Most cases of colon cancer begin with the development of benign intestinal polyps. Benign polyps are relatively common in people over the age of 50, and while most do not cause health problems, some can become cancerous and potentially spread to other parts of the body (metastasize). These finger-like growths protrude into the intestinal cavity (lumen) or the rectum. They can be fragile and bleed intermittently, such as when food waste brushes against them.