Colorectal Cancer Basics

Key Points

  • Colorectal cancer is a disease in which cells in the colon or rectum grow out of control.
  • If you are 45 years old or older, talk to your doctor about screening.
Photo of a doctor showing an model of the colon

What it is

Cancer is a disease in which cells in the body grow out of control. When cancer starts in the colon or rectum, it is called colorectal cancer. Sometimes it is called colon cancer, for short. The colon is the large intestine or large bowel. The rectum is the passageway that connects the colon to the anus.

Diagram of the stomach, small intestine, cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum
Location of the stomach, small intestine, cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.

Sometimes abnormal growths, called polyps, form in the colon or rectum. Over time, some polyps may turn into cancer. Screening tests can find polyps so they can be removed before turning into cancer. Screening also helps find colorectal cancer at an early stage, when treatment works best.

If you are 45 years old or older, talk to your doctor about screening. If you think you may be at increased risk for colorectal cancer, speak with your doctor about when to begin screening, which test is right for you, and how often to get tested.