[Renal cell carcinoma, primary lesion which was not easily identified: report of two cases]

We report two cases of renal cell carcinoma, primary lesions of which were not diagnosed at an early stage. The first case was a 58-year-old woman, who had nephrectomy due to staghorn calculus of left kidney. Fifteen months later, she died of metastatic cancer whose origin was unknown until the left kidney was re-examined. It was sarcomatoid renal cell carcinoma. The second case was 43-year-old woman, who had amputation of right index finger due to metastatic tumor. Renal cell carcinoma was highly suspected, but no tumor could be found in her kidneys although various urological examinations were performed. Two years later, abdominal CT scan showed a space-occupying lesion (SOL) of left kidney. She had left nephrectomy, and the origin was finally identified.