stains most kidney carcinomas, but is only positive in salivary tumours with myoepithelial differentiation. However, the pos- sibility of metastasis is still best confirmed or excluded by imaging techniques of the kidneys. Figs. 5.53, 5.54. Endodermal sinus tumour of the parotid gland. Positive staining for placental alkaline phosphatase (PLAP) is es- sential to confi rm the diagnosis. Courtesy of Dr. Isabela Wernicke  5.9.15 Higher Grade Change in Carcinomas High-grade transformation is a rare but well-estab- lished event in several primary low-grade salivary car- cinomas, and usually heralds a more aggressive clini- cal course. Examples have been described in acinic cell [51, 95, 154, 213], adenoid cystic [32, 140], epithelial- myoepithelial [2, 73, 186], mucoepidermoid  and polymorphous low-grade adenocarcinoma [160, 191], as well as malignant myoepithelioma . In each case, the diagnoses of high-grade change were based on histopathological criteria, especially increased mi- totic and proliferation rates. Most of the transformed components were poorly differentiated adenocarcino- mas, but some of those in adenoid cystic and epithe-
161 Chapter 5 Major and Minor Salivary Glands 5.10 Hybrid Carcinoma 5.13 Alterations in Gene Expression and Molecular Derangements in Salivary Gland Carcinoma Hybrid tumours are composed of two different types of tumour, each of which conforms to an exactly defined category of tumour. They are rare, comprising <0.1% of neoplasms in the Hamburg Salivary Tumour Registry . Malignant examples demonstrate various combi- nations, e.g. epithelial-myoepithelial and adenoid cystic carcinomas . Present classifications contain at least 17 different sali- vary malignancies that can be broadly subdivided into carcinomas with myoepithelial differentiation and car- cinomas with acinar/epithelial differentiation. Marker proteins including cell-proliferation antigens, myoepi- thelial proteins, matrix metalloproteinases, growth fac- tors and their receptors, and steroid receptors have been introduced for diagnosis and prognostication of specific types of salivary gland carcinoma . Despite advances, the genetic events associated with the development and progression of salivary gland neoplasia are largely unknown. There is a clear need for better understanding of such events, for defining new prognostic and diagnostic markers, and for de- signing targeted therapeutic interventions. The recent application of microarray technologies in the study of head and neck cancer, as well as other malignancies, has resulted in the generation of interesting new data [167, 216, 235]. Also, studies of microsatellite markers have identified losses of heterozygosity  and dif- ferences in chromosomal loci among various types of salivary gland carcinoma. 5.11 Endodermal Sinus Tumour ICD-O:9071/3 There are only two reports of primary endodermal si- nus tumour (EST) of the parotid gland. One that re- curred after chemotherapy occurred in a 2-year-old girl ; the other was seen in a 16-month-old girl, who is alive and well 2 years after chemotherapy . The serum AFP was elevated and returned to normal levels after surgical resection of the EST. As for EST in other sites, several patterns can be recognised . Diffuse positive staining for AFP and placental alka- line phosphatase (PLAP) by immunohistochemistry may be necessary to confirm the diagnosis (Figs. 5.53, 5.54) . 5.13.1 Predominantly Myoepithelial Malignancies 5.12 Sialoblastoma The commonest salivary gland malignancy express- ing myoepithelial properties is the adenoid cystic car- cinoma (AdCC). Abnormal gene expression of AdCC has been studied using oligonucleotide microarrays of 8,920 genes . The most overexpressed genes coded for basement membrane and extracellular matrix pro- teins of myoepithelial differentiation, such as laminin- ?1, versican, biglycan and type IV collagen-?1. Other overexpressed genes included transcription factors SOX-4 and the AP-2 family, and members of the Wnt/ beta-catenin signalling pathway such as casein kinase 1, epsilon and frizzled-7. The most underexpressed genes included in particular those encoding for secre- tory proteins of acinar differentiation such as amylase, carbonic anhydrase and salivary proline-rich proteins. In AdCC, loss of heterozygosity frequently occurs in chromosome 6q23-25, correlating with prognostic pa- rameters . In addition, altered gene expression in pleomorphic adenomas has been recently studied in cDNA microarrays . ICD-O:8974/1 This rare tumour of the major glands arises in the peri- natal period or in the first year of life . It is well cir- cumscribed, up to 150 mm in diameter and composed of numerous solid hypercellular islands of primitive basaloid cells, some with peripheral palisading, and often with small central ducts. The tumour cells have large round to ovoid vesicular nuclei and abundant eo- sinophilic cytoplasm, and immunohistochemistry and electron microscopy show both epithelial and myoepi- thelial cells . Mitotic figures may be numerous, but none is atypical. Criteria for malignancy include inva- sion of nerves or vascular spaces, necrosis and marked cytological atypia . Out of 15 reported cases, 4 had recurrences and another had metastases to regional lymph nodes.
162 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo 5.13.2 Predominantly Epithelial Malignancies Major salivary gland carcinomas with acinar/ductal epi- thelial differentiation include mucoepidermoid carcino- ma (MEC), acinic cell carcinoma (AcCC) and salivary duct carcinoma (SDC). Gene expression profiles have been determined in all three using Clontech’s cDNA arrays including 1,176 cancer-related genes . Only five such genes are overexpressed by all these carcinoma types including fibronectin (FN1), tissue metallopro- teinase inhibitor-1 (TIMP1), biglycan (BGN), tenascin C (HXB), andinsulin-like growth-factor binding protein- 5 (IGFBP5). Sixteen genes, i.e. KIAA0137/TLK1, VRK2, ADSL, CREBBP, PSM/FOLH, PIK3R1, PRKACB, BAG1, SMAD4/MADH4, TRAM, LAMA4, AKAP1, MAPK13, ATP5J, ATIC, and EPS15, are underexpressed in all of them. Average-linkage hierarchical clustering indicates genes that are significantly differently expressed among these carcinoma types. They were identified using sig- nificance analysis of microarrays (SAM). In hierarchi- cal clustering, low-grade and high-grade MECs clus- ter closely together, and separate from closely clustered SDC . A hierarchical clustering of SDC and ACC shows that each entity clusters together, and separates from the other entity. In SAM, 27 genes are significant- ly differently expressed between MEC and SDC . Five genes, i.e. MMP11, DAP12, KIAA0324, FASN and CASP10 are overexpressed by SDC, while eight genes, including IL-6 and KRT14 are overexpressed by MEC. Another 14 genes that are mainly involved in DNA modification, such as NME4, NTHL1, RBBP4, HMG17 and NDP52, are underexpressed by MEC. Quantitative RT-PCR confirms results including overexpression of FN1 and TIMP1, underexpression of PSM/FOLH1 and MADH4/SMAD4, as well as the difference of expression profiles of IL-6, CASP10 and KRT14 between SDC and MEC. Immunohistochemistry indicates distinct expres- sion of cytokeratin 14 in MEC, with no expression in AcCC and SDC . Furthermore, major differences between predomi- nantly myoepithelial and predominantly epithelial car- cinomas also exist. In MEC and AdCC, the expression of important effector molecules such as erbB-2, erbB- 3, epidermal growth factor receptor and transforming growth factor-? is largely dissimilar . The small number of similarly deregulated genes in these major types of salivary gland carcinoma sug- gests heterogenic mechanisms of tumorigenesis. This is consistent with the great histopathological diversity among carcinomas of the salivary glands . Diver- sity is also implicated by differences in gene expression among tumour types in hierarchical clustering. The small number of genes jointly overexpressed by major 5 Fig. 5.55. Lymphoepithelial sialoadenitis (LESA): lymphoepithe- lial lesions are cohesive aggregates of epithelial cells with hyalin- ised basal membrane-like material infi ltrated by lymphocytes salivary gland carcinomas with epithelial differentia- tion relate to cell adhesion, motility and cell shape (FN1, BGN, HXB), cancer growth, metastasis, tumour angio- genesis and apoptosis (TIMP-1, IGFBP-5). The jointly underexpressed genes include cell-cycle proteins, pro- teins of signal transduction and translation, and extra- cellular matrix and membrane proteins. Interesting- ly, the jointly underexpressed CREBBP and MADH4/ SMAD4 are intimately involved in the TGF-β tran- scription pathway of growth inhibition, and MADH4/ SMAD4 has been shown to be deleted or mutated in half of pancreatic carcinomas . Thus, overexpres- sion of TIMP1, PLAT and SFN [38, 178], and underex- pression of MADH4/SMAD4 are shared by carcinomas of the salivary glands and the pancreas, but not with other exocrine carcinomas. In the salivary glands, co- ordinated loss of SMAD4 and CREBBP functions could impair growth control and promote oncogenic trans- formation. 5.14 Benign and Malignant Lymphoid Infiltrates 5.14.1 Non-Autoimmune Lymphoid Infiltrates These can be considered in four groups – obstructive, infective, various non-infective inflammatory process- es, and associated with epithelial tumours, especially carcinomas (see Sect. 5.9).
163 Chapter 5 Major and Minor Salivary Glands Table 5.5. Overview of autoimmune and neoplastic salivary lymphoid proliferations, adapted from Quintana et al.  Benign Borderline LESA (lymphoepithelial sialadenitis), non-clonal (Histological or clonal evidence of neoplasia, but unlikely to disseminate): LESA, clonal; LESA with halos of marginal zone B-cells Low-grade lymphoma Potential for spread to nodes and less often, systemically: low-grade marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) – confluent proliferation of marginal zone B-cells Low-grade marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) with plasmacytic differentiation 5.14.2 Benign Autoimmune Lymphoid Infiltrates the ducts and focally infiltrate the epithelium, unlike in many non-autoimmune chronic inflammatory in- filtrates, where lymphocytic invasion of the ducts is less marked. In LESA many B-cells are of monocyt- oid or marginal zone type . They are slightly larg- er than small lymphocytes of the mantle zone, and are characterised by nuclei with irregular outlines some- what resembling centrocytes . Plasma cells and T- lymphocytes are also present. In time, the ducts con- dense, with partial or complete loss of their lumina, to form lymphoepithelial lesions (LELs) [105, 172, 194]; these were previously inaccurately called epimyoepi- thelial islands and similarly, the old usage of LEL to refer to the whole lesion should be discontinued . LELs consist of cohesive aggregates of epithelium with hyalinised basal lamina material containing variable numbers of B-cells (Fig. 5.55). Myoepithelial cells are present as well, but are often relatively inconspicuous . As the disease progresses the acini become atro- phied and are then totally replaced by lymphoid tissue leading to clinical enlargement of the salivary glands. Monoclonality by PCR can be demonstrated in over 40% of patients with LESA , but this alone is prob- ably insufficient for a diagnosis of lymphoma, and stronger evidence is required from the demonstration of monoclonality by immunohistochemistry or flow cytometry . The most frequent form of autoimmune sialadenitis goes under several synonyms, such as Mikulicz sialadenitis/ disease, myoepithelial sialadenitis (MESA) and benign lymphoepithelial lesion, none of which is satisfactory . In 1999, Harris introduced the much more accu- rate term, lymphoepithelial sialadenitis (LESA) , and this has begun to gain general acceptance, and will be used here. Sjögren’s syndrome is not a pathological term, but a clinical combination of dry eyes and mouth due to autoimmune infiltrates of the lacrimal and salivary glands. It is often associated with other autoimmune or connective tissue diseases, particularly rheumatoid ar- thritis, but also for example scleroderma, systemic lu- pus erythematosus, Hashimoto’s thyroiditis and chronic active hepatitis. Most patients with Sjögren’s syndrome develop LESA, but not so the reverse, as up to 50% of patients with LESA do not develop the clinical features of Sjögren’s syndrome . Lymphoepithelial sialadenitis is considered to be an autoimmune disease [40, 77] of unknown aetiology. Sev- eral viruses have been implicated [76, 88], but they act probably only as cofactors. About 80% of patients with LESA are female, with a mean age at presentation of 55 years (range 1 to 86). The parotids are involved in over 80% of cases (20% bilater- ally), the submandibular glands in 11%, usually in com- bination with the parotids , and other sites in the head and neck in 6% [40, 81]. Tumour-like lesions of the minor glands are rare, but in contrast, subclinical fo- cal periductal and periacinar lymphoplasmacytic infil- trates are frequently seen in the labial salivary glands in Sjögren’s syndrome, and a semi-quantitative assessment of the amount of inflammation in a lip biopsy may be useful as part of the investigation of patients with a dry mouth . In the earliest stages of LESA salivary ducts are di- lated and surrounded by a lymphoid infiltrate with germinal centres. B-cells appear to concentrate around 5.14.3 Malignant Lymphoma ICD-O:9590/3 Overall, extranodal and nodal lymphomas represented 16.3% of all malignant tumours of the major salivary glands at the AFIP from 1985 to 1995 . Almost all extranodal lymphomas are marginal zone B-cell lym- phoma (MALT lymphomas), which is the preferred ter- minology of the current WHO classification of lympho- mas .
164 S. Di Palma · R.H.W. Simpson · A. Skalova · I. Leivo Mucosa-associated lymphoid tissue lymphomas usu- ally present clinically as parotid enlargement, some- times bilateral . There is often a history of Sjögren’s syndrome, but not always. Cases have been reported in post-transplant patients . General lymphadenopa- thy and bone marrow involvement are unusual in MALT lymphoma, and such a presentation favours a diagnosis of nodal lymphoma. The histopathology of MALT lymphoma is inti- mately linked with that of LESA from which it devel- ops – the risk of lymphoma in LESA has been estimat- ed at approximately 4–7% . Histological criteria alone cannot identify exactly when a clonal B-cell pop- ulation emerges in LESA, and in practice the process can be considered not so much a sharp change from one (benign) entity to another (malignant) one, but rather as a spectrum of lymphoma gradually evolving from a purely inflammatory process (Table 5.5) . It can be considered that MALT lymphoma begins as an antigen-driven lymphoid proliferation that pro- gresses first to monoclonality and then, with the ac- quisition of secondary genetic changes, to MALT lym- phoma . The microscopic picture evolves with time ; the earliest morphologically recognisable feature of malig- nancy is the proliferation of marginal zone B-cells to form a distinct halo-like zone around the LELs of LESA. As the lymphoma evolves in a background of LESA mar- ginal zones B cells expand, displace and then replace the follicles. Alternatively, they may colonise the germinal centres assuming a follicular-like architecture (pseudo- follicles) . In addition, there may be foci of sclero- sis, and infiltration by epithelioid histiocytes, which can form small granulomas. Mucosa-associated lymphoid tissue lymphoma re- stricted to the salivary glands is a relatively indolent disease that is often curable with local treatment. 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