Abstract
Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET) is a childhood malignancy, typically occurring in the bone and rarely in any other part of the body. We herein present a case of ES/PNET of the renal pelvis. A 37-year-old male patient presented with a chief complaint of pain in the left flank and gross hematuria. The tumor had caused moderate hydronephrosis, and ureteroscopic biopsy findings were highly suspicious of sarcoma. Subsequently, radical nephroureterectomy was performed. On the basis of the pathological and cytogenetic findings, a final diagnosis of primary ES/PNET of left renal pelvis was made. Adjuvant chemotherapy with adriamycin and ifosfamide was initiated as ES/PNET often exhibits aggressive biological behavior. The patient was disease-free at his last regular follow-up visit 18 months after the surgery. To our knowledge, this is the first reported case of primary ES/PNET of the renal pelvis.