Renal vein leiomyosarcoma. The 11th case of primary leiomyosarcoma of the renal vein is reported. Unique features of this case included concomitant resection of an isolated hepatic metastasis, intraoperative radiation therapy, and the use of electron microscopy and immunohistochemical stains in confirming the diagnosis. A review of the previously reported cases shows a tendency toward slow tumor growth and infrequent recurrence (18%). Metastases are common (82%), primarily to the lung and liver. Aggressive surgical resection and adjuvant radiation therapy, including intraoperative radiation therapy, are recommended. Adjuvant chemotherapy should be considered, although its benefits at present are unclear. 