An unusual presentation of abdominopelvic inflammatory myofibroblastic tumor in an adolescent male: a rare case report

Introduction: Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm with intermediate malignant potential, most commonly affecting the lungs and the abdominal and pelvic soft tissues. Pediatric abdominopelvic IMTs are exceptionally rare and often mimic malignant tumors. Case presentation: A 14-year-old Iranian male presented with 3 weeks of fever, abdominal and pelvic pain, nausea, constipation, and weight loss. Physical examination revealed a firm hypogastric mass. Laboratory tests showed elevated inflammatory markers but normal tumor markers (carcinoembryonic antigen, carbohydrate antigen 19-9, and alpha-fetoprotein). Imaging demonstrated a lobulated abdominopelvic mass between the bladder and rectum with internal necrosis and mild ascites. The patient underwent midline laparotomy under general anesthesia at a pediatric surgery center, during which a 10 × 8 cm firm mass adherent to the omentum was excised entirely with minimal blood loss (≈20 mL). Histopathology revealed a spindle-cell lesion with storiform architecture, chronic inflammatory infiltrate, focal necrosis, and microscopic adipose invasion, consistent with IMT. The postoperative course was uneventful, and the patient remained asymptomatic with no recurrence at a 6-month follow-up. Clinical discussion: Abdominopelvic IMTs are diagnostically challenging due to nonspecific presentation and imaging overlap with malignancy. Complete surgical excision is the treatment of choice, and long-term surveillance is essential due to the risk of recurrence, particularly in large or epithelioid variants. Conclusion: This report describes an unusual abdominopelvic IMT in an adolescent male and emphasizes the importance of considering IMT in the differential diagnosis of pediatric abdominopelvic masses.