EWS FLI-1 FUSION TRANSCRIPTS IN 3 PERIPHERAL PRIMITIVE NEUROECTODERMAL TUMORS OF THE KIDNEY/

Although primitive neuroectodermal tumor (PNET) is a well-recognized e ntity, its renal localization as a primary site has not been appreciat ed. Only nine cases of renal PNET exist in the literature. The paucity of renal PNET could be explained by the lack of objective diagnostic techniques that would facilitate its distinction from other primitive round cell tumors of the kidney, such as the more widely recognized mo nophasic Wilms' tumor and clear-cell sarcoma of the kidney (CCSK), as well as renal carcinoid, or neuroblastoma invading the kidney from the adjacent adrenal gland. The recently identified specific fusion trans cripts detectable by reverse transcription polymerase chain reaction ( RT-PCR) have provided us with a valuable tool for the detection of ren al PNET. This article reports three renal PNET that expressed EWS/FLI- 1 fusion transcripts by RT-PCR, in addition to positive staining for M IC2 protein and neuron-specific enolase (NSE). One also exhibited dens e core granules in cell processes by electron microscopy. Employment o f such methodology will lead to a more accurate classification of rena l tumors.