Colon polyps are protrusions that can arise from the surface of the colon (also known as the large intestine), according to the National Digestive Disease Information Clearinghouse. They are precursors to colon cancer, one of the most common cancers in the United States. Colon polyps can usually be removed during colonoscopy, a test in which a doctor examines the colon with a scope. There are three types of colon polyps.
Adenomatous Polyps
Adenomatous polyps (also known as adenomas) are polyps that can cause colon cancer. Adenomatous polyps are considered by pathologists to be benign tumors, which can grow larger and become cancerous if left alone. It is believed that 90 to 95 percent of all colon cancers arise from adenomas. This explanation of the origin of colon cancer is often referred to as the adenoma-carcinoma sequence.
Adenomatous polyps are equally distributed through out the colon, according to the book "Clinical Oncology" by Martin Abeloff. The risk of developing adenomatous polyps increases with age. In a 2007 study published in "Statistics in Medicine," researchers reported that 30 to 40 percent of adults have at least adenoma in their colon by the age of 60.
Adenomas are often classified as either tubular or villous adenomas, according to their histology (structure). Villous adenomas are the most dangerous. The incidence of cancer in villous adenomas ranges from 30 to 70 percent.
Inflammatory Polyps
Inflammatory polyps are the result of inflammation of the colon. These polyps often occur in association with inflammatory diseases of the gastrointestinal tract such as Crohn's disease, ischemic colitis and infectious colitis. The risk of developing cancer cells in inflammatory polyps is small.
Hyperplastic Polyps
Hyperplastic polyps are small growths in the colon that never become cancer. They account for 10 to 30 percent of all polyps in the colon. They typically do not exceed 10 mm in size.
