2610 Metastatic Melanoma Mimicking Enteritis

Abstract

INTRODUCTION: Metastasis of melanoma to the gastrointestinal tract is rarely identified in clinical practice. We relay the case of a patient presenting with abdominal pain and leukocytosis with CT imaging initially suspicious for infectious or inflammatory bowel disease, but later confirmed to be small bowel melanoma. This report highlights the unpredictable nature of melanoma and underscores the need to be cognizant of imaging and endoscopy limitations in identifying disseminated disease. CASE DESCRIPTION/METHODS: A 59-year-old man with no past medical history presented to the ED with a one-day history of nausea associated with severe right lower quadrant abdominal pain. Labs showed leukocytosis to 20 K/uL. CT of the abdomen and pelvis showed significant wall thickening of a long segment of distal small bowel loop with adjacent fat stranding. He was discharged with antibiotics for presumed infectious enteritis and with gastroenterology follow up. Patient underwent ileocolonoscopy one month later that was significant for multiple polyps but otherwise normal appearing ileum and biopsies were negative for colitis or ileitis. Two months later, during follow up, patient underwent MR enterography which showed large mass measuring 9.0 × 7.1 × 7.4 cm in size in the small bowel, correlating with area of thickened bowel noted on CT previously (Figure 1). Patient underwent exploratory laparotomy with resection of small bowel mass with pathology positive for melanoma (Figure 2). Primary site was identified shortly thereafter as a cutaneous lesion in area of right upper back. DISCUSSION: Delayed diagnosis in this case hinged on unrevealing colonoscopy and CT findings describing only distal small bowel wall thickening concerning for enteritis due to infection or inflammatory bowel disease. Bender et al reported a sensitivity of 66% for contrast-enhanced CT in demonstrating intestinal metastatic deposits. A less common radiographic manifestation of metastatic melanoma infiltrating the serosa described in the literature includes segmental circumferential bowel thickening that can mimic the appearance of Crohn’s disease or intestinal enteritis, a characteristic that might explain the CT findings described in our patient. Also of note is the inability of endoscopy to uncover serosal metastases which is especially concerning as it is common for intestinal melanoma metastases to grow extraluminally.