Introduction
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.
This National Cancer Institute (NCI) booklet (NIH Publication No. 03-1552) has important information about the possible causes, symptoms, diagnosis, and treatment of colorectal cancer. It also has information to help patients cope with the disease.
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:
- Telephone (1-800-4-CANCER): Information Specialists at NCI's Cancer Information Service can answer questions about cancer and can send materials published by NCI.
- Internet (): Cancer.gov is NCI's Web site. It has a wide range of information that is updated regularly. People can ask questions online and get immediate help through LiveHelp. Many NCI booklets and fact sheets can be viewed at http://cancer.gov/publications. People in the United States and its territories may use this Web site to order publications. This Web site also explains how people outside the United States can mail or fax their requests for NCI publications.
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.
Understanding Cancer
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.
Tumors can be benign or malignant:
- Benign tumors are not cancer:
- Benign tumors are rarely life-threatening.
- Generally, benign tumors can be removed, and they usually do not grow back.
- Cells from benign tumors do not invade the tissues around them.
- Cells from benign tumors do not spread to other parts of the body.
- Malignant tumors are cancer:
- Malignant tumors are generally more serious than benign tumors. They may be life-threatening.
- Malignant tumors usually can be removed, but sometimes they grow back.
- Cells from malignant tumors can invade and damage nearby tissues and organs.
- Cells from malignant tumors can spread to other parts of the body. The cells spread by breaking away from the original cancer (primary tumor) and entering the bloodstream or lymphatic system. They invade other organs, forming new tumors and damaging these organs. The spread of cancer is called metastasis.
Colorectal Cancer
Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer. Cancers affecting either of these organs may also be called colorectal cancer.
When colorectal cancer spreads outside the colon or rectum, cancer cells are often found in nearby lymph nodes. If cancer cells have reached these nodes, they may also have spread to other lymph nodes, the liver, or other organs.
When cancer spreads (metastasizes) from its original place to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if colorectal cancer spreads to the liver, the cancer cells in the liver are actually colorectal cancer cells. The disease is metastatic colorectal cancer, not liver cancer. It is treated as colorectal cancer, not liver cancer. Doctors sometimes call the new tumor "distant" or metastatic disease.
