[Salivary gland myoepithelioma. Histological, histoenzymological and ultrastructural study]

One case of myoepithelioma of the submandibular gland is reported. The tumor was composed of mixed spindle-shaped and plasmacytoid cells. The electron microscopy showed intracytoplasmic myofilaments, with variations in number and in repartition from one cell to another. Histoenzymologically, ATPasic and alkaline phosphatase activities could not be demonstrated in these poor differentiated myoid cells. Usually, the tumor has a good behavior. It represents a rare tumor (7 cases - 0,8% - in a retrospective study of 850 salivary gland tumors). Without demonstration of myofilaments by ultrastructural analysis, the diagnosis of such a tumor is very difficult. Taking into consideration new concepts about the myoepithelial cell, the histogenesis of this neoplasm is discussed.