Primary Ewing's sarcoma/primitive neuroectodermal tumor of the kidney that responded to low-dose chemotherapy with ifosfamide, etoposide, and doxorubicin.

A primitive neuroectodermal tumor (PNET) is a small round cell tumor that arises from the nerve crest. This tumor usually occurs in the central nervous system or soft tissue, but it can occur in the kidney in rare cases. Herein we report a case with severe multiple liver metastases after surgery for right renal PNET. The patient was a 21-year-old man with a chief complaint of right abdominal pain. Hemorrhage in a right renal malignant tumor was diagnosed, and radical nephrectomy was performed. Histopathology showed bare nuclear round atypical cells with a scarce cytoplasm proliferating like a seat and nest. Some of the cells formed a rosette structure and the tumor cells were positive for CD99, leading to diagnosis of PNET. Severe multiple liver metastases occurred 6 months after surgery, and six courses of chemotherapy with ifosfamide, etoposide and doxorubicin were performed. After this treatment, residual tumor was removed, but the tumor cells were absent histologically.