About Colorectal Cancer

Colorectal cancer occurs in one of two parts of your large intestine:

  • the colon, a muscular five- to six-foot-long tube that absorbs water and nutrients from food
  • the rectum, the bottom six inches of the large intestine, where stool collects and then passes out of the body through the anus during a bowel movement

Lower GI TractLower GI Tract
Most colorectal cancers begin in the innermost layer of your sigmoid colon, which is just above your rectum. How far it spreads through the sigmoid layers determines the cancer’s stage, or how advanced it is.

Colorectal cancer grows slowly over several years. It starts as small, abnormal growths projecting from the surface of the colon called polyps. Some of these polyps can eventually turn into cancer. A small percentage of colorectal cancers — usually hereditary forms of the disease — can cause large numbers of polyps to appear, but these types are rare.

Colorectal cancer is usually contained within the colon, but when it becomes advanced, the cancer can metastasize (spread) to other organs. When colorectal cancer spreads, it most often moves to the liver and lungs.

The colorectal cancer experts at Memorial Sloan Kettering use physical examinations and diagnostic and imaging tests to confirm a diagnosis or determine the stage of the disease.