[The limit in differential diagnosis of renal angiomyolipoma from renal cell carcinoma on computerized tomography: a case report].

Recent reports have described that the accurate preoperative diagnosis of renal angiomyolipoma is possible with computerized tomography (CT). There are, however, some cases of angiomyolipoma which are indistinguishable from renal cell carcinoma on CT. Herein we report a case of renal angiomyolipoma which CT failed to reveal preoperatively. In a 71-year-old Japanese male, a left renal tumor was incidentally suspected on excretory urogram. Then CT demonstrated a homogeneous mass in the upper part of the left kidney, 6 cm in diameter, which showed a positive attenuation coefficient, slightly denser than renal parenchyma. Selective left renal arteriogram showed hypervascularity without aneurysmal formation or arteriovenous fistula. These radiologic findings strongly suggested renal cell carcinoma and radical left nephrectomy was performed. Histological examination confirmed angiomyolipoma composed mainly of smooth muscle with thick-walled vessels and immature fat cells. We reviewed the literature and discussed the computerized tomographic-pathologic correlation of angiomyolipoma.