Most polyps are small in size and usually do not cause any problems. They are benign and do not become cancerous. Larger benign polyps can interfere with health by making it more difficult to pass a bowel movement. Another type of colon polyp, called an adenoma, is potentially cancerous. Thirty percent of people over age 50 have at least one adenoma.
Some adenomas stay harmless.
However, others may turn into cancer. The larger the adenoma, the more likely that it will become cancerous. It takes about five years for a medium-size adenoma to develop and about ten years for a cancer to develop. This allows plenty of time to be tested. Polyps of any size can bleed, causing black tarry stools, red blood in the stool, and anemia.