Primary primitive neuroectodermal tumor of kidney: a rare case report with diagnostic challenge.

Primary primitive neuroectodermal tumors (PNETs) of the kidney are quite rare and can be mistaken for a wide variety of other small round blue cell tumors which includes rhabdomyosarcoma, Wilm's tumor, carcinoid, neuroblastoma, clear cell sarcoma of the kidney, lymphoma etc. Renal Ewings/PNET can occur in the age group from 4 to 61 years. Approximately, 90% of Ewing sarcoma (ES)/PNET have a specific t(11;22) which results in a chimeric EWS-FLI-1 fusion protein. Immunohistochemical for the carboxy-terminus of FLI-1 is sensitive and highly specific for the diagnosis of ES/PNET. Herein, we have an interesting presentation in a 23-year-old male who came with neck pain and progressive quadriparesis and was diagnosed as a case of poorly differentiated malignant tumor with a differential of lymphoma versus metastatic renal cell carcinoma. The patient's condition deteriorated fast and he had a rapid downhill course. The final diagnosis of Ewings/PNET was confirmed at autopsy.