2755 Metastatic Melanoma of the Stomach

Abstract

INTRODUCTION: The GI tract is rarely affected by secondary tumors. One of the most common primary malignancies is melanoma, however, the stomach is a rare location for metastasis of malignant melanoma. We present a rare case of a patient who developed metastatic melanoma to the stomach. CASE DESCRIPTION/METHODS: An 82-year-old male with a prior history of melanoma presented with a chief complaint of hematemesis. Two weeks earlier, the patient had discovered an enlarged left axillary lymph node. His oncologist acquired a PET scan which demonstrated lower lobe pulmonary nodules and left axillary adenopathy. A biopsy of the axillary lymph node revealed metastatic melanoma. On the day of admission, he had several episodes of dark bloody emesis. Initial laboratory workup revealed a hemoglobin of 4.4. The patient was resuscitated and subsequently underwent an endoscopy. Innumerable black nodules were found scattered throughout the duodenum and stomach (Figure 1) along with a large ulcerating nodule with a depressed black center in the body of the stomach (Figure 2). Multiple cold biopsies revealed infiltration of the duodenal and gastric mucosa with discohesive malignant cells, abundant mitotic figures, and focal pigment formation. Immunohistochemical stains showed the cells to be positive for SOX10 and Melan-A (Figure 3). This confirmed metastatic melanoma within the upper GI tract and oncology was consulted for further management. DISCUSSION: The most common gastrointestinal metastatic sites from melanoma are the small bowel, followed by the colon, rectum and then stomach. The stomach is a rare location with a reported incidence of only 7%. Patients often present at an advanced stage of disease and prognosis is dismal. Median survival period from diagnosis is 4-6 months. Diagnosis is not commonly made before endoscopy as associated symptoms are non-specific and rarely present. Endoscopically, gastric melanomas are classified into 3 main morphological types: ulcerated melanotic nodules, submucosal masses with ulcerations, and mass lesions with necrosis and melanosis. The classic appearance is multiple, small nodules that can be pigmented or ulcerate to produce a bulls-eye appearance. The mechanisms underlying metastatic melanoma to the stomach are unclear. Four pathways may be involved in the metastatic spread of primary cancers to the stomach which includes peritoneal dissemination, hematogenous dissemination, lymphatic spread, and direct tumor invasion.