Lynch syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC), is the most common cause of hereditary colorectal (colon) cancer.
People with Lynch syndrome are more likely to get colorectal cancer and other cancers, and at a younger age (before 50), including
- Uterine (endometrial),
- Brain, and
- Certain types of skin cancers.
Lynch syndrome causes about 4,200 colorectal cancers and 1,800 uterine (endometrial) cancers per year.
Genetics and Lynch syndrome
Lynch syndrome is due to inherited changes (mutations) in genes that affect DNA mismatch repair, a process that fixes mistakes made when DNA is copied. These genes (MLH1, MSH2, MSH6, PMS2, and EPCAM) normally protect you from getting certain cancers, but some mutations in these genes prevent them from working properly.
Everyone has two copies of each of the genes involved in Lynch Syndrome, one from their mother and one from their father. Even if a person inherits a mutation in a Lynch syndrome gene, they still have the normal copy of the gene from the other parent. Cancer occurs when a second mutation affects the normal working copy of the gene, so that the person no longer has a copy of the gene that works properly. Unlike the inherited Lynch syndrome mutation, the second mutation would not be present throughout the person’s body, but would only be present in the cancer tissue. However, not everyone with Lynch syndrome will get cancer.
Colorectal cancer also can be caused by mutations in genes other than those related to Lynch syndrome. This means that some families with a history of colorectal cancer will not have mutations in a Lynch syndrome gene. These mutations might be picked up through genetic testing using multigene panels, which look for mutations in several different genes at the same time.
You and your family members are more likely to have Lynch syndrome if your family has a strong history of colorectal cancer. Family members who inherit Lynch syndrome usually share the same mutation. If one of your family members has a known Lynch syndrome gene mutation, other family members who get genetic testing should be checked for that mutation.
If you are concerned that you could have Lynch syndrome, or another mutation related to colorectal cancer, the first step is to collect your family health history of colorectal cancer and share this information with your doctor.