Primary Gastric Melanoma With Pancreatic Metastasis: A Case Report

We report an extremely rare case of primary gastric melanoma with pancreatic metastasis. As far as we know, the concept of primary gastrointestinal melanoma is currently controversial, because there are very few reports of primary gastrointestinal melanoma. At the same time, isolated pancreatic metastases are also very rare. The patient was admitted to the hospital with a main complaint of decreased appetite, and then underwent gastroscopy and found a mass in the stomach. The mass was initially diagnosed as poorly differentiated adenocarcinoma following a gastroscopic biopsy. The patient underwent radical total gastrectomy, pancreatic body and tail resection, splenectomy, and Roux-en-Y esophagojejunostomy. After further immunohistochemical examination of the surgically removed tissue, malignant melanoma was diagnosed. The tumor cells were arranged in sheets or nests with infiltrating growth, the cell sizes were inconsistent, nucleoli were obvious, and melanin particles were seen in the cytoplasm of some cells. The tumor cells were positive for MITF and S-100. Detailed systemic and imaging examinations did not find any other primary lesions. The patient denied any melanoma and skin lesion history. We believe this is a manifestation of primary gastric melanoma. We report this rare case of gastric melanoma with the aim of increasing clinicians' awareness of non-cutaneous melanoma and its treatment methods.