Leiomyosarcoma of the uterus with focal rhabdomyosarcomatous differentiation.

An unusual myometrial tumor was encountered in a 70-year-old female who presented with lower abdominal fullness and symptoms related to pulmonary metastases. Laparotomy revealed a uterine mass that was removed by total abdominal hysterectomy and bilateral salpingo-oophorectomy. Multiple liver metastases also were noted. Pathologic examination of the hysterectomy specimen revealed a 25-cm, well-circumscribed myometrial mass that had a firm, white-to-yellow, focally whorled, sectioned surface with focal hemorrhage and necrosis. Within the main mass was a discrete, 7-cm, soft, gelatinous, reddish-yellow nodule. The main tumor was a well-to-moderately differentiated leiomyosarcoma, whereas the gelatinous nodule was rhabdomyosarcomatous and contained rhabdomyoblasts that exhibited cytoplasmic cross striations and immunoreactivity for myoglobin. No epithelial elements were detected in the neoplasm. At the time of last follow-up, the patient was undergoing chemotherapy. This is only the second well-documented case of a hybrid leiomyosarcoma-rhabdomyosarcoma of the uterus.