Carcinosarcoma of the renal pelvis with prominent heterologous elements mimicking teratoma: a case report and literature review

We report a rare case of carcinosarcoma occurred in renal pelvis with prominent heterologous sarcomatous elements mimicking the renal teratoma or adult Wilms’ tumor. A 56-year-old Chinese male patient who presented with right flank pain and gross hematuria was admitted to our hospital. Computed tomography after ultrasound revealed right nephrolithiasis and hydronephrosis. Percutaneous nephrostomy revealed a mass instead of renal stones in the right renal pelvis; therefore, the patient underwent subsequent radical nephrotomy. Histologically, the tumor was composed of the spindle cells, closely packed cells and foci of chondroid and osteoid components within myxoid matrix. The chondroid component showed moderate cellularity and cytological atypia. Calcification and focal osteoid matrix were identified in the periphery of these atypical cartilage islands. Of interest, focal squamous cell carcinoma was also identified in this case. These histological features mimicking the teratoma with somatic cell malignant transformation or adult Wilms’ tumor. However, neither nephrogenic nests nor heterotopic organogenesis was found after the careful observation of the whole slides. Instead, we observed focal squamous metaplasia and severe atypical hyperplasia of the renal pelvic urothelium in one of these slides. Therefore, we rendered a diagnosis of carcinosarcoma of the renal pelvis. The patient suffered from tumor recurrence 2 months after the surgery. The patient refused chemotherapy, and was dead 4 months after the recurrence.