What Is Colorectal Cancer?

Colorectal cancer is indicated by malignant cells in the colon or rectum. The colon and the rectum are parts of the large intestine, which is part of the digestive system. Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer. Because colon cancer and rectal cancers have many features in common, they are often referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum also may spread to other parts of the body.

A type of cancer called adenocarcinoma accounts for more than 95% of cancers in the colon and rectum and is usually what is meant by the term "colorectal cancer." There are other types of cancer that can be found in the colon and rectum, but they are rare. Learn more about the types of colorectal cancer.

What is the difference between colon cancer and colorectal cancer?

Although cancer can develop in either the colon or the rectum or both, cancers in the large intestine are very similar in biology. Appearance and treatments are largely the same. Cancer in the colon is more common than cancer in the rectum. Learn more about diagnosing colorectal cancer.

Where is the colon and what does it do?

The large intestine is another name for the colon and the rectum—the two portions of your gastrointestinal tract responsible for the final stages of the body’s processing of food. The food you eat travels through the esophagus to the stomach to the small bowel. It moves on into the large intestine, traveling through the colon and then, finally, the rectum.

By the time your food reaches the large intestine, all vitamins and most nutrients have been removed to support your body’s activity. What remains is mostly liquid which the colon absorbs. The colon passes on the material that is still left after all the processing as waste that remains in the rectum for storage and eventual evacuation.