Pathology of the Head and Neck

138 S. Di Palma · R.H.W. Simpson · A. Skalova · I. LeivoTable 5.1. Revised WHO histological classification of salivary gland tumours [171]5AdenomaDuctal papillomaCystadenomaCarcinomasNon-epithelial tumoursMalignant lymphomasSecondary tumoursUnclassified tumoursEntities not included in the classification,but described or better characterised since1991 [8a]Pleomorphic adenomaMyoepithelioma (myoepithelial adenoma)Basal cell adenomaWarthin’s tumour (adenolymphoma)Oncocytoma (oncocytic adenoma)Canalicular adenomaSebaceous adenomaInverted ductal papillomaIntraductal papillomaSialadenoma papilliferumPapillary cystadenomaMucinous cystadenomaAcinic cell carcinomaMucoepidermoid carcinomaAdenoid cystic carcinomaPolymorphous low-grade adenocarcinoma (terminal duct adenocarcinoma)Epithelial-myoepithelial carcinomaBasal cell adenocarcinomaSebaceous carcinomaPapillary cystadenocarcinomaMucinous adenocarcinomaOncocytic carcinomaSalivary duct carcinomaAdenocarcinoma (not otherwise specified)Malignant myoepithelioma (myoepithelial carcinoma)Carcinoma in pleomorphic adenomaSquamous cell carcinomaSmall cell carcinomaUndifferentiated carcinomaOther carcinomasSialoblastomaHyalinising clear cell carcinomaCribriform adenocarcinoma of the tongueEndodermal sinus tumour of the salivary glandslium-lined spaces. As in benign myoepithelioma (seeSect. 5.8.2), neoplastic myoepithelial cells may take severalforms – epithelioid, spindle, plasmacytoid, clear andoncocytic, as well as transitional forms with features oftwo or more of these types (Fig. 5.9).The stroma varies in amount and is either dense eosinophilichyaline material or chondromyxoid tissue.The former is composed of basement membrane materialand stains with PAS diastase and collagen type IV;the chondromyxoid material only rarely resembles truecartilage and is Alcian blue-positive (Fig. 5.10). Calcificationand bone formation can occur in long standingtumours. Occasionally, collagenous spherules and crystalloidsare seen, particularly in tumours rich in myoepithelialcells of the plasmacytoid type (Fig. 5.11) [197].Nuclear atypia is not common, but can be seen in tumourswhere epithelial or myoepithelial cells display oncocyticfeatures [65]. Occasional myoepithelial cell nucleiare enlarged and bizarre, somewhat analogous to“ancient” change in schwannomas. Mitotic figures aregenerally sparse, but can occur as part of the repair processafter FNA. Such tumours with these atypical featuresshould be sampled thoroughly to exclude true intracapsularcarcinoma.Similarly, areas of necrosis or haemorrhage may followsurgical manipulation, FNA or other trauma, and