A mesenteric primary peripheral Ewing's sarcoma/primitive neuroectodermal tumor with molecular cytogenetic analysis: Report of a rare case and review of literature.

Rare cases of Ewing's sarcoma/primitive neuroectodermal tumors (EWS/PNETs) arising from mesenteric tissue have been reported. This report describes an EWS/PNET in a 25-year-old woman who presented with abdominal pain lasting 3 days. Radiologic evaluation revealed a 9 cm × 6 cm homogeneous mass in the lower abdomen with homogeneous enhancement and invasion of the ileum. Surgical resection was completed during exploratory laparotomy. Immunohistochemically, the tumor cells revealed CD99, friend leukemia virus integration-1 and NKX2.2 (NK2 Homeobox 2, a protein coding gene) and subsequently showed EWSR1 rearrangement. The histological feature, immunohistochemical results and genetic fluorescence in situ hybridization analysis of this case were confirming the diagnosis of EWS/PNET. Adjuvant chemotherapy was suggested, but the patient was lost to follow-up.