Inflammatory myofibroblastic tumor of the abdominal wall simulating rhabdomyosarcoma: report of a case.

We report the case of a 6-year-old boy with a progressively enlarging mass in the anterior abdominal wall. Computed tomography showed an intensely enhancing heterogeneous lesion arising from the anterior abdominal wall muscles with intraperitoneal extension. Based on the location of the tumor and the radiological findings we made a provisional diagnosis of rhabdomyosarcoma. However, the findings of fine-needle aspiration and Trucut biopsy were inconclusive for malignancy. We performed complete excision of the mass, including the involved left costal segment. Microscopically, the tumor was composed mainly of spindle-shaped cells without malignant features, and immunohistochemical analysis revealed positive staining for actin. These findings confirmed a diagnosis of an inflammatory myofibroblastic tumor (IMT). To our knowledge, this is the first case report of an extrapulmonary IMT arising from the anterior abdominal wall.