Molecular genetic analysis of a small bowel primitive neuroectodermal tumor.

We present a pediatric peripheral primitive neuroectodermal tumor (pPNET) localized exclusively to the small bowel. The tumor presented in an adolescent male and the diagnosis was confirmed by electron microscopy, CD99 immunopositivity, and molecular genetic analysis that demonstrated an EWS-FLI1 type 2 fusion transcript. This case report and a review of the literature underscore the considerable phenotypic overlap in EWS-related tumors in this site and the necessity for molecular genetic analysis to permit accurate classification.