Primitive neuroectodermal tumor of the kidney.

We report a 21-year-old man with a primitive neuroectodermal tumor (PNET) of the kidney that was difficult to distinguish from other small round cell tumors, e.g., small cell carcinoma, malignant lymphoma, and Wilms' tumor. Pathologically, a primitive rosette-like pattern was shown by H&E staining; expression of MIC-2 was indicated by an immunohistochemical test; rather primitive organelles were observed by an ultrastructural method; and translocation of chromosome 22 was confirmed by FISH. We therefore diagnosed the current case as PNET. The patient had undergone a right radical nephrectomy more than 1.5 years earlier. After neither metastases nor recurrences for 0.5 year, imaging examinations revealed masses in his liver. He received chemotherapy and underwent surgery again, but the masses were not composed of viable tumor cells. PNET of the kidney is extremely rare; fewer than 30 cases have been reported in the English literature, and there are few data on the expression of p53, ki67, and bcl2. We investigated the relationships between these markers in the current case using immunohistochemical tests and observed strong expression of p53, Ki-67, and bcl-2. Such results generally indicate poor prognosis, and the patient eventually had some masses in his liver, but no viable tumor cells were found. The prognostic significance of these various markers in PNET of the kidney still remains unclear, but p53, ki-67, and bcl-2 might not be so important as indicators of prognosis in the kidneys as they are in other organs. Further studies are needed to investigate this, and we hope that the patient recovers completely.