Blog Archive ? Hereditary nonpolyposis colorectal cancer

21
Feb

Colorectal cancer, also called colon cancer or rectal cancer, is cancer of the large intestine or bowel. Most cases start from polyps on the lining of the intestine. Polyps are small, mushroom-shaped growths, which most of the time are harmless. However, certain kinds, called adenomatous polyps, have the potential to become cancerous.

Colon cancer is among the most common types of cancer, with more than 104,000 new diagnoses each year. An additional 40,000 people are diagnosed annually with cancer of the rectum. Genetics plays a role: Up to 1 in 4 people with colon cancer have family members who have had the disease. Lifestyle is also a factor: People who aren?t physically active and who eat a high-fat or low-fiber diet are at increased risk.

The good news is that there are reliable tests to screen for precancerous polyps, and when detected early, both colon cancer and rectal cancer have high cure rates. Compliance with these screening guidelines may prevent cancer from occurring in the first place.

Need-to-know anatomy

The colon and rectum are part of the digestive system, which takes the food you eat, removes the nutrients?including proteins, fats, carbohydrates, and vitamins?and eliminates the wastes. The key component of this system is the digestive tract, a 28-foot-long hollow tube that includes the mouth, esophagus, stomach, small intestine, large intestine, and anus.

The last 5 to 6 feet of the intestine form the colon or large intestine. This structure has six major divisions: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The last 5 or 6 inches of the large intestine make up the rectum.

Familial adenomatous polyposis

FAP is an inherited condition caused by a mutation on chromosome 5. It is characterized by the growth of hundreds or thousands of polyps?abnormal, mushroom-like growths?inside the colon and rectum (and occasionally the stomach and small intestine, too). Other names for this condition include familial polyposis and Gardner?s syndrome. People with a mutation in the gene associated with FAP, known as APC, have a nearly 100 percent lifetime risk of developing colon cancer.

The polyps begin to appear during teen years and often become cancerous by age 40. They vary in size from less than one tenth of an inch to 1 to 2 inches. Indeed, some may be large enough to block part of the intestine. FAP may also be associated with benign tumors of the skin, soft connective tissue, and bones.

People with FAP have a 50 percent chance of passing the condition on to each of their children. The condition can be passed on even if the patient has had his or her own colon removed. Children of FAP sufferers who are lucky enough not to inherit the condition cannot pass it on to their own children. About one third of people with FAP do not have an affected parent but have a new or spontaneous mutation and can pass FAP on to their children. Genetic counseling is available and recommended for individuals with FAP and for their family members.

Some families are affected with attenuated FAP (AFAP). This is a mild form of FAP in which individuals develop fewer polyps at a later age than those with typical FAP. Although people with AFAP tend to develop colon cancer at a later age than individuals with typical FAP, they still have a near 100 percent lifetime risk of colon cancer. If AFAP is suspected within a family, it is important that family members be screened with colonoscopy rather than flexible sigmoidoscopy because polyps are not evenly distributed throughout the colon. The number of polyps and age of onset can vary greatly from one family member to another in a family with AFAP.

Regular screening is important because the symptoms of colon cancer may not occur until the disease is advanced. Examinations should begin by age 11 even in children who do not have symptoms. With FAP, abnormalities in other areas of the body may give early clues to its presence: bumps or lumps on the bones of the legs, arms, skull, and jaw; cysts of the skin; teeth that do not erupt when they should; and freckle-like spots on the inside lining of the eyes.

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Source: http://www.pursonalityplus.com/2012/02/21/hereditary-nonpolyposis-colorectal-cancer/

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