HISTOLOGY OF MUCOEPIDERMOID CARCINOMAS - ANALYSIS OF 327 CASES

The mucoepidermoid carcinomas of the salivary glands (MEC) show histol ogically a wide spectrum of differentiation from solid epidermoid tumo urs to cystic mucous-filled tumours. Epidermoid cells, mucous cells an d intermediate cells are the main cellular components. Besides clear c ell (I 1.0%) and oncocytic (0.6%) variants and ''cystic'' (25.4%) tumo urs can be observed. According to the per cent of mucous cells and cys tic spaces of the total tumour mass different degrees of histomorpholo gic differentiation can be distinguished. Therefore highly differentia ted MEC (53.2%) with more than 50% mucous cells and cystic spaces, res pectively low-differentiated MEC (46.8%) showing less than 50% mucous cells and cystic spaces can be subclassified. In respect of the therap eutic proceeding it should be recognized that the histopathological su bclassification of MEC of the salivary glands (7) is based on morpholo gical criteria only. It may not be equalised with a grading of maligna ncy since even highly differentiated MEC can grow infiltratively, some times osseo-destructively, to recur locally and to metastasize predomi nantly into the regional lymph nodes. Consequently the histopathologic al subclassification of MEC does not allow certain prognosis in indivi dual cases.