Ewing sarcoma/primitive neuroectodermal tumor of the kidney: a case report. Diagnosed by immunohistochemistry and molecular analysis.

Background: Ewing sarcoma/primitive neuroectodermal tumor (EWS/PNET) of the kidney is a rare and aggressive tumor. It has a rapid clinical progression with early metastasis and death. Few cases with documented t(11;22) have been reported in the literature.

Case Presentation: We report a case of EWS/PNET of the kidney in a 26-year-old woman with widespread metastasis at initial presentation. The tumor cells showed strong expression for CD99 and FLI-1 monoclonal antibodies and polyclonal antibodies and were negative for WT1 and numerous other markers. The diagnosis was subsequently confirmed by demonstrating t(11;22)(q24;q12) using cytogenetic karyotyping and fluorescence in situ hybridization.

Conclusions: Due to the different prognosis and management between EWS/PNET and other primary renal neoplasms with similar morphology, a histopathologic diagnosis with extreme accuracy should be made. Cytogenetic analysis is an important supportive tool to immunohistochemistry in making the final diagnosis.