Primary malignant fibrous histiocytoma of the endometrium.

Malignant fibrous histiocytoma (MFH) has become one of the most common malignancies occurring in soft tissue. To our knowledge, the present case is the first of MFH occurring in the endometrium. The uterus removed from a 47-year-old woman demonstrated a large multinodular endometrial lesion with gross invasive foci in the myometrium and the left oviduct. Microscopically, the endometrial tumor and the invasive lesions were composed of dense sheets of markedly pleomorphic cells consisting of fibroblast-like cells, histiocyte-like cells, foamy histiocytes, benign appearing multinucleated giant cells resembling either osteoclasts or Touton giant cells, and bizarre tumor giant cells. Some of the tumor cells showed phagocytic activities. The tumor cells were oriented in a random or haphazard fashion and classical storiform and fascicular patterns were not observed. The tumor was diagnosed as MFH consisting exclusively of so-called pleomorphic pattern. The patient is alive without evidence of disease, months following total hysterectomy and bilateral salpingo-oophorectomy.