Inflammatory myofibroblastic tumor of the rectum in a 13-month-old girl: a case report.

Inflammatory myofibroblastic tumor is a rare benign neoplasm. It is common in children and has been reported in various locations throughout the body but rarely in the rectum. A 13-month-old girl presented with a short history of a painless anal mass and no hematochezia. The mass was completely excised, and histologic examination of the initial biopsy showed fascicles of spindle cells in a mixed inflammatory background with predominance of plasma cells, typical of an inflammatory pseudotumor. The spindle cells were positive for smooth muscle actin and anaplastic lymphoma kinase staining. There is no evidence of recurrence or metastasis after a follow-up of 4.5 years.