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Increasingly, direct genetic
testing for germline mutations in MLH1, MSH2, and MSH6
is used to diagnose hereditary
nonpolyposis colorectal cancer (HNPCC) in patients with
a suggestive personal or family history. In general, the following "red flags" in a patient 's personal or family history should raise suspicion for HNPCC:
Colorectal or endometrial cancer diagnosed prior to age 50
Two or more HNPCC-related cancers in an individual or a family51
According to recent American Gastroenterological Association (AGA) guidelines,32 genetic testing for germline mutations in HNPCC-related genes is indicated for:
Individuals with two HNPCC-related cancers (including synchronous/metachronous colorectal cancers)
Individuals with colorectal cancer who have a first-degree relative with an HNPCC-related cancer (or colorectal adenoma) with at least one of the cancers diagnosed before age 50 (adenoma diagnosed before age 40)
First-degree adult relatives of those with a known HNPCC mutation
Colorectal cancer patients whose tumor specimens are microsatellite instability high (MSI-H).
Genetic testing will allow
you to accurately identify patients with HNPCC and then adjust their medical management
accordingly.