Metastatic Malignant Melanoma, Could it Hide a Primary Gut Culprit?

Abstract

Background: Malignant Melanoma is one of the most common tumors to metastasize to the gastrointestinal (GI) tract from cutaneous primary source. Primary GI tract melanoma is rare and almost always reported as a solitary lesion. We are reporting a case of metastatic malignant melanoma with various areas of metastasis of unknown source. Case: A 55-year-old healthy man presented to our service for upper endoscopy with complaints of abdominal pain and weight loss. Upper endoscopy showed a 1.5 cm ulcerated nodule in the fundus with extrinsic impression. Colonoscopy showed 3-4 cm smooth ulcerated mass in the ascending colon (Figure 1). The patient had screening colonoscopy 5 years ago, which was normal. Biopsies came back with diagnosis of malignant melanoma on both gastric fundus and colonic masses. Further imaging showed bone, liver and pleural metastasis. No primary source was found on skin or ocular origin.FigureDiscussion: Primary GI tract melanomas are rare as most of GI melanomas are metastatic in origin. Primary gastric and colonic melanomas are rarely reported in the literature and almost always reported as solitary lesions without metastasis at time of diagnosis. Our patient presented with metastatic disease with no clear primary cutaneous or ocular source. The primary source could be previously regressed cutaneous melanoma or a primary GI (gastric or colonic) melanoma with secondary metastasis. Except for primary esophageal melanoma, no clear criteria have been suggested to differentiate a primary GI tract melanoma from a metastatic GI lesion. Conclusion: Further clinical and pathological studies are needed to differentiate primary versus metastatic GI melanomas in the absence of primary source. The ability to distinguish the two entities may change our current management.