Primary primitive neuroectodermal tumor of the kidney: a case report.

There are nearly 50 PNET cases in the literature with primary renal localization. The mean age for renal PNET is 28 but it can be seen in a wide range between 4 and 69 years. In this atypical localization PNET may be mistaken with a variety of small round cell tumors, particularly with blastema predominant Wilms' tumor and due to its distinctive prognostic and therapeutic features differential diagnosis is very important. Immunohistochemical studies are useful in discriminating PNET from other renal small round cell tumors. Renal PNETs tend to metastasize at early stages and they have a high rate of recurrence. Our case is a 45-year-old male presented with left flank pain and hematuria. In computerized tomography a mass in left kidney was observed and nephrectomy was performed. Histopathologic examination revealed a small round cell tumor with rosettes and pseudorosettes. Immunohistochemically the lesion was diffuse strong positive with CD99 and NSE, negative with LCA, pancytokeratin, vimentin, desmin, smooth muscle actin, chromogranine A and S-100. At the time of diagnosis the pathologic stage of the tumor was T1aN0Mx. The patient did not take any further therapy and in 1-year follow-up no local recurrence or distant metastasize occurred.