[Ultrastructural study of fibrosarcoma].

Ultrastructure of 9 cases of fibrosarcoma was observed and compared with that of fibrous connective tissue of 4 human embryos and 9 cases of spindle cell sarcoma, including 3 each of leiomyosarcoma, neurofibrosarcoma and dermatofibrosarcoma protuberans. Ultrastructurally, fibrosarcoma consisted of well-differentiated fibroblast-like cells, poorly differentiated fibroblast-like cells (embryonic fibroblast-like cells), myofibroblast-like cells and primitive mesenchymal cells. It is suggested that fibrosarcoma may arise from primitive mesenchymal cells which are capable of differentiating into fibroblast and myofibroblast. There were two special cases of fibrosarcoma in this series. One was a congenital fibrosarcoma with ultrastructure resembling adult and the other was a sarcoma of myofibroblast. Diagnosis and differential diagnosis between fibrosarcoma and leiomyosarcoma, neurofibrosarcoma, dermatofibrosarcoma protuberans are discussed.