P1.009: Colonic Conundrum: An Unusual Presentation of Inflammatory Myofibroblastic Tumor in the Ascending Colon

Introduction: Inflammatory myofibroblastic tumor (IMT) is a rare benign tumor that typically occurs in the lungs, although it can develop in other sites such as the abdomen, pelvis, and gastrointestinal tract (GI). Within the GI tract, colonic involvement is particularly rare and poses a diagnostic challenge due to its nonspecific clinical presentation, which can mimic more common conditions such as inflammatory bowel disease, infectious colitis, or gastrointestinal malignancies. We present a case of a 7-year-old boy who presented with abdominal pain, hematochezia, and anemia and was subsequently found to have IMT in the ascending colon.

Case Description: A 7-year-old male with a history of chronic constipation, treated with polyethylene glycol 3350, presented with a 2-month history of worsening periumbilical abdominal pain, particularly postprandial. His symptoms worsened three days before admission, with melena and a decreased appetite. Laboratory workup showed anemia (Hemoglobin 6.6 g/dL, Hematocrit 22.8%), a markedly elevated CRP (5.3 mg/dL), and a positive fecal occult blood test. Iron studies confirmed iron deficiency anemia (ferritin 3 ng/mL, transferrin saturation 2%, iron 10 µg/dL, ret Hb 20pg). Despite initial negative findings on a Meckel scan and an unremarkable esophagogastroduodenoscopy, a colonoscopy revealed a right colonic intussusception with a 4 cm mass serving as the lead point (Figure 1).
Imaging via abdominal ultrasound confirmed the classic "target sign" of intussusception, with calcifications (Figure 2). Attempts at non-operative reduction via contrast enema were unsuccessful, necessitating surgical intervention. A diagnostic laparoscopy revealed a mass that warranted resection, culminating in a right hemicolectomy. Pathology indicated IMT with spindle cell proliferation and dense lymphoplasmocytic infiltrate, confirmed by positive Vimentin and negative CD31, EMA, ALK1, SMA, Desmin, CD34, and HMB45. Fluorescence in situ hybridization for ALK gene rearrangement was normal. His postoperative recovery was uneventful, marking the resolution of an elusive yet formidable diagnostic challenge.

Discussion: IMT is a rare mesenchymal tumor, primarily affecting children and young adults. While typically found in organs like the lungs and liver, colorectal involvement, particularly in the ascending colon, is uncommon. Upper GI bleeds in pediatrics have various differentials, and non-GI causes, such as IMTs, should be considered, as they can mimic intussusception symptoms. Contrast-enhanced CT is the preferred diagnostic tool, showing a hypodense, well-defined mass, with a definitive diagnosis requiring histopathological examination. Surgical resection is the primary treatment, with recurrence possible, necessitating long-term follow-up. In our case, follow-ups every six months showed no signs of recurrence.

Conclusion: This case serves as an excellent example supporting the idea that intussusception in school-age children is often caused by a pathological lead point and typically requires surgical management for resolution. It also highlights the need for further research into the incidence and management of GI IMT in the pediatric population.