Primary renal angiosarcoma: a case report and review of the literature.

Primary renal angiosarcoma is very rare. To our knowledge, only 15 cases have been reported to date. A 77-year-old Japanese man with a unilateral kidney presented with massive hematuria followed by renal failure. A renal tumor was suspected and a left nephrectomy was performed. The histopathological diagnosis was angiosarcoma of the kidney. A hemorrhagic tumor measuring 10 x 5 cm and clotted blood was found in the medullary area. The atypical tumor cells had a sinusoidal and solid appearance, and showed immunohistochemically positive reactions for some of the endothelial markers. The patient died about 21 months after the nephrectomy and the autopsy revealed massive metastases to the liver and retroperitoneum. One of the differential diagnoses of the case was angiomyolipoma, because the tumor cells were relatively bland in their histological appearance with entrapped fat cells in the pelvic area. Fifteen case reports with titles that included the term 'hemangiosarcoma/angiosarcoma', 'hemangioendothelioma/endothelioma' or 'vascular sarcoma' of the kidney were reviewed and compared to the present case.