唾液腺多形性腺腫の組織発生をめぐる問題点

抄録

An electronmicroscopical study was performed to analyse the current controversy upon the histogenesis of the pleomorphic adenoma of the salivary gland. Morphological characteristics of the pleomorphic adenoma of the parotid gland were studied and were compared with those of the embryonal ductal and myoepithelial cells of the human parotid glands and also with those of the cultured cells of the normal human parotid glands, Morphology of the tumor cells constituting the pleomorphic adenoma is characterized by its diversity but ultrastructurally apparent transition from the tumor cells similar to the typical peripheral duct cells into the chondroid cells are observed. Histogenetically the peripheral duct cell plays the dominant roles in this tumor. But judging from the morphological characteristics of the tumor cells and also from the histoarchitecture of the tumor, the myoepithelial cells are also involved in tumorigenesis. Tumorigenesis from the reserve cells which preserve multipotentiality to develop into the ductal cells and also into the myoepithelial cells may explain these inconsistency. During early developmental stage of the embryonal parotid gland, primitive intralobular duct cells are regularly doubly layered. These cells located in the basal layer are confirmed ultrastructurally to develop into the myoepithelium in the later stage, but it is also assumed possible that these cells are basal cells whhich have a potentialty to developed into the ductal cells simultaneously. By tissue culture of the human parotid gland outgrowth of cells which have morphological characteristics of ductal epithelium are observed. The cytoplasm of most of these cells are characterized by abundant presence of the various filamentous structure. This shows thatenvironmental change can easily influence upon formation of the filamentous structures in the cytoplasm of these cells. The filamentous structures which are commonly observed in the tumor cells of the pleomorphic adenoma are difficult to be definitely discriminated morphologically, whether myofilaments or tonofilaments.