S2225 A Rare Finding of Primary Cecal Melanoma as a Cause of Lower GI Bleed

Abstract

Introduction: Primary melanomas of the GI tract are relatively uncommon. Cases in the Gi tract have been confirmed in the esophagus, small bowel and anorectum from prior published reports. The occurrence of primary malignant melanoma or secondary primary melanoma in the colon is very rare. In this case, we report secondary primary melanoma presenting as lower GI bleed. Case Description/Methods: A 78-year-old male with history of melanoma of the scalp removed 10 years ago presented for anemia. GI was consulted for lower GI bleed. He underwent endoscopy and colonoscopy for evaluation of lower gastrointestinal bleed. Colonoscopy revealed a large circumferential ulcerative mass occupying the entirety of the cecum past the ileocecal valve. The biopsy showed sheets of malignant cells with prominent nuclear pleomorphism on a background of abundant necrosis. The pathology report was consistent with metastatic malignant melanoma based on morphology and immunophenotype. He underwent extensive workup to identify the primary lesion. PET-CT showed abnormal focal uptake only within the right colon and no other primary lesion identified. MRI brain with contrast did not show any abnormal enhancing lesions. The patient further underwent complete dermatological evaluation along with examining the previous melanoma area of the scalp. The conclusion was that the colonic mass is likely secondary primary melanoma (Figure). Discussion: Presentation of melanomas within the alimentary tract are usually metastatic in origin. The occurrence of melanoma in the colon is atypical, because melanocytes are embryologically absent in the large colon. In a 2018 report there were less than 35 cases of right colon melanoma reported up to that date. Primary melanoma survivors have an increased risk of second primary melanoma. A population-based study conducted from 1973-2006 that included 89,515 patients showed overall subsequent primary cancer increased to 28%. One quarter of these were subsequent melanoma. They also had an elevated risk of breast, prostate and Non-Hodgkins lymphoma. There were no reports of second primary colonic melanoma. Currently, there is no current guideline for screening for second primary colonic neoplasm. Treatment and diagnosis require a multidisciplinary treatment approach including chemotherapy, radiation, surgery and immunotherapy. This case demonstrates that even though it is rare, health care providers have to be cognizant about a possible second primary colonic melanoma in the setting of prior history of melanoma.Figure 1.: A: Colonoscopy image showing large circumferential ulcerative mass occupying the entirety of the cecum B: Colonoscopy imaging showing circumferential mass with blood clots identified at the cecum C: Abnormal Uptake in the right colon.