What is Lynch Syndrome?

What is Lynch Syndrome?

Lynch syndrome (previously known as HNPCC) is an inherited genetic mutation which gives people an increased chance of developing certain cancers across their lifetime, often at a younger age than the general population (i.e. before 50 years of age). 

These cancers include, but are not limited to:

  • Bowel cancer*
  • Endometrial cancer (lining of the uterus)*
  • Ovarian cancer
  • Stomach cancer
  • Hepatobiliary cancer (liver/gallbladder)

  • Urinary tract cancer
  • Kidney cancer
  • Pancreatic cancer
  • Brain cancer
  • Skin (sebaceous adenoma, sebaceous epithelioma, or sebaceous carcinoma and keratoacanthoma)
  • Small bowel cancer

*Most common cancers associated with Lynch syndrome.

If you have been diagnosed with Lynch syndrome or are considering being tested, it is important that both you and your doctor are aware of your family’s history of these cancers. Recent studies suggest there may be an increased chance of developing breast and prostate cancer so you should also be mindful of your family’s history of these cancer types.

The Genes Responsible

Lynch syndrome is caused by a mutation in one of the body’s mismatch repair (MMR) genes. These genes are: MLH1, MSH2, MSH6, and PMS2.

Your family may be affected by a mutation in any one of these genes. Normally, a person will inherit two working copies of these genes, one from their mother and one from their father. When working correctly, these genes work by repairing the mistakes that can occur when DNA is copied in preparation for cell division. In Lynch syndrome however, a person inherits one working copy and one non-working copy of one of these genes. When non-working MMR genes fail to repair these mistakes in DNA, errors accumulate, which may lead to uncontrolled growth of cells and eventually, cancer.

How is it passed down in families?

Lynch syndrome is inherited, which means that a parent with Lynch syndrome has a 50% (1 in 2) chance of passing the condition on to their children. Men and women have an equal chance of inheriting Lynch syndrome.

Lynch syndrome can not skip a generation so if your children do not inherit Lynch syndrome, your grandchildren will not be affected either. 


How to know if your family has Lynch syndrome?

A general guide to identifying families who may carry Lynch syndrome is provided by the 3, 2, 1 rule. 

A strong family history of cancer, or cancers, occurring at a younger than normal age does not necessarily mean that your family has Lynch syndrome. But it does mean that you should speak to your doctor to find out if genetic counselling and testing would be suitable for you.


3 or more family members (including you) have been diagnosed with a Lynch syndrome associated cancer


2 consecutive generations or more are affected


1 affected family member is diagnosed with a Lynch syndrome associated cancer before 50 years of age

What Now?


Thinking about getting tested

There are a number of reasons why you might be considering genetic testing for Lynch syndrome. These include, but are not limited to:

– A family member has been diagnosed with Lynch syndrome

– You have recently been diagnosed with cancer at a younger than normal age for that cancer type or with a cancer that showed some features of Lynch syndrome

– Your family history suggests Lynch syndrome

Visit our Getting Tested page to learn about the process and where to begin.

Getting Tested


I have Lynch syndrome

Having Lynch syndrome does not necessarily mean that you will get cancer in your lifetime but it does mean that you should speak with your doctor to develop your surveillance plan.

Your genetic counsellor or geneticist should have told you the routine tests (surveillance plan) you will need to follow and how often you would need to do so. These tests are important as they have the ability to detect tumours before they become cancerous or detect cancer at an early stage before it becomes life threatening.

For example, colonoscopies can find polyps in the bowel and they can be removed before they turn into a bowel cancer*.

Visit our managing the risk page to find out more.

*Note: Not all polyps will progress to bowel cancer.

Managing the Risk


How can I help?

We appreciate your desire to help support Lynch Syndrome Australia.

There are many ways that you can show your support to the many families affected by Lynch syndrome across the nation. You could host a fundraiser, raise awareness in your own community about the importance of knowing your cancer family history or even make a donation today.