Cancer of the colon or rectum is also called colorectal cancer. In the United States, colorectal cancer is the fourth most common cancer in men, after skin, prostate, and lung cancer. It is also the fourth most common cancer in women, after skin, lung, and breast cancer.
Scientists are studying colorectal cancer to learn more about it. They are finding out more about its causes and are exploring new ways to prevent, detect, and treat it. This research is increasing our knowledge about colorectal cancer. The NCI provides the most up-to-date information by telephone and on the Internet:
The Colon and Rectum
The colon and rectum are parts of the digestive system. They form a long, muscular tube called the large intestine (also called the large bowel). The colon is the first 4 to 5 feet of the large intestine, and the rectum is the last 4 to 5 inches. The part of the colon that joins to the rectum is the sigmoid colon. The part that joins to the small intestine is the cecum.
Partly digested food enters the colon from the small intestine. The colon removes water and nutrients from the food and stores the rest as waste. The waste passes from the colon into the rectum and then out of the body through the anus.
Cancer begins in cells, the building blocks that make up tissues. Tissues make up the organs of the body.
Normally, cells grow and divide to form new cells as the body needs them. When cells grow old, they die, and new cells take their place.
Sometimes this orderly process goes wrong. New cells form when the body does not need them, and cells do not die when they should. These extra cells can form a mass of tissue called a growth or tumor.