Colorectal cancer is a disease in which cancerous cells form in the tissues along the inner walls of the colon or rectum. The disease typically begins as benign tumors called polyps, which may remain in the colon for several years before becoming cancerous. While not all polyps become cancerous, a small percentage of them eventually do. Preventive colon cancer screening is available to identify and remove these polyps before they become cancerous. Unfortunately, many polyps are not identified and are allowed to progress into malignancy, resulting in a diagnosis of cancer.