Current research shows that it takes about ten years for an adenoma polyp to turn into colon cancer. The majority of colon polyps are non-cancerous. The ones that have the
ability to become cancerous are called adenomas. Colonoscopies are usually performed every ten years on patients because that is the time frame for a polyp to become cancerous. All polyps found during a colonoscopy are usually removed and tested for cancer. Larger adenomas usually have more cancerous cells, or are already cancerous. The American College of Gastroenterology has excellent information on colon polyps at http://www.acg.gi.org/patients/gihealth/colonpolyps.asp. Not all colon cancers result from colon polyps, but the majority do, which is why it is important to get colonoscopies.