[Histogenesis of storiform tumors (an electron microscopy study)]

The question of histogenetic relations between storiform tumours led to electron-optic revision of 29 skin histiocytomas, 10 sclerosing hemangiomas, 13 lenticular dermatofibromas and 10 protuberant dermatofibrosarcomas. Endothelia and pericytes with numerous transient formations, together with various degrees of lipid or some other accumulation on the one hand and fibroproduction tied up with the lateral membrane on the other, were found in all in varying degrees. The filamentous component of tumorous cells had always the properties of myofibrils with a tendency to brushlike formations dependent on the cellular membrane which usually contained numerous pinocytotic vacuoles. It thus differed from the cells of storiform neurofibromas (4 cases), whose intracytoplasmatic filaments showed no tendency to clustering or relation to the cellular membrane. Moreover, in their finer lateral membrane no substantial production of collagenous fibers occurred. According to the results of the study, histiocytoma, sclerosing hemangioma and dermatofibroma belong to the same category of tumours from mixed vasoforming tissue. Of the same, but mostly hemangiopericytary, origin is probably also protuberant dermatofibrosarcoma provided it is histogenetically uniform. Storiform neurofibroma is structurally different.