[Proliferative myositis, a muscular pseudo-sarcoma. Apropos of a case with an ultrastructural study].

A 40-year old woman with a history of rapidly growing tumor of the brachio-radialis muscle is described. By light microscopy, the tumor had typical features of proliferative myositis, with alternating areas of well preserved muscular fibres and strands of proliferating spindle shaped cells and ganglion like cells. Electron microscopic study showed non specific degenerative muscle changes, fibroblasts and giant cells. The histogenesis and the nosologic place of proliferative myositis are discussed.