[Electron microscopic aspects of the histogenesis and diagnosis of undifferentiated skin cancer].

Electron microscopic examination of 29 cases of undifferentiated cancers of the skin was carried out. In group 1 (23 patients) tumors consisted of undifferentiated cells and of those with distinct ultrastructural signs of differentiation characteristic of the epidermis and skin appendages. Tumors of group 2 (6 cases) were formed of undifferentiated cells only. Five histogenetic patterns were identified in group 1. Two patterns included undifferentiated squamous cell carcinomas, while another two--poorly--differentiated adenocarcinomas of sweat and sebaceous glands, and one-tumors of various (mixed) types of differentiation. An ultrastructural classification of undifferentiated skin cancers is suggested which covers all said groups and patterns of skin tumor development.