Extraosseous Ewing sarcoma in the mesentery: the first report of cases in children.

Extraosseous ewing sarcoma (EES) is a rare soft-tissue tumor usually found in the extremities or paraspinal region. We describe the case of a 4-year-old boy with a large cystic mass in the mesentery diagnosed as mesenteric lymphangioma preoperatively and as EES after partial resection and histopathological examination. EES in the mesentery is extremely rare, with only 2 reports described in the English literature. This represents the first report of EES in a child.