The occurrence of rectosigmoid junction inflammatory myofibroblastic tumor (IMT) is uncommon in children. This is a rare form of mesenchymal tumor, belonging to the category of soft tissue tumors, and can be found at any anatomical site from the central nervous system to the gastrointestinal tract.

Our patient was a 10-year-old male subject complaining of lack of defecation and constipation. The patient had decreased the frequency of defecation and constipation about two weeks before his referral and had not improved despite the use of laxatives. The abdomen was completely distended and there was no tenderness or guarding in the examination. Several airfluid levels are shown on the abdominal X-ray. In the ultrasound, free fluid was reported in the interlobular and pelvic spaces. The patient was transferred into the operating room. A tumor of the rectosigmoid junction was detected. Histopathologic studies showed evidence of IMT.

IMT is a rare neoplasm of unknown origin, which may occur in various sites of the body. Complete surgical removal is usually curative, but early detection of recurrence is required. Treatment options include chemotherapy, radiation therapy, and immunotherapy. Further investigations are needed to improve the understanding and management of this rare tumor.