Giant gastric metastasis of malignant melanoma.

Malignant melanoma is a highly aggressive skin cancer with high metastatic potential. While gastric metastases are generally asymptomatic, patients can present with nausea, vomiting, gastrointestinal bleeding, weight loss and perforation [1-3].

An 82-year-old woman presented with melena. She has been diagnosed with acral lentiginous melanoma of the fourth left toe with lymph node and bone metastases. The primary tumor was nodular with superficial ulceration and had been treated by surgical resection. The patient developed immune-related adverse events of arthritis and colitis due to nivolumab and was treated with prednisolone. Upon presentation, vital signs were stable and physical examination was unremarkable. Laboratory values were notable for moderate anemia and azotemia. Computed tomography with contrast revealed a large, enhancing space-occupying lesion in the body of the stomach (Fig. 1a). Esophagogastroduodenoscopy revealed a white semi-circumferential ulcerated mass measuring 10 cm in the gastric body (Fig. 1b). Hematin remaining in the stomach suggested recent bleeding, but no hemostatic measures were required. Biopsies of the lesion revealed histology which was strikingly similar to the resected skin lesion, staining positive for Melan A (Fig. 1c), HMB-45, SOX-10, S100. The patient was diagnosed with gastric metastasis of malignant melanoma. No recurrence of bleeding was observed after palliative radiotherapy, but the patient succumbed to metastatic disease 3 months later.

Figure 1

(a) Computed tomography with contrast revealed a large, enhancing space-occupying lesion in the body of the stomach. (b) Esophagogastroduodenoscopy revealed a white semi-circumferential ulcerated mass (arrows) measuring 10 cm in the lesser curvature of the gastric corpus. (c) Histology of the gastric biopsy (high-power magnification) with positive immunohistochemical staining for Melan A.

Gastric malignant melanoma may appear as single or multiple polypoid, sessile or ulcerated lesions on endoscopy [2]. A majority arise in the gastric corpus or fundus, occurring only rarely in the lesser curvature [4]. Hemostasis of gastric metastases with palliative radiation has been reported [2,5]. Metastatic malignant melanoma should be included in the differential diagnosis of gastrointestinal bleeding in patients with a history of malignant melanoma. The use of corticosteroids for immune-related adverse events may have played a role in exacerbating the ulceration of the giant metastatic lesion in this case.