Lynch syndrome is the cause of 2 percent to 7 percent of new colorectal cancers diagnosed each year.
Lynch syndrome is caused by a mutation in DNA repair genes. The four genes, MLH1, MSH2, MSH6, and PMS2, are responsible for 32 percent, 38 percent, 14 percent and 15 percent of cases, respectively.
Lifetime cancer risk for those with Lynch syndrome depends on several factors, including which gene is present and prevention behaviors. The following table summarizes overall lifetime cancer risks.
|Lynch Syndrom||Mean Age
|Hepatobillary tract||<1%||2-18%||Not reported|
|Upper urinary tract||<1%||Overall: 8.4%;
up to 27% in men
|Small bowel||<1%||3-6%||49 years|
|Brain/central nervous system||<1%||4%||~55 years|
|Sebaceous neoplasms||<1%||1-9%||Not reported|
You should suspect Lynch syndrome if a patient has a family history of cancer, especially if there are:
Taking a family health history is the first step, but the fact that it may be caused by different mutations in one of several genes complicates diagnosis and testing. Genetic testing can be done to confirm if a person has a mutation, but it is not always useful to test everyone in the family for Lynch syndrome. It is best to test the person who has the cancer for Lynch syndrome before testing others in their family. Identifying Lynch syndrome also involves a combination of various genetic and immunohistochemical tests to first establish the probability of Lynch syndrome and then identify which gene is most likely causing the cancer.
The only proven ways to reduce cancer risk is frequent cancer screenings and preventative prophylactic surgery when appropriate. Some resources on cancer screening guidelines are below.
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