The exact causes of colorectal cancer are unknown, but half of all people develop colorectal polyps. Polyps are small growths that can become cancerous over time. Finding pre-cancerous polyps decreases the risk of colorectal cancer.
Most adults cannot get colorectal cancer if they do not have polyps. Less than 5 out of 100 colorectal cancers occur without any polyps (growths). Colorectal cancer without polyps usually occurs in people who are at increased risk for colorectal cancer because of either a hereditary syndrome called hereditary non-polyposis colon cancer or long-term inflammatory bowel disease.