Lynch syndrome


Lynch Syndrome (previously known as HNPCC - Hereditary Non-Polyposis Colon Cancer) is an autosomal dominant cancer predisposition syndrome characterized by colorectal adenocarcinoma without (Lynch Syndrome type I) or with (Lynch Syndrome type II) extra colonic cancers (including ovarian, endometrium, small bowel, stomach, ureter or renal pelvis and others). Lynch syndrome is the most common cause of hereditary bowel cancer. However, fewer than 5 in 100 (5%) of all bowel cancers are linked to Lynch Syndrome.  


Lynch Syndrome itself doesn't cause any symptoms. It's an inherited syndrome that means a person has a higher risk of developing bowel and womb cancer. 

Sometimes the first sign that a person has Lynch Syndrome is when the symptoms of bowel or womb cancer develop. This generally happens at a younger age than for people whose cancers aren't due to an inherited gene alteration. With LS, there's usually a history of these cancers in the family.  


Lynch Syndrome is caused by inactivating mutations in genes of the DNA mismatch repair system (MMR genes). MMR gene mutations result in failure to repair errors during DNA replication. Cancer is likely to develop when unrepaired replication errors inactivate genes including tumour suppressors. The MMR genes MLH1 and MSH2 account for approximately 80-90% of Lynch Syndrome. Mutations in some other genes (MSH6, TGFBR2, PMS1, MSH6) are also identified to cause Lynch syndrome .


Frequent cancer screening and preventive surgery are the only ways to reduce the risk of cancer in people with Lynch syndrome. No other measures have been proved to reduce your risk. Researchers are studying other ways to reduce cancer risk. One study found people with Lynch syndrome who took aspirin for two years reduced their risk of colon cancer and other Lynch-related cancers. Discuss the benefits and risks of taking aspirin with your doctor.

Take control of your health by trying to:

  • Eat a healthy diet full of fruits and vegetables.

  • Exercise regularly.

  • Maintain a healthy weight.

  • Stop smoking.


It's sometimes possible to find out if someone has LS by doing a genetic test. If a person has a suspected LS-type cancer, a test may be done on a tissue sample taken from the cancer of a relative who has had cancer recently, or in the last few years. Hospitals usually keep tumour samples for several years and can often supply tissue for this kind of testing. The test is done with the consent of the person providing the tissue sample. If this genetic test is positive, the relative who has had cancer is asked for permission to take a blood sample. If the altered LS gene is found, closely related family members (not affected by cancer) can choose to be tested to see if they have inherited it. 


Coloscopy screening at 3 year intervals more than halves the risk of colorectal cancer, prevents colorectal cancer deaths, and decreases overall mortality by about 65% in HNPCC families.