S4967 Unmasking a Mucosal Mass in Quiescent Crohn’s Disease: A Rare Diagnostic and Therapeutic Challenges

Introduction: Crohn’s disease (CD) is associated with an increased risk of intestinal metaplasia, particularly in patients with long-standing colonic involvement. However, the development of a mucosal mass after multiple surgeries in a patient with clinically and endoscopic quiescent disease is exceedingly rare. We present a unique case of a large mucosal mass in a CD patient post-definitive surgery and in remission, illustrating the diagnostic complexity and clinical significance of such presentations. Case Description/Methods: A 34-year-old African American man with severe ileocolonic fistulizing CD, refractory perianal disease, and multiple surgeries—including proctocolectomy, abdominoperineal resection with end colostomy, and ileocolonic resection—presented with 4 weeks of fever and 30-lb weight loss. He had failed adalimumab and ustekinumab, and was in clinical and endoscopic remission (Rutgeerts score i2A) on infliximab and azathioprine. Lab work revealed C-reactive protein 241 mg/dL and WBC 22.7 × 10³/µL. He was initially managed for presumed infection with antibiotics. Computed tomography abdomen/pelvis revealed a mass near the ileocolonic anastomosis. Colonoscopy showed a 12 cm fungating, partially obstructing mucosal mass 55 cm from the anal verge, involving two-thirds of the lumen without bleeding. Biopsy revealed atypical epithelioid cells without glandular differentiation, raising suspicion for neoplasia. Differential included histiocytic/dendritic cell neoplasm or epithelial/mesenchymal malignancy. He underwent right hemicolectomy. Pathology showed atypical epithelioid and spindle cell proliferation with inflammatory infiltrate. Outside review favored an inflammatory myofibroblastic tumor, although its mucosal location was highly unusual. The patient recovered uneventfully postoperatively and remained in remission; follow up positron emission tomography scan showed no recurrence. Discussion: This case highlights an uncommon presentation of a large mucosal mass in a CD patient in remission, presenting atypically with fever and systemic inflammation. The diagnostic dilemma of infection vs malignancy underscores the need for vigilance, even in quiescent disease. Neoplastic transformation may occur at anastomotic sites, warranting prompt imaging or endoscopic evaluation in patients with unexpected systemic symptoms despite apparent disease control.