A malignant epithelial neoplasm that arises from the rectosigmoid area and invades through the muscularis mucosa into the submucosa. The vast majority are adenocarcinomas. About 50% of colorectal carcinomas occur in the rectosigmoid area. The disease is Monarch Disease Ontology id MONDO_0002424 (rectosigmoid carcinoma). Also known as: carcinoma of rectosigmoid junction, rectosigmoid cancer, rectosigmoid junction carcinoma.