Intra-abdominal polyphenotypic tumor.

The presence of t(11;22)(q24;q12) is often considered diagnostic of Ewing sarcoma and peripheral primitive neuroectodermal tumor (pPNET). We report a case of a polyphenotypic tumor that possessed this translocation as detected by reverse transcriptase polymerase chain reaction (RT-PCR). This tumor was positive for vimentin, desmin, low-molecular-weight keratin, neuron-specific enolase, S-100 protein, and CD57 by immunohistochemistry. Of note, the tumor was negative for MIC2. The tumor had double-minute chromosomes with > 100 copies of the MDM2 gene. Thus, the presence of the t(11;22)(q24;q12) translocation should not be considered diagnostic of Ewing sarcoma and pPNET in the absence of supporting histologic evidence such as positive staining for MIC2. The presence of this translocation in Ewing sarcoma and pPNET has been taken as evidence that these two tumors are related. Rather than extending this relationship to include some polyphenotypic tumors, other tumors may acquire this genetic change during tumor progression. Treatment regimens for tumors may be better based on phenotype rather than genotype when these two profiles are seemingly in conflict.