ONCOLOGY Vol 19 No 4

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What the Physician Needs to Know About Lynch Syndrome: An Update

April 1st 2005

The Lynch syndrome (hereditary nonpolyposis colorectal cancer[HNPCC]), is the most common form of hereditary colorectal cancer(CRC), accounting for 2% to 7% of all CRC cases. The next most commonhereditary CRC syndrome is familial adenomatous polyposis (FAP),which accounts for less than 1% of all CRC. Lynch syndrome is ofcrucial clinical importance due to the fact that it predicts the lifetimerisk for CRC and a litany of extra-CRC cancers (of the endometrium,ovary, stomach, small bowel, hepatobiliary tract, upper uroepithelialtract, and brain) through assessment of a well-orchestrated family history.A Lynch syndrome diagnosis is almost certain when a mutation ina mismatch repair gene-most commonly MSH2, MLH1, or, to a lesserdegree, MSH6-is identified. Once diagnosed, the potential for significantreduction in cancer-related morbidity and mortality through highlytargeted surveillance may be profound. Particularly important iscolonoscopy initiated at an early age (ie, 25 years) and repeated annuallydue to accelerated carcinogenesis. In women, endometrial aspirationbiopsy and transvaginal ultrasound are important given the extraordinarilyhigh risk for endometrial and ovarian carcinoma. Thesecancer control strategies have a major impact on at-risk family membersonce they have been counseled and educated thoroughly aboutLynch syndrome’s natural history and their own hereditary cancer risk.