S3983 A Rare Case of Malignant Melanoma With Multiple Gastrointestinal Metastases

Introduction: Melanoma is the fifth most common malignancy and poses a significant risk of systemic spread. Melanoma carries a poor prognosis, with a 5-year survival rate estimated at 32% in cases of distant metastasis. Common sites of metastasis include the skin, lungs, gastrointestinal (GI) tract, and central nervous system. In this report, we present a rare case of malignant melanoma with metastases to multiple GI organs, including the gallbladder, small, and large bowel. Case Description/Methods: A 64-year-old woman with history of stage IV malignant melanoma, presented with abdominal pain, constipation, and hematochezia. Surgical history is significant for cholecystectomy of a gallbladder neck mass, confirmed as metastatic melanoma. Computed tomography (CT) abdomen/pelvis demonstrated small bowel intussusception in the mid-abdomen. She underwent colonoscopy which revealed multiple pigmented lesions scattered throughout the right colon and sigmoid/rectum. Biopsies confirmed these lesions as metastatic malignant melanoma. Despite multiple rounds of immunotherapy and radiation, her disease showed significant progression. She later presented with severe abdominal pain, nausea, and vomiting. Repeat CT revealed near-complete obstruction of the sigmoid colon and partial obstruction at the ileum. The obstructions were temporarily relieved with nasogastric tube decompression. However, due to substantial disease burden and refractory to therapy, she decided to transition to hospice care and passed shortly after. Discussion: The GI tract is a common site of metastasis for malignant melanoma, with the small bowel being the most frequently affected location. However, only approximately 4% of patients with GI melanoma are diagnosed prior to death. Patients typically present with nonspecific symptoms such as fatigue, abdominal pain, tenesmus, constipation, diarrhea, melena, and hematochezia. Diagnosis can be achieved through radiographic contrast studies and endoscopic evaluation. This case highlights the critical need for prompt diagnosis in patients who present with GI symptoms and a known history of melanoma. Early detection and intervention could reduce the risk of life-threatening complications and early mortality. It is also important to recognize that disease relapse may occur even after complete surgical resection of metastases in the GI tract. As in this case, her disease continued to spread to small and large intestine post-cholecystectomy. She later developed dysphagia, raising concerns for potential esophageal involvement.