S6047 Lead Point Deception: Metastatic Melanoma-Induced Intussusception Disguised as Terminal Ileal Obstruction

Introduction: Metastatic melanoma to the small bowel is uncommon and often underdiagnosed in clinical practice, with antemortem recognition in only 2–5% of advanced melanoma cases. Such metastases can cause nonspecific gastrointestinal symptoms or complications like obstruction and intussusception. We present a diagnostically challenging case of multifocal small bowel melanoma initially presumed to be a solitary terminal ileal lesion. Case Description/Methods: A 75-year-old man with a history of nodular melanoma (Breslow depth 3.35 mm) was treated in 2021 with wide local excision and sentinel lymph node biopsy. He subsequently presented in July 2024 with hemoptysis. Imaging showed multiple pulmonary nodules, and robotic bronchoscopy confirmed metastatic melanoma. Positron emission tomography (PET)/computed tomography demonstrated widespread metastatic disease involving the skin, lungs, bones, and mesenteric lymph nodes, however, no clear enteric lesions. Immunotherapy with nivolumab, relatlimab, and palliative radiation to bone lesions resulted in partial disease regression. In February 2025, the patient developed abdominal bloating, anemia, and heme-positive stools. Colonoscopy revealed a pigmented, ulcerated lesion intermittently prolapsing through the ileocecal valve, thereby raising suspicion for a “ball-valving” terminal ileal melanoma causing intermittent small bowel obstruction. Due to escalating obstructive symptoms, he was referred for surgical management. Intraoperatively, multiple jejunal and ileal intussusceptions were identified, each with intraluminal masses acting as lead points. He underwent robotic right hemicolectomy and segmental small bowel resection. Pathology revealed multifocal metastatic melanoma involving both the jejunum and ileum. The patient had an uncomplicated postoperative recovery and resumed immunotherapy within 1 month. Discussion: This case highlights the diagnostic challenges in identifying small bowel melanoma. While colonoscopy suggested a solitary obstructing lesion, surgical findings revealed multifocal disease not visible on PET/computed tomography, which showed only mesenteric lymphadenopathy. Clinicians should maintain high suspicion for multifocal involvement in melanoma patients with vague gastrointestinal symptoms, as imaging and endoscopy may underestimate disease extent. Surgical exploration may be essential for both diagnosis and symptom relief.