The colon and rectum are part of the digestive tract. They comprise the large intestine, or large bowel, which is located in the abdomen between the small intestine and the anus.
Colon cancer is cancer of the large intestine (colon), which is the lower part of the digestive system. Rectal cancer occurs on the last eight to ten inches of the colon. They are often referred to together as colorectal cancers, and are the second-leading cause of cancer-related deaths in the United States.
The incidence is slightly higher in men than women, and is highest in African American men. The incidence of colorectal cancer is highest in developed countries such as the United States and Japan, and lowest in developing countries such as Africa and Asia. Ashkenazi Jewish individuals have a higher incidence of a specific genetic mutation (called I1307K) that increases the risk for colorectal cancer.
Most colon cancers are adenocarcinomas (cancer in the glands or secretory cells) that develop when a change occurs in cells that line the wall of the colon or rectum. The disease often begins as an intestinal polyp, also called an adenoma, which is an abnormal growth of tissue. Polyps can gradually become precancerous and then cancerous.
The American Cancer Society's estimated number of new cases from colon and rectal cancer in the United States in 2012 are as follows: new cases: 103,170 (colon); 40,290 (rectal).
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