Detection of fat in a renal cell carcinoma mimicking angiomyolipoma

The authors report a case of renal cell carcinoma in which computed tomography (CT) revealed fatty tissue and calcification within a solid renal mass. The detection of a mass with negative CT numbers at CT and increased echogenicity at ultrasound led to the incorrect diagnosis of angiomyolipoma (renal hamartoma). The presence of intratumoral calcification should have prompted further evaluation because angiomyolipomas usually do not calcify. The authors do not believe that the nonsurgical approach to angiomyolipomas should be abandoned.