BENIGN MYOEPITHELIOMA OF THE SALIVARY-GLANDS - A TRUE ENTITY

Myoepithelioma is a rare neoplasm of the salivary glands which is now recognized as an individual entity in the revised WHO classification. In this study, eleven benign tumours are presented. Most patients gave a history of a slowly enlarging mass, which was cured by surgical exc ision, However, one case recurred several times over 50 years, and ano ther still has residual tumour and removal is not possible. The histol ogical appearances included solid, myxoid and reticular growth pattern s, composed predominantly of spindle shaped or plasmacytoid (hyaline) cells. Many of the tumours also contained occasional small ducts, All 11 tumours were positive for S-100 protein, variable reactions being s een for various other antigens-keratins, human milk fat globulin, carc inoembryonic antigen, alpha smooth muscle actin and vimentin, It is pr obable that myoepithelioma constitutes one end of a biological spectru m which also includes pleomorphic adenoma and some (non-membranous) ba sal cell adenomas, In practice, however, we still advocate retention o f myoepithelioma as a separate diagnostic category, on the grounds tha t it has a range of distinctive microscopic appearances and poses its own unique problems in correct identification.