Lynch syndrome

Lynch syndrome (LS) is a condition that can run in families. It is also known as hereditary non-polyposis colorectal cancer (HNPCC). LS doesn’t cause any symptoms itself. But people with LS have an increased risk of developing bowel cancer, cancer of the womb and some other cancers. If your family has a history of developing these cancers at a young age (under 50), it is possible that you 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 if necessary, or recommend you have regular screening for bowel or other cancers. If you have LS, it’s important to be aware of the signs and symptoms of bowel and womb cancer. If you develop any, you’ll need to get them checked out by a doctor.

Occasionally, if a person’s risk is seen as very high, doctors may suggest having surgery to remove the large bowel or the womb. This is to reduce the risk of cancer.

Having Lynch syndrome, 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). Because people with HNPCC have an increased risk of some other cancers, and not just colorectal cancer, health professionals usually call the condition Lynch syndrome, named after the doctor who discovered it.

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 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 risk and having regular screening may help prevent some cancers. It may also help others to be found in the early stages, when they're more likely to be curable.

How Lynch syndrome is inherited

Our genes carry the information that's passed on (inherited) from our parents. Genes determine things like the colour of our eyes and 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. They may have inherited an altered copy of one of the mismatch repair genes.

Three of the mismatch repair genes are responsible for most cases of Lynch syndrome. These genes are called MLH1, MSH2, and MSH6. Another mismatch repair gene called PMS2 is also sometimes tested for in cases of Lynch syndrome. 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 but also one that's 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 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 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's 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 occurs between the ages of 40–50 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 the stools (bowel motion)

diarrhoea or constipation for no obvious reason (a change to your normal bowel habits that lasts longer than six weeks)

unexplained weight loss

pain in the tummy or back passage

a feeling of not having emptied the bowel properly after a bowel motion.

Symptoms of womb cancer

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

  • Abnormal vaginal bleeding (between periods, heavier periods or bleeding after the menopause).
  • Pain in the lower abdomen (tummy), back or legs.
  • Pain or discomfort during sexual intercourse.

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

How Lynch syndrome is diagnosed

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.

Genetic testing

Genetic testing can only be carried out if a person is willing to have it. It’s important to be aware that not everyone in a family will have the same feelings about genetic testing. And 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 these results 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 it's not LS, or because there's an alteration in the gene that research hasn't yet identified. If no gene change is 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. The aim of these tests is to reduce people’s cancer risk.

What the test results mean:

  • If you've already had an LS-type cancer and 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 will depend on the type of surgery (if any) you have already had.
  • If you have LS in your family and have inherited the altered gene, you'll 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

Knowing your risk of cancer means you can have regular tests (screening). Bowel cancers and womb cancers can be curable when they're found early.

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

Bowel screening

A test called a colonoscopy is used to examine the bowel and diagnose any cancers early on when they're curable.

The test 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 most of the large bowel can be examined. During the test, photographs and samples of tissue (biopsies) may be taken. Any polyps (small growths) can also be removed before they develop into a cancer.

After the test, you will need somebody to go home with you and 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 1–2 years. If you’ve had a polyp removed, you may be asked to have another colonoscopy the following year.


It has been suggested that a regular dose of aspirin 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. If you have the altered gene and you want to know more about aspirin, your doctor can advise you.

Womb screening

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

The womb can be screened using a procedure called a hysteroscopy or by using a vaginal ultrasound. Your doctor or nurse will explain which test you will have.

During a hysteroscopy, a thin, flexible tube with a light at the end is used to look inside the womb.

A vaginal ultrasound scan involves putting a small device that makes soundwaves into the vagina. The sound waves are then converted into a picture by a computer.

Ovarian screening

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.

Ovarian screening can involve a blood test, a vaginal ultrasound, or both. The blood test checks the levels of a protein called CA125.


If you develop bowel cancer, it's 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.

Treatment for bowel cancer will usually involve surgery to remove the cancer. Further treatment with chemotherapy may be needed, depending on the stage of the cancer.

Treatment for womb cancer will usually involve removing the womb (hysterectomy) and the ovaries. Radiotherapy and chemotherapy may also be given.

Risk-reducing surgery

Occasionally with LS, it's recommended that the whole of the large bowel is removed. This is known as risk-reducing surgery. It's usually only recommended when the risk of developing cancer is thought to be very high, or if a person with LS develops more than one bowel cancer.

Some women who have already had children may choose to have their womb and ovaries removed. This is to reduce their risk of developing womb and ovarian cancer.

Your feelings

Knowing that you have Lynch syndrome or are at risk of it can be very difficult to cope with. 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's important to talk these concerns over with the doctors and nurses caring for you. They'll be happy to answer any questions you have.

You may have many different emotions, including anxiety and fear. These are all normal reactions and are part of the process many people go through in 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.

Back to Genetic testing and counselling

Inherited cancers

If a cancer occurs more often in a family than in the general population, some people in the family may have inherited a cancer susceptibility gene.

Genetic counselling

A genetic consultation is a discussion with a person trained in genetics. They will advise you on your risk of developing cancer.

Genetic testing

You will only be offered genetic testing if your family history suggests you may have inherited an identified faulty gene.

OPERA tool

OPERA is an online information tool for people concerned about their inherited risk of breast and/or ovarian cancer.