A renal cell carcinoma extending into the renal pelvis simulating transitional cell carcinoma.

A case of renal cell carcinoma with unusual extension is reported, in which the radiographic findings have a close resemblance to those of transitional cell carcinoma of the renal pelvis. We emphasize that it is occasionally difficult to draw a distinction between transitional cell carcinoma with renal invasion and renal cell carcinoma with renal pelvic extension even by computed tomography (CT) and angiography.