Malignant fibrous histiocytoma of the uterus. Some immunohistochemical and ultrastructural observations.

Hysterectomy was performed in a 64-year-old woman because of a uterine malignant tumor which extensively involved both the endometrium and the myometrium. Histological examination revealed a malignant fibrous histiocytoma (MFH) of the pleomorphic-storiform type. The presence of epithelial or heterologous mesenchymal tumor components or cells of smooth muscle derivation was ruled out by immunohistochemistry and electron microscopy. The patient developed pulmonary metastases and died six months after surgery. MFH is a rare primary tumor of the uterus, but it should be considered in cases of malignant mesenchymal tumors without heterologous elements or signs of smooth muscle derivation.