An aggressive malignant melanocytic neoplasm that arises from the rectum. The disease is MONDO_0002167 (rectum malignant melanoma). Also known as: malignant melanoma of rectum, malignant melanoma of the rectum, melanoma (disease) of rectum, melanoma of rectum, melanoma of the rectum, rectal malignant melanoma, rectal melanoma, rectum melanoma.