Abstract

Electron microscopic study of two malignant fibrous histiocytomas confirmed the presence of previously described tumor cells in the literature. In addition, there existed intermediate cells with morphologic features of both myofibroblasts and histiocytes, or both histiocytes and smooth muscle cells. Our result supported the idea that malignant fibrous histiocytoma may be derived from the undifferentiated mesenchymal cells that differentiate primarily along a fibroblastic and histiocytic cells.