Aala Dweik, MD, Hadeel Dweik, MD, Maham Shafquat, MBBS, Michel Vulfovich, MD Memorial Healthcare System, Pembroke Pines, FL Introduction: Anorectal melanoma is rare, often diagnosed with advanced disease at presentation. Metastatic spread to the small bowel may result in complications like intussusception. Herein, we report a case of metastatic anorectal melanoma initially presenting as rectal bleeding.
Case Description/
Methods: A 67 year old hispanic female with history of endometrial cancer status post total abdominal hysterectomy and bilateral salpingo-oopherectomy presented to the emergency department (ED) with one day of bright red blood per rectum. Over three months, she had a 20-pound weight loss, constipation, rectal pain, and low appetite. She never had an endoscopy or colonoscopy. She denied prior bleeding, smoking, or alcohol use.
She was febrile (101.2°F) with a BMI of 20.3. Labs showed hemoglobin 8.3, MCV 87.5; other labs were unremarkable. The abdomen was soft, non-tender and non-distended. Rectal exam revealed a large, beefy, tender mass without active bleeding.
Computed tomography (CT) showed an entero-enteric intussusception with a 3.5 x 3.6 cm mass and regional lymphadenopathy. Explorative laparotomy found metastatic melanoma in four small bowel nodules and 9/14 lymph nodes. Hemorrhoidectomy showed malignant melanoma with positive margins. PET showed a hypermetabolic anorectal mass; brain MRI showed three enhancing lesions, largest 2.9 x 1.9 x 2.4 cm in the right temporal lobe with mild mass effect.
She began ipilimumab and nivolumab every 3 weeks x4 cycles, with PET showing decreased anorectal and brain lesions size. Discussion: Melanoma makes up only ~1% of skin cancers, but causes most skin cancer deaths. Adults in the United States (US) have a 2.2% lifetime risk. While global mortality has declined, US rates only modestly improved, likely due to rising cases in high risk groups.
Anorectal melanoma is rare (< 1.2% of melanomas), usually diagnosed in the mid-60's, with slight female predominance. It often presents as rectal bleeding and is frequently misdiagnosed, delaying detection. Metastases commonly involve lymph nodes, lung, and liver; small bowel is less common and later. About 27% of intestinal metastases present with obstruction or intussusception, usually from cutaneous, not mucosal, primaries. These can be life-threatening and need prompt care.
For metastatic anorectal melanoma, the CheckMate 067 trial supports combined immunotherapy with ipilimumab and nivolumab, followed by nivolumab maintenance. This improves survival despite lower response rates in mucosal vs. cutaneous melanoma.
Disclosures: Aala Dweik indicated no relevant financial relationships. Hadeel Dweik indicated no relevant financial relationships. Maham Shafquat indicated no relevant financial relationships. Michel Vulfovich indicated no relevant financial relationships.
Aala Dweik, MD, Hadeel Dweik, MD, Maham Shafquat, MBBS, Michel Vulfovich, MD. P4100 - A Case of Metastatic Melanoma Masquerading as Small Bowel Intussusception, ACG 2025 Annual Scientific Meeting Abstracts. Phoenix, AZ: American College of Gastroenterology.
