Lynch Syndrome
Overview
Lynch syndrome is an inherited disorder that increases the risk of developing a range of different cancers including colorectal cancer, endometrial cancer, and ovarian cancer, often before the age of 50. It is also referred to as hereditary nonpolyposis colorectal cancer (HNPCC).
Lynch syndrome is caused by mutations (changes) in genes that are involved in DNA mismatch repair, a process that fixes mistakes that happen when DNA is copied. The genes involved in Lynch syndrome are MLH1, MSH2, MSH6, PMS2, and EPCAM.
People with Lynch syndrome may have benign (noncancerous) growths in the colon, or colon polyps, at a younger age than they would occur in the general population. High microsatellite instability (MSI-H), an important biomarker in colorectal cancer, is a hallmark of Lynch syndrome. MSI-H is an indication that sections of DNA (microsatellites) have become unstable because the DNA mismatch repair process is not functioning properly.
What are the signs of Lynch syndrome?
The Bethesda guidelines are a set of criteria that is used to help determine who should be tested for Lynch syndrome. The criteria are:
What are the signs of Lynch syndrome?
The Bethesda guidelines are a set of criteria that is used to help determine who should be tested for Lynch syndrome. The criteria are:
How is Lynch syndrome diagnosed?
Genetic testing can be performed on cancerous tissue to determine if Lynch syndrome is likely. The tests include microsatellite instability testing (MSI) and immunohistochemistry testing (IHC). A blood or saliva test can be done to confirm Lynch syndrome.
How does colorectal cancer screening change for Lynch syndrome?
Since individuals with Lynch syndrome have a higher risk of developing colorectal cancer, they will follow different screening guidelines compared to the general population. If an individual is diagnosed with Lynch syndrome, a genetic counsellor will develop a personalized screening program based on family history of cancer and any genetic testing done in the family.
Guidelines for men and women who have Lynch syndrome indicate that colorectal cancer screening should usually begin at age 25, OR 5-10 years before the earliest age of colorectal cancer diagnosis in the family, whichever comes first. For example, if a mother is diagnosed with colorectal cancer at 28, her children should begin screening at 18-23 years of age. Colonoscopy should take place every 1-2 years until age 40. A genetic counsellor will determine the optimal approach to screening for cancer risk reduction.
It is also important to be aware of common signs of colorectal cancer and bring any new concerns to a doctor’s attention. Symptoms of colorectal cancer include:
