Colorectal cancer is a type of cancer that begins in the colon or rectum, which are parts of the large intestine. These cancers are often grouped together because they share many similarities in how they develop and are treated.
Most colorectal cancers begin as small growths on the inner lining of the colon or rectum called polyps. Polyps are common, especially as people get older, and most are not cancer. However, some types of polyps can change into cancer over time, often over many years.
Adenomatous polyps, also called adenomas, are considered precancerous because they can develop into cancer. These include tubular, villous, and tubulovillous adenomas. Tubular adenomas are the most common, while villous adenomas are less common but more likely to become cancerous.
Other types of polyps, such as hyperplastic and inflammatory polyps, are usually not precancerous. However, certain serrated polyps, including sessile serrated polyps and traditional serrated adenomas, have a higher risk of turning into cancer and are often treated more carefully.
If a polyp was found to be cancerous, or if you had colorectal cancer symptoms that resulted in a diagnosis, biomarker tests will be run along with other tests to determine the extent of cancer.
Learn more about colorectal cancer staging.
