Colon or rectal cancer is an abnormal growth of cells in the colon or rectum. The growth of cells is called a malignant tumor. The colon and rectum are sections of the large intestine, also called the large bowel. The colon is the first part of the large bowel. It is nearly 5 feet long. The rectum is the last few inches of the large bowel. The rectum is at the end of the colon and just above the anus.

It is important to diagnose and treat colon or rectal cancer as soon as possible. If not treated, the cancer can spread through the bowel wall to lymph nodes and the bloodstream and to other parts of the body.

The large intestine is one of the 4 most common sites for cancer to occur. (The other 3 most common sites are the lungs, the breasts, and the prostate.)

Another name for this type of cancer is colorectal cancer.
 

Cancer cells are abnormal cells that grow in an uncontrolled way. They can spread (metastasize) beyond where they start. Most colorectal cancers start from a type of polyp called an adenomatous poly. Polyps are extra tissue that grow on the inside wall of the bowel.

Colorectal cancer is more common in countries where obesity is common, where the diet is high in fat and low in fiber, and where daily exercise is less common. It is not known how this combination of obesity, diet, and lack of exercise combine to increase the risk for colorectal cancer. Colon or rectal cancer usually occurs after age 50, but it can happen at any age.

You have a greater risk of developing colon cancer if you:

• have a personal or family history of colon cancer, polyps, or inflammatory bowel disease
• have had uterine, ovarian, or breast cancer
• eat a high-fat and low-fiber diet.
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