[The Diagnosis of Metastatic Malignant Melanoma Incidentally Found during a National Health Screening Endoscopy: A Case Report].

Malignant melanoma is one of the most common malignant diseases of the gastrointestinal tract. It has been reported that the malignant melanoma metastasizes not only to the small intestine due to the abundant blood supply, but also to the stomach, colon, and esophagus. Gastrointestinal metastasis is usually suspected depending on the clinical symptoms, as well as based on radiological or endoscopic findings. Imunohistochemical stains, such as Melan-A/Melanoma antigen recognized by T cell-1 or human melanoma black-45, are useful for confirming the diagnosis of malignant melanoma. A 44-year-old male received an operation due to a malignant melanoma at the left thumb two years ago. On the national health screening endoscopy, a submucosal tumor with hyperemic change on the top was found. The final diagnosis was a metastatic malignant melanoma in the stomach, pancreas, and pelvic bone. We recommend that endoscopists should consider the potential malignancy of subepithelial tumor with mucosa change, despite the tumor size being less than 1 cm.