What is colon cancer?The colon and rectum are organs of the digestive system. They are located in the abdomen between the small intestine and the anus. Together, the colon and rectum make up the large intestine or large bowel. Because of their close relationship, cancers of the two organs are often discussed together under the name colorectal cancer. Tumors of the colon and rectum are growths arising from the inner wall of the large intestine. Benign tumors of the large intestine are called polyps.
Malignant tumors of the large intestine are called cancers. Benign polyps do not invade nearby tissue or spread to other parts of the body. Benign polyps can be easily removed during colonoscopy, and are not life threatening. If benign polyps are not removed from the large intestine, they can become malignant (cancerous) over time. Most of the cancers of the large intestine are believed to have developed from polyps.
Colon cancer is the second most common cancer diagnosed in the United States. Epidemiological evidence has shown that a diet high in fat and low in fruits, vegetables, and fiber contributes to the development of the disease. Smoking is also a factor in some types of colon cancer. Statistically, a family history of colon cancer or cancer of the female reproductive organs, a history of colon polyps, or a history of ulcerative colitis puts one at a greater risk of developing colon cancer. Colon cancer is most common in people over age 50. Globally, cancer of the colon and rectum is the third leading cause of cancer in males and the fourth leading cause of cancer in females. The frequency of colorectal cancer varies around the world. It is common in the Western world, and is rare in Asia and Africa. In countries where the people have adopted western diets, the incidence of colorectal cancer is increasing.
Several genes that signal a hereditary predisposition to colon cancer have been identified. For example, mutations in either of two genes, MSH2 and MLH1, can predispose a person to hereditary nonpolyposis colorectal cancer (HNPCC). People in HNPCC families can undergo blood tests that can tell them whether they have an affected gene. With the information obtained from such screening, an appropriate course of preventive measures and follow-up tests can be initiated. Cancer of the colon and rectum (also referred to as colorectal cancer) can invade and damage adjacent tissues and organs. Cancer cells can also break away and spread to other parts of the body (such as liver and lung) where new tumors form. The spread of colon cancer to distant organs is called metastasis of the colon cancer. Once metastasis has occurred in colorectal cancer, a complete cure of the cancer is unlikely.