[Mucoepidermoid tumors of minor salivary glands. Clinical and pathologic correlations. Histoenzymologic and ultrastructural studies (author's transl)].

In a series of 331 minor salivary gland tumors (malignant in about 55,3% of cases), mucoepidermoid tumors, after cystic adenoïd carcinomas, are the most frequent malignant tumors (21,5% of cases). They are much more common in women than in men. The average age of patients at presentation (52,2 years) is higher than that of pleomorphic adenomas. They occur more frequently in buccal floor, tongue and gums. By a half-quantitative study of 71 mucoepidermoid tumors, these neoplasms are ranged in 3 main groups : differentiated epidermoid or glandular tumors, intermediate cell tumors with predominant oncocytic, clear glycogenic or basophilic cells and rare adenosquamous carcinomas. These 3 groups are well demonstrated by histoenzymological investigations, which show high level of oxydative enzymes activity in oncocytic cells and high level of ATPase and alkaline phosphatase activities around basophilic sheets. Besides, an ultrastructural study shows, in addition to well differentiated glandular or epidermoid cells, 3 forms of intermediate cells : young basophilic ribosome-rich cells and more differentiated oncocytic or glycogenic cells. The various structural features of mucoepidermoid tumors are positively correlated with clinical course and behaviour, after long term follow-up studies. Differentiated forms and intermediate clear or oxyphilic cell tumors are of low grade malignancy. Intermediate basophilic cell tumors grow rapidly or metastasize and a lethal course is often noted in these cases.