What is Colorectal Cancer?
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Colorectal cancer is cancer of the colon or the rectum. Colorectal cancer develops from polyps – small benign mounds of tissue that develop in the lining of the colon or rectum. Not all polyps become cancer, but those that have the potential to turn into cancer are called adenomas. An adenoma that has become cancer is a tumor. A tumor that is located in the cecum or ascending colon is a right sided colon lesion. A tumor located in the descending or sigmoid colon is a left-sided colon lesion. It may take ten years or more for the normal lining of the colon to develop an adenoma and for the adenoma to turn into a cancer. Gastroenterologists and surgeons can remove these precancerous polyps during a colonoscopy, and significantly reduce the risk of colon cancer. Most colorectal cancers (over 95 percent) are called adenocarcinomas.
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 A close-up view of how a polyp may form in the colon.
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