Colon Cancer also known Colorectal cancer. Colon cancer 2nd most deaths for cancers in the US. Colon cancer is cancer that starts in the large intestine (colon) or the rectum (end of the colon). The colon is the part of the digestive system where the waste material is stored. The rectum is the end of the colon adjacent to the anus. Together, they form a long, muscular tube called the large intestine (also known as the large bowel). 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. Cancer of the colon or rectum is also called colorectal cancer. In the United States, it is the fourth most common cancer in men and women. It is the third most common form of cancer and the second leading cause of cancer-related death in the Western world. Colorectal cancer causes 655,000 deaths worldwide per year.Many colorectal cancers are thought to arise from adenomatous polyps in the colon. These mushroom-like growths are usually benign, but some may develop into cancer over time.
Colon cancer often causes no symptoms until it has reached a relatively advanced stage. Thus, many organizations recommend periodic screening for the disease with fecal occult blood testing and colonoscopy. 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. Most cases of colon cancer begin as small, noncancerous (benign) clumps of cells called adenomatous polyps. Polyps of the colon and rectum are almost always benign and usually produce no symptoms. They may, however, cause painless rectal bleeding or bleeding not apparent to the naked eye. There may be single or multiple polyps. Polyps greater than 1 centimeter have a greater cancer risk associated with them than polyps under 1 centimeter. Polyps with atypia or dysplasia are also more likely to progress on to colon cancer. The risk of cancer is much higher in sessile villous adenomas than in pedunculated tubular adenomas. Cancer is found in 40% of villous adenomas, as compared to 15% in tubular adenomas.
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