A Rare Case of Antemortem Metastatic Gastric and Small Intestine Melanoma

Abstract

Gastrointestinal (GI) metastatic melanoma most commonly involves the small bowel; however, it is often discovered posthumously. Here, we present a rare case of antemortem metastatic gastric and small intestine melanoma. A 70 year-old male with a history of right hallux acrolentiginous melanoma, previously in remission following adjuvant chemoradiotherapy, was referred to our gastroenterology clinic for evaluation of new gastric and duodenal lesions seen on routine surveillance PET scan. The patient had a several month history of early satiety with labs remarkable for a new, asymptomatic microcytic anemia. Small bowel enteroscopy was performed, notable for a 3 cm ulcerated mass in the gastric fundus with two 5 mm pigmented masses along the lesser curvature of the gastric body with superficial ulcerations. A 2 cm ulcerated mass was also visualized in the 3rd portion of the duodenum. Numerous biopsies were performed, all consistent with metastatic melanoma. The patient was initiated on pembrolizumab and ipilimumab but unfortunately developed progressive disease with increasing size of gastric and duodenal masses with new jejunal lesions on repeat push enteroscopy 9 months later. Melanoma is one of the most common malignancies associated with metastases to the GI tract with up to 60% of patients with evidence of metastatic disease at autopsy. However, less than 5% of these cases are diagnosed antemortem given the rather non-specific clinical manifestations. In particular, the diagnosis of gastric involvement prior to autopsy is rather rare with a limited body of existing case reports. Median survival for metastatic GI melanoma is less than one year. Primary systemic therapy for metastatic disease often involves use of checkpoint inhibitor immunotherapy. There are no standardized criteria for the operative management of metastatic gastrointestinal melanoma but surgery may be appropriate in patients presenting with acute abdominal emergencies or for palliation. Although our patient was referred for suspected metastatic disease, clinicians must always maintain a high index of suspicion for gastrointestinal involvement in any patients with a history of metastatic melanoma with vague abdominal complaints.2639_A Figure 1. 5 mm ulcerated lesion (metastatic melanoma) along lesser curvature of stomach2639_B Figure 2. 3 cm ulcerated mass (metastatic melanoma) in gastric fundus2639_C Figure 3. Large ulcerated mass in the gastric fundus on repeat enteroscopy demonstrating significant progression from prior endoscopy