Metastatic Gastric Melanoma: A Challenging Diagnosis

Background The stomach is regarded as a rare site for metastasis. When a gastric mass is observed macroscopically, the presumed diagnosis is usually a primary gastric carcinoma. However, the stomach may be involved in metastatic malignant melanoma. Besides a possible macroscopical misdiagnosis, metastatic gastric melanoma may also be misdiagnosed microscopically as adenocarcinoma due to its protean histological characteristics. These features make metastatic gastric melanoma a challenging diagnosis in some cases. Case report We report a patient with metastatic gastric melanoma referred to us with an initial macroscopic and histopathological diagnosis of primary gastric adenocarcinoma. He was diagnosed as having metastatic gastric melanoma by further examination because of the peculiar metastatic involvement and normal gastrointestinal tumor marker levels. Conclusions The stomach may be involved in melanoma and melanoma metastasis to the stomach is a diagnosis that should be taken into account while evaluating any gastric mass lesion. It is likely to be encountered more commonly nowadays due to the significant increase in the melanoma incidence. A history of melanoma, an atypical metastatic pattern, and normal gastrointestinal tumor marker levels may contribute to its diagnosis.