Overview

Sporadic colorectal cancer accounts for 75% of all cases and mostly occurs in persons over 50 years of age. Inherited genetic mutations account for 5% of cases, whereas familial colorectal cancer occurs in 20% of cases where there is no identifiable hereditary syndrome, suggesting genetic contribution and/or common exposures in these families. Hereditary nonpolyposis colorectal cancer accounts for 2-5% of all colon cancers. It has autosomal dominant inheritance pattern with gene penetrance for colon cancer of approximately 70-85%. Hereditary nonpolyposis colorectal cancer gene carriers also have increased risk for malignancy at several extracolonic sites (Lynch II or cancer family syndrome), primarily endometrial (5-10% of all endometrial cancer cases), gastric, hepatobiliary, pancreatic, renal pelvis, ovarian, brain, and small bowel carcinoma.[1] The risk of endometrial cancer is 40-60%, and the risk of all other extracolonic cancers is less than 10-15%. Furthermore, two other named familial syndromes are associated with HNPCC. The combination of HNPCC and cutaneous lesions such as adenomas, eptheliomas, carcinoma, keratoacanthomas, and epidermal cysts is known as Muir-Torre syndrome. The combination of HNPCC and CNS lesions, specifically glioblastoma multiforme, is known as Turcot's syndrome.

Hereditary nonpolyposis colorectal cancer results in accelerated tumorigenesis from polyp to cancer in 1-2 years. Males have overall increased risk, with early age of onset about 45 years. HNPCC-related colorectal cancer accounts for 15-20% of all colorectal cancers diagnosed before the age of 45. Clinicopathological features of colorectal cancers in HNPCC are summarized in Table 1. Multiple colon cancer develops both synchronously and metachronously in patients with less than total abdominal colectomy[2] (about 40% within 10 years). In patients treated with total colectomy and ileorectal anastomosis, the risk of rectal cancer is 1% per year for the first 12 years making annual endoscopic examination of the rectal stump mandatory.[3] In HNPCC syndrome, endometrial and ovarian cancers have a similar mean age at onset (during the fourth decade) to colorectal cancer and usually precede that of sporadic gynecologic malignancy by 15 years. The risk of endometrial cancer (60%) in mutationpositive women exceeds that of colorectal cancer (54%).[4] Ovarian cancer occurs 3.6-13 times more frequently than expected in the general population.1-4-1

10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

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