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"Can genetic testing detect HNPCC?"


My family has a history of colon cancer. I am a 42 year old woman. Will genetic testing tell me about this?


Colon cancer is highly influenced by genetic factors. While the overwhelming majority of colon cancers that run in families are influenced by genetics but are not determined by any single gene, a certain subset of colon cancers fall into one of two cancer syndromes: FAP (familial adenomatous polyposis) and HNPCC (heriditary non-polyposis colon cancer). FAP is a disease caused by mutations in the APC gene, which predisposes patients to thousands of colonic polyps early in life and an extraordinarily high lifetime risk of colon cancer.

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HNPCC, known as Lynch Syndrome, is a genetic disease predisposing patients to colon cancer, but these patients have an average burden of colon polyps prior to developing colon cancer. Another hallmark of HNPCC is the presence of multiple cancers, with 7 to 10% of patients having had more than one type of primary cancer (such as ovarian, upper urologic tract, upper GI, skin, or brain cancers) at the time of diagnosis. There are actually multiple genes involved in DNA mismatch repair in which mutations have been demonstrated to produce the HNPCC syndrome and genetic tests are available for most of the common mutations causing the disease. The utility of genetic testing is another issue all together. As I said earlier, the vast majority of all colon cancers, even in people with a strong family history of colon cancer, are not due to either FAP or HNPCC. The most clearly defined role for genetic testing is in individuals who have a history of diagnosed FAP or HNPCC in their family. For other patients, the role is less clear, but genetic testing may still be indicated if though to be useful by your physician. I recommend you see either your primary care physician or a specialist such as a gastroenterologist to discuss the history of colon cancer in your family and what testing may be indicated, as well as the frequency of screening that would be most appropriate for you. Colon cancer is a serious disease and there is no substitute for consultation in person with a licensed physician familiar with the disease.

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