[A case report of angiomyolipoma arising from the renal capsule]

A case of angiomyolipoma arising from the renal capsule is reported. A 49-year-old female was admitted to our hospital with a complaint of abdominal mass pointed out by ultrasonography during her yearly health check. The tumor was 10 cm in size. On abdominal enhanced CT, the tumor was existed behind the left kidney. The capsule of the tumor was enhanced and the septums were seen inside of the tumor. MRI revealed a hemorrhage in the tumor and selective renal angiography showed the tumor was fed by the renal capsular artery. A tumor of the renal capsule was suspected and a laparotomy was done. Pathological results by the frozen section suggested malignancy and radical nephrectomy was performed. Angiomyolipoma was diagnosed histologically. Tumors of the renal capsule are uncommon and angiomyolipoma of the renal capsule is extremely rare. We have found only two cases in Japanese medical literature.