A Case of Extraskeletal Ewing's Sarcoma Arising from Duodenum.

Extraskeletal Ewing's sarcomas (EES) are rare. Recently, Ewing's sarcoma of the bone, primitive neuroectodermal tumor (PNET), Askin tumor and EES have been included into the family of Ewing's tumors, due to the overlapping features relating to their clinico-pathological and cytogenetic appearance. We experienced a case of an EES arising from the duodenum in a 14-year-old girl who presented with hematemesis and epigastric discomfort. A duodenal biopsy specimen revealed the infiltration of small round cells and rich vasculatures, with immunohistochemical finding of MIC-2 (CD99) (+), vimentin (+), CD56 (NCAM) (+), LCA (-), T-cell (-), B-cell (-), CD43 (-) and CD68 (-). She was treated with several cycles of multiagent chemotherapy, and achieved an initial partial response, but rapid progression of tumor followed, so she was treated with surgical excision. This is the first case report of an EES arising from the duodenum in the literature.