Primary colonic malignant melanoma

Primary malignant melanoma originating in the digestive tract is extremely rare. A case of primary malignant melanoma in the descending colon is described. The tumor was an elevated mass with surface necrosis. Histologically, tumor cells were arranged with compact nests surrounded by fibrous stroma. The tumor cells had pleomorphic nuclei and rich cytoplasm. In some areas, cells of signet ring‐like appearance were found. An immunohistochemical...