Introduction : Primitive neuroectodermal tumor (PNET) is an extremely rare small round cell tumor that  usually present  in the central nervous system, bone or soft tissue, but it can occur in the kidney in rare cases.

 Materials and Methods : We described the clinicopathologic features of 10 cases of renal PNET with its differential diagnosis and immunohistochemistry including CD99, cytokeratin, desmin, NSE, Vimentin and LCA. 

Results : The patients (7 men, 3 women) ranged from 3 to 56 years of age ( average 20yrs). The  tumor size was ranged from 14 to 25cm. Presenting symptoms included abdominal/flank pain, lumber lump, hematuria, fever off and on, weakness and loss of appetite. Immunohistochemical results on the renal PNET were positive for CD99 mostly and Vimentin in some. Tumor  cells  showed a rosette forming structure and positive for CD99, leading to diagnosis of PNET.  

Conclusion: Renal PNETs are veru unusual tumor characterized by aggressive behavior with local recurrence potential and distant  metastasis, which causes poor prognosis.