S2223 Dead End in the Small Bowel: Rare Case of Small Bowel Melanoma Presenting as Melena

Abstract

INTRODUCTION: Malignant melanoma accounts for only 1% of all malignant tumors of the small bowel. The majority are usually metastatic from the skin eye or anorectum. Less than 50 cases of truly primary small bowel melanomas have been described in literature with overt bleeding as a presenting complaint even rarer. We present such a case of an elderly man with middle gastrointestinal bleeding who was found to have unresectable small bowel melanoma on device assisted enteroscopy. CASE DESCRIPTION/METHODS: An 80-year-old man with stage IV Chronic kidney disease presented to the hospital with a few months of dark tarry stools and symptomatic iron deficiency anemia refractory to iron supplementation needing up to 7 transfusions. He did not endorse Non-steroidal anti-inflammatory drug use. An esophagoduodenoscopy and colonoscopy at an outside facility was unremarkable. Video capsule endoscopy showed hematin in the the proximal jejunum with a possible ulcer more distally. A single balloon enteroscopy revealed a 10 mm cratered jejunal ulcer with slight pigmentation in the base (Figure 1). This was biopsied. Pathology revealed malignant melanoma with BRAF V600E mutation. Subsequent positron emission tomography (PET) showed a 6 cm small bowel mass compatible with primary site and metastatic lesions in the mesentery, perihepatic and subdiaphragmatic region (Figure 2). Following tumor board discussion, he was referred for palliative radiotherapy. DISCUSSION: Primary mucosal melanoma most commonly arises from the anal canal (31.4%), rectum (22.2%) and oropharynx (33%). Only 2.3% of cases have been reported from the small bowel. Presence of melanocytes has not yet been demonstrated in the small intestine, and the origin of primary melanoma of the small intestine remains unknown. Blecker et al. suggested a strict criteria for the diagnosis of primary intestinal melanoma: no evidence of concurrent cutaneous lesions, absence of extraintestinal metastatic spread of melanoma, and presence of intramucosal lesions in the overlying intestinal epithelium. This form of melanoma is more aggressive and associated with worse prognosis. Other factors of poor prognosis include lymph node involvement, advanced age and failure to undertake surgical resection (which remains the primary treatment option). Our case highlights the importance of keeping a broad differential in patients presenting with middle GI bleeding and aggressively pursuing tissue diagnosis in such cases.Figure 1.: Proximal Jejunum ulcer.Figure 2.: PET scan image with metastatic melanoma.