Virginia Commonwealth University

VCU Massey Cancer Center

What is colorectal cancer?

The colon and the rectum are part of the large intestine, which is part of the digestive system. Malignant tumors can be found in either the colon or rectum. The colon or large bowel, includes the first 6 feet of the large intestine, and the rectum and the anal canal includes the last 6 inches. Because colon cancer and rectal cancers have many features in common, they are sometimes referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum also may spread to other parts of the body.

Colorectal cancer is the third most common cancer in both men and women. However, the number of new cases of colorectal cancer and the number of deaths due to colorectal cancer have decreased, which is attributed to increased screening and polyp removal.

Anatomy of the colon

The colon is the large intestine. It has four sections:

  • The first section is called the ascending colon. It extends upward on the right side of the abdomen.
  • The second section is called the transverse colon since it goes across the body to the left side. 
  • There it joins the third section, the descending colon, which continues downward on the left side. 
  • The fourth section is known as the sigmoid colon because of its “S” shape.

The sigmoid colon joins the rectum, which, in turn, joins the anus, or the opening where waste matter passes out of the body.