Mesenteric leiomyosarcoma in a 13-year-old boy.

Mesenteric leiomyosarcoma occurs most commonly in middle-aged individuals. Primary tumors of the mesentery are uncommon in pediatric and adolescent patients, and primary mesenteric leiomyosarcoma is particularly rare. Accurate preoperative diagnosis of mesenteric soft tumor is generally difficult. We describe a case of leiomyosarcoma arising from the ileal mesentery in a 13-year-old boy. The diagnosis was based on histopathologic evaluation using immunohistochemical staining and gene analysis.