Small-Bowel Metastatic Melanoma

An 83-year-old man with a history of hypertension, hyperlipidemia, and diverticulosis was hospitalized because of painless hematochezia of 1 day's duration. Two years earlier, he had undergone surgical excision of a superficial spreading melanoma on his right thigh. Eighteen months later, the melanoma recurred, and a wide excision with skin grafting was performed. CT imaging for metastatic disease was negative at that time.

Vital signs were normal, without orthostatic changes. Abdominal findings were benign. Rectal examination revealed scant maroon heme-positive stool. The platelet count, chemistry panel, hepatic profile, and international normalized ratio were normal. After admission, the patient experienced 1 additional bloody bowel movement, his hematocrit fell to 29% from 34.5%, and he required transfusion of 2 units of packed red blood cells.

Colonoscopy revealed blood throughout the colon and in the terminal ileum as well as scattered diverticula. Results of esophagogastroduodenoscopy were unremarkable through the first portion of the duodenum. A CT scan demonstrated only a single suspected polyp within a mid to distal small-bowel loop. However, capsule endoscopy revealed numerous flat pigmented lesions, as well as several ulcerated lesions, throughout the small bowel (A, B, C, and D). Fresh blood in the mid ileum was associated with a large, pigmented, ulcerated mass, presumed to be the site of bleeding (E).

Cutaneous malignant melanoma can metastasize to any organ but shows an unusual predilection for the small bowel.¹ Initially, GI metastases are typically undetectable. The most common methods of identifying small-bowel lesions, contrast-enhanced CT and small-bowel follow-through, have sensitivities of 66% and 58%, respectively.² Capsule endoscopy may improve our ability to detect these lesions and identify surgical candidates.

Treatment of advanced-stage melanoma is controversial; chemotherapy, immunotherapy, and biologic agents do not significantly prolong survival. Currently, the 5-year survival rate is about 5%.³ However, it may be as high as 20% in patients who undergo resection of multiple distant metastases.⁴

References:

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