A colorectal polyp is a polyp (fleshy growth) occurring on the lining of the colon or rectum.Untreated colorectal polyps can develop into colorectal cancer. Colorectal polyps are often classified by their behaviour (i.e. benign vs. malignant) and/or etiology (e.g. as a consequence of inflammatory bowel disease). colorectal polyp is a polyp (fleshy growth) occurring on the lining of the colon or rectum.