Lynch syndrome (LS)

Lynch syndrome (LS) is a condition that can run in families. LS is also known as hereditary non-polyposis colorectal cancer (HNPCC). It is caused by an alteration in a gene called a mismatch repair gene.

LS doesn’t cause any symptoms. But people with LS have an increased risk of developing bowel cancer, womb cancer and some other cancers. If your family has a history of developing these cancers when they are under 50 years old, it is possible they have the altered gene that causes LS.

If you are worried about your family history, talk to your GP. They may refer you for genetic testing or recommend you have regular screening for some cancers. If you have LS, it is important to be aware of the signs and symptoms of bowel and womb cancer. If you develop any symptoms, you will need to get them checked by a doctor.

Having LS, and knowing you are at increased risk of cancer, can be difficult. There is lots of support available for you.

What is Lynch syndrome?

Lynch syndrome (LS) is a rare condition that runs in families. Conditions that run in families are known as familial or hereditary.

LS is also known as hereditary non-polyposis colorectal cancer (HNPCC). But people with HNPCC have an increased risk of some other cancers, not just colorectal cancer, so health professionals usually call the condition Lynch syndrome. It is named after the doctor who discovered it.

LS is the most common cause of hereditary bowel cancer. However, fewer than 5 in 100 (5%) of all bowel cancers are linked to LS.

People with LS also have an increased risk of developing other cancers. In women, there is a higher risk of womb (endometrial) and ovarian cancers. Other cancers that can occur in people with LS include:

  • stomach
  • pancreas
  • small bowel
  • ureter and renal pelvis cancers.

Knowing about the risk and having regular screening may help prevent some cancers. It may also help other cancers be found in the early stages, when they are more likely to be curable.

How Lynch syndrome is inherited

Our genes carry the information that is passed on (inherited) from our parents. Genes determine things like the colour of our eyes. And they affect the way our bodies grow, work and look.

LS is caused by an alteration in a gene called a mismatch repair gene. Mismatch repair genes normally help stop us getting cancer.

LS may be suspected if a family has close blood relatives who have developed bowel, womb and ovarian cancer over several generations. Close relatives are parents, children, sisters and brothers. Their cancers may have been caused because they have inherited an altered copy of one of the mismatch repair genes.

Three of the mismatch repair genes are responsible for most cases of LS. These genes are called MLH1, MSH2 and MSH6. Another mismatch repair gene called PMS2 is also sometimes tested for. If a person inherits an altered copy of one of these genes, they have a higher risk of developing cancer.

We have two copies of every gene – one from each of our parents. If someone has LS, it means they have one healthy gene and one gene that is altered. If that person has a child, there is a 1 in 2 (50%) chance that they will pass on the altered gene. This is because only one copy of a gene is passed on from each parent.

LS is more likely if there are lots of cases of bowel and womb cancer on one side of the family that were diagnosed at an early age. However, not everyone with LS has a family history of cancer. This is because some people may be the first in their family to get it.

LS may be suspected if:

  • at least two relatives on the same side of the family have had bowel cancer
  • a family member developed bowel cancer at a young age (under 50)
  • there are cases of bowel and womb cancer on the same side of the family
  • three or more relatives on the same side of the family have had one LS-type cancer (not necessarily the same kind of cancer).

If you're worried about cancer in your family, speak to your GP. They can refer you to a family cancer clinic.

Signs and symptoms of Lynch syndrome

LS 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 LS 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 is usually a history of these cancers in the family.

Symptoms of bowel cancer

Bowel cancer that doesn't run in families usually develops in people over 50. But for people with LS, bowel cancer usually develops between the ages of 40 and 50 or younger.

Being aware of your normal bowel habits is important, particularly if you have or think you may have LS.

If you have any of the following symptoms, it's important to get them checked out by a doctor:

  • Blood on or in your stools (poo).
  • Diarrhoea, constipation or another change to your bowel habit that lasts longer than six weeks and has no obvious reason. 
  • Unexplained weight loss.
  • Pain in the tummy or back passage.
  • A feeling of not having emptied your bowel properly after you go to the toilet.

Symptoms of womb cancer

It's important for women who have or think they may have LS to be aware of the symptoms of womb cancer. Any of the following symptoms should be checked out by a doctor:

  • Abnormal vaginal bleeding or discharge. This could be bleeding between periods, having heavier periods or bleeding after the menopause.
  • Pain in the lower abdomen (tummy), back or legs.
  • Pain or discomfort during sex.

All of these symptoms can be caused by conditions other than cancer, but it's important to get them checked out by your doctor.

Diagnosing Lynch syndrome

A genetic test can sometimes show if someone has LS. If a person has a suspected LS-type cancer, they can have a genetic test done on a tissue sample (biopsy) taken from the cancer. This test will only be done with their permission.

It may be that the only people in your family who have had a suspected LS-type cancer in the last few years have died. Hospitals usually keep tissue samples for several years, so they can often supply a sample for the genetic test. This can only happen if a close living relative has given permission.

If this genetic test is positive, it shows that the person has or had LS. This will affect how often their relatives should have regular bowel screening. If possible, the person who has had cancer is asked to give a blood sample to test for the LS gene. If the altered LS gene is found, close relatives who have not had cancer can choose to have the blood test. This would find out if they have inherited the altered LS gene.

Genetic testing

Genetic testing can only be done if a person is willing to have it. It is important to be aware that not everyone in a family will have the same feelings about genetic testing. These differences can sometimes cause upset in families.

Before genetic testing, a person will have counselling to help them understand the possible results and what it may mean for them and their family.

Sometimes the altered gene can't be found in the person with the LS-type cancer. This could be because they don’t have LS. Or it could be because there's an alteration in a different gene that research hasn't yet identified. If an altered gene is not found, other family members can't be tested. However, based on their family history, they can still have regular bowel tests, and women can sometimes also have womb checks. These tests aim to manage people’s increased cancer risk.

What the test results mean

If you have already had an LS-type cancer and you have the altered gene

You may need regular bowel screening. Women may also be screened for womb or ovarian cancer. The kind of screening you have depends on the type of surgery, if any, you have had.

If you have LS in your family and you have inherited the altered gene

You will be advised to have regular screening to reduce your risk of LS-type cancers. If you have children, they will have a 1 in 2 (50%) risk of inheriting the altered gene. Your close relatives who have not had cancer may also have inherited the altered gene.

If you have LS in your family and have not inherited the altered gene

Your cancer risk is the same as anyone else's. You won't need screening and your children will not have an increased risk of LS-type cancers.

Screening to reduce your risk of cancer

If you know your risk of cancer is increased, you can have regular tests called screening. Bowel and womb cancers can be curable when they are found early. And if bowel polyps are removed, they cannot turn into cancers. If someone has inherited the altered gene, they will usually be advised to have regular bowel screening from a young age – normally 25. Women in their 30s may also be referred to a gynaecologist to discuss how to manage their risk of womb cancer.

If the altered gene isn’t found in a relative with LS-type cancer, it's still important for you to have screening, as you may still be at risk of developing cancer. This is also true if you decide not to have genetic testing, or if you can’t have it because a relative with LS-type cancer doesn’t want a test.

Screening for bowel cancer

Bowel screening involves a test called a colonoscopy. This is where a thin, flexible tube is used to examine the bowel and diagnose any pre-cancerous polyps (small growths) or early cancers early on when they are curable. Samples of tissue (biopsies) may also be taken.

The colonoscopy is usually done in the hospital outpatient department and takes about an hour. Your bowel has to be completely empty for the test. This means you'll have to follow a special diet for a few days beforehand. On the day before your colonoscopy, you'll be asked to take medicine (a laxative) to empty your bowel. Your hospital will give you instructions about preparing for a colonoscopy.

Just before the test, you will be given a drug to make you feel more relaxed (a sedative). This may be given as an injection into a vein (intravenously). Once you're lying comfortably on your side, the doctor or nurse will gently pass a flexible tube (a colonoscope) into your back passage (rectum). A colonoscope is a long, thin, flexible tube that has a tiny light and a camera on the end of it. It can easily pass around curves, so the doctor or nurse can examine most of the large bowel. During the test, they may take photographs and samples of tissue. They can also remove any polyps before they develop into a cancer.

After the test, you will need somebody to go home with you. They need to stay with you for 24 hours until the effects of the sedative wear off. It is important not to drive during this time. Colonoscopies are usually repeated every 1 to 2 years. If you’ve had a polyp removed, you may be asked to have another colonoscopy the following year.

Taking aspirin to prevent bowel cancer

It has been suggested that taking aspirin regularly may help prevent bowel cancer in people who have the LS gene alteration. However, we don’t yet know what the most helpful dose is, and aspirin can have harmful side effects. More research is needed into the possible benefits of aspirin for people with LS. CAPP3 is a current research study that is looking at what the best dose of aspirin is for preventing cancer in people with LS. If you have the altered gene and you want to know more about taking aspirin, your doctor can advise you.

Screening for womb cancer

We don't know whether womb screening in women with LS is helpful. Some women may be offered it, but it's not available everywhere.

Screening can be done using a procedure called a hysteroscopy, where a thin, flexible tube with a light at the end is used to look inside the womb. It can also be done using a vaginal ultrasound, where a small device that makes soundwaves is put into the vagina. The soundwaves are then converted into a picture by a computer. Your doctor or nurse will explain which test you will have.

Screening for ovarian cancer

If you have LS, your risk of developing ovarian cancer is much lower than your risk of developing bowel or womb cancer.

There is currently no standard screening test for ovarian cancer. Some women may be offered it, or they may have had it done as part of a research trial. More research is needed to see what screening may be useful for women at risk of familial ovarian cancer.

Where it is offered, ovarian screening can involve a blood test, a vaginal ultrasound, or both. The blood test checks the levels of a protein called CA125.

Treating Lynch syndrome-type cancers

If you develop bowel cancer, it is likely to be picked up early through having regular colonoscopies. Any LS-type cancer is treated in the standard way for that type of cancer.

Treating bowel cancer usually involves surgery to remove the cancer. Further treatment with chemotherapy may be needed, depending on the stage of the cancer.

Treating womb cancer usually involves removing the womb (hysterectomy) and the ovaries. Radiotherapy and chemotherapy may also be given.

Your feelings

It can be difficult to cope with knowing that you have LS, or that you are at risk of it. The uncertainty of not knowing whether you will develop cancer isn't easy to deal with, but it's important to remember that some cancers can be found early and cured.

You may have concerns about genetic testing, screening or whether you should have risk-reducing surgery. It is important to talk these concerns over with your doctor and nurse. They will be happy to answer any questions you have.

You may have many different emotions, including anxiety and fear. These are all normal. They are part of the process many people go through when trying to come to terms with their condition.

Many people find it helpful to talk things over with their doctor or nurse. Close friends and family members can also offer support.

Useful organisations

We have a list of organisations that may be able to offer you support and information. Our database of useful organisations lists organisations that provide both practical and emotional support, including information on health, benefits and financial help.