Lynch syndrome

Father and son

What is Lynch syndrome?

Lynch syndrome (LS) is a genetic condition that is passed on between families (inherited). A syndrome is a group of signs and symptoms that occur together and point to a particular condition.

Most people who have Lynch syndrome (LS) are well and don't know they have LS. However, someone with LS is more at risk of developing certain types of cancer than other people of a similar age.

Colorectal (bowel) cancer is the cancer most associated with Lynch syndrome. Lynch syndrome was also previously known, and is sometimes still called, hereditary nonpolyposis colorectal cancer (HNPCC). ‘Nonpolyposis’ means that bowel cancer can occur when only a small number of polyps are present (or polyps are not present at all). The name was likely given to differentiate it from another type of inherited syndrome – familial adenomatous polyposis (FAP) – where thousands of polyps develop in the bowel.

What is a polyp?

A polyp is an abnormal growth of tissue in the lining of your bowel. People with Lynch syndrome may develop polyps, which can vary in size. Colon polyps are very common and most are harmless. But if they are left untreated, they can lead to cancer. Adenomas are benign (not cancerous) growths and the most common type of polyp in Lynch syndrome.

Cancers associated with Lynch syndrome

Some colorectal (bowel) cancers are hereditary. About 5 people out of every 100 diagnosed with bowel cancer have Lynch syndrome. Other cancers linked to Lynch syndrome include:

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Be aware of gene changes and cancer in your family and take part in screening to reduce your risk of cancer.

How is Lynch syndrome inherited?

Genes are found in all the cells that make up your body. They hold your genetic material (DNA) and are responsible for many things like the colour of your eyes or how tall you are. They also contain information that tells your body how to work and grow. Genes are passed on from your parents, which means that you inherit them.

We all have genes that are responsible for protecting us from abnormal cell growth. In Lynch syndrome some of these cancer-fighting genes are altered and do not work properly. This means that their cancer protection mechanism is not working fully, and so people with Lynch syndrome have less protection against cancer.

In Lynch Syndrome some of these cancer fighting genes are altered and do not work properly. This means that their cancer protection mechanism is not working at 100%, and so people with Lynch syndrome have less protection against cancer.

Who might be at risk of having Lynch syndrome?

Doctors have put guidelines together to help them find out who may have Lynch syndrome and which families may be at risk. These are called the Bethesda/Amsterdam criteria. Doctors can find out who is at high risk and send them for more tests, if needed. Those at high risk are:

  • If you have three family members with colorectal cancer: One must be a first-degree relative of the other two; and two generations in a row of the same family must be affected by cancer; and one of these relatives must be diagnosed with cancer before the age of 50. Note: A first-degree relative is your parent, brother or sister, or your child.
  •  If you have two Lynch syndrome-related cancers: These cancers include colorectal, ovarian, womb, ureter or kidney cancer.
  •  If you have colorectal cancer and a first-degree relative with colorectal cancer and/or a Lynch syndrome-related cancer: These cancers include ovarian, womb, ureter or kidney and/or colorectal adenoma; with one of these cancers diagnosed under the age of 45 years and the adenoma under the age of 40 years.

Note: Colorectal adenoma is a benign (not cancerous) growth in the glands of the bowel. Adenomas can develop into colorectal cancer over time.


What should I do if I have a strong family history?

If you are concerned about your family history, it is important to discuss these concerns with your GP. They may then refer you to a family risk-assessment clinic.

At this clinic, your family history will be looked at more closely and a family tree done. This family tree is known as a pedigree.

If Lynch syndrome is suspected, a test is done on the tumour of a family member with cancer. This happens only with the person’s consent. Based on this, you may be referred for genetic testing.

What is genetic testing?

A number of genetic changes may lead to Lynch syndrome. This is unlike other conditions, for example, familial adenomatous polyposis (FAP), where a single gene alteration is the cause of the condition. Some of these alterations may not yet be found. As a result, genetic testing is only possible if an alteration has been found in a family member.

Genetic testing involves taking a blood sample. This is sent to a special laboratory to try and find the particular fault in the gene. It may be many weeks before you get the results of these tests. If you need genetic testing, you will be given information and counselling before the test takes place as well as after you get the results. At present, genetic testing is only suitable for people with a strong family history.

Who can be tested?

There are two stages to genetic testing within a family.

  1. A family member with cancer gives their consent to have their tumour tested. Based on this result, they may be offered genetic testing to find the fault on the gene.
  2. If a genetic alteration is found in that family member, then genetic testing can be offered to other members of the family.

It is up to each family member to decide if they wish to be tested to find out if they carry the genetic fault.

What is the referral process and where is testing done?

In most cases, your GP or oncologist will refer you to genetic testing services – most often in the National Centre for Medical Genetics at Children's Health Ireland, Crumlin, Dublin.

This is the main genetics clinic in Ireland, but it has outreach clinics in University Hospital Galway, University Hospital Limerick and Cork University Hospital.

There is also a genetics clinic at St James’s Hospital and in the Mater Hospital in Dublin.

There are also private clinics offering genetic counselling and testing services. You will still need to be referred to these clinics.

What happens if a family member has Lynch syndrome?

If either of your parents has Lynch syndrome, you have a 1 in 2 chance (50 per cent) of inheriting the gene. In this case, you will be invited to go for genetic testing.

If you inherit a gene, it does not mean you will get cancer – but it increases your risk of cancer. Your chance of getting colorectal (bowel) cancer in your lifetime would be 4 in 5 (80 per cent). Your lifetime risk of getting womb cancer would be 3 in 5 (60 per cent) and a 1 in 10 chance (10 per cent) of getting ovarian cancer.

Which gene change can cause which cancer?

The main genes involved in Lynch syndrome are MLH1, MSH2, MSH6, PMS2 and EpCAM. An alteration in any of these genes is associated with an increased risk of developing certain cancers. The precise cancer is usually determined by which of these genes has been linked to cancer in your family.

What happens if I have a gene for Lynch syndrome?

If you have a diagnosis of Lynch syndrome, it could be worrying to know that you have a higher likelihood of developing cancer. On the other hand, you are armed with knowledge and an enhanced screening programme that will help you prevent these cancer types or help to diagnose and treat them early.

Screening may include:

  • Colon (large bowel) screening.
  • Womb and ovarian screening.
  • Stomach screening.

Colon (large bowel) screening
Screening involves a test called a colonoscopy, where a camera is used to examine the bowel for any abnormal changes. You will be advised to have this every 1-2 years from the age of 25 years onwards. It is also important to be aware of any new bowel symptoms, including bleeding from your back passage, weight loss or a change in bowel habit. If you develop any of these symptoms in between screening, have them checked by your doctor.

Womb and ovarian screening
Screening involves having pelvic exams, ultrasounds and blood tests every 2-3 years, at least. Screening should start from the age of 35 years. You should also be aware of the symptoms of womb problems. These include heavy periods, bleeding between periods, bleeding after sex and bleeding after the menopause. If you develop any of these symptoms between screenings, visit your doctor to have them checked.

Some women with a high risk of womb or ovarian cancer may decide to have risk-reducing surgery. This involves removing the womb and ovaries. You can discuss this with your doctor or genetics team.

See more on womb cancer and on ovarian cancer.

Early menopause
If you have not been through menopause and decide to have risk-reducing surgery – removing your womb and ovaries – you can expect to go into menopause.

Speak to your GP about early menopause supports and hormone replacement therapy (HRT). Read more about managing menopausal symptoms.

Stomach screening
You will have a scope (camera) test called a gastroscopy to screen for changes in the stomach. For people with Lynch syndrome, it is recommended that screening be done every 2 years from the age of 25–30 years.

It is also important to be aware of new symptoms including weight loss, feeling sick, loss of appetite, bloating or difficulty in swallowing. If you get any of these symptoms between screening, have them checked out by your doctor.

More information on stomach cancer.

Telling family if a genetic change is found

If a genetic change is found, this means that you are at a higher risk than the general population of developing cancer.

Telling your family about your Lynch syndrome diagnosis can be a difficult task. The genetics team will be able to advise you about this. Telling your family can help them to make decisions about screening and testing. When you have genetic counselling you will discuss the best way to inform relatives. They can give you letters and scripts.

For more information about talking to family, and about genes and inherited cancers, download our factsheet Cancer and Genes or talk to a cancer nurse on our Support Line 1800 200 700.

What happens if I do not inherit the gene?

If you have not inherited an abnormal gene, you will not need any special screening. This is because your risk of getting cancer is the same as the rest of the population. But you should continue to be aware of any changes in your body and report any new symptoms to your doctor. For bowel cancer, these can include bleeding from the back passage, weight loss or a change in bowel habit.

It is also best to eat a healthy diet, which is low in fat and high in fibre, stay a healthy weight, stick to the low-risk alcohol guidelines and get regular exercise to reduce your risk of getting cancer.

For more information

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