[A case of renal pelvic tumor with heterotopic bone formation].

The patient was a 74-year-old man who was referred to our hospital with a complaint of left flank pain. Laboratory data were almost within normal limits and urine cytology was positive. X-ray examination revealed a calcification in the left kidney and abdominal CT scan confirmed the presence of a heterogenous renal pelvic mass which contained a calcification. Based on these examinations, a diagnosis of a renal pelvic cancer with heterotopic bone formation was made. Subsequently, left nephroureterectomy was performed. Grossly, the renal pelvis of the resected kidney was filled with a mass which had a white cut surface and bone-like tendency. Histopathologically, a poorly differentiated transitional cell carcinoma with massive bone formation was found. Fifty five cases of heterotopic bone formation in the kidney have been reported in Japan. Among the cases, 4 cases were complicated with renal pelvic tumor and our case was the second case of heterotopic bone formation complicated with a transitional cell carcinoma of the renal pelvis in Japan.