Primary primitive neuroectodermal tumor of the kidney

Primitive neuroectodermal tumor (PNET) is a small round cell sarcoma that m ainly develops in the central nervous system and soft tissues of childhood; however recently, primary occurrence of this tumor in the kidney has been reported. We experienced one case of PNET primarily arose in the kidney wit hout metastasis. The patient was a 28-year-old man whose chief complaint wa s abdominal pain, especially on exercise. On computed tomography scan and m agnetic resonance imaging, a solid lesion was found in the left kidney, and a left nephrectomy was performed based on the diagnosis of a tumor in the left kidney. The tumor was within the parenchyma of lower end of left kidne y protruding into the abdominal cavity. Histologically, diffuse proliferati on of primitive small round cells with rosette formation was found. Immunoh istochemically, MIC2 gene product, neuron-specific enolase and S-100 protei n were positive. No metastasis to the regional lymph nodes was found. From these observations, the tumor was diagnosed as PNET primarily arising in th e left kidney. Although chromosome analysis was not performed, EWS-FLI1 chi mera gene was identified by reverse transcriptase-polymerase chain reaction on the freshly frozen specimen and fluorescence in situ hybridization on p araffin sections.