Colon polyps are growths of tissue inside the large intestine, also called the colon. Some polyps are mushroom-shaped protrusions on the end of a stalk. Others appear as bumps that lie flat against the intestinal wall.
There are several types of polyps. Most are noncancerous (benign), but one type, the adenomatous polyp, is associated with changes (called mutations) in the DNA of the lining of the colon. These mutations can progress into colon cancer. The larger the polyp, the greater the chance that it contains cancerous cells.
Some people are born with a genetic tendency to develop multiple polyps. Inherited conditions such as familial adenomatous polyposis and Gardner's syndrome can cause hundreds of polyps to grow in the colon and rectum. Without surgery to remove the affected section of the intestine, it is almost certain that at least one of these polyps will turn into cancer by middle age. These two conditions are rare.