Lynch syndrome: inherited bowel and womb cancer risk explained

Genes are coded messages that tell cells how to grow and work. Guy's and St Thomas' explains that we inherit one copy of each gene from each parent, and that the genes related to Lynch syndrome usually protect against cancer by controlling cell growth. If someone inherits a fault (mutation) in one copy of a Lynch-related gene they are more likely to develop Lynch-related cancers, and more likely to get non-cancerous growths such as bowel polyps and skin changes.

NHS England adds that the syndrome does not directly cause cancer. The genetic changes allow more abnormal cells to develop, which then multiply and increase the risk of cancers such as bowel, prostate and endometrial cancer. Many people with Lynch syndrome never develop cancer.

Lynch syndrome is a gene change, so it is usually not noticed until a cancer or polyp appears, or until a family member or a test identifies it. The Eve Appeal says 95% of people with Lynch syndrome do not know they have it. Because of this, the symptoms that matter are those of the cancers it raises the risk of, and surveillance does not replace reporting symptoms.

The NHS lists the symptoms of bowel cancer as changes in your poo that are not usual for you, needing to poo more or less often, blood in your poo, bleeding from your bottom, feeling that you need to poo even when you have just been, tummy pain, a lump in your tummy, bloating, losing weight without trying, and tiredness or breathlessness from anaemia.

The NHS lists the main symptoms of womb cancer as bleeding or spotting from the vagina after the menopause, heavy periods that are unusual for you, bleeding between periods and a change in vaginal discharge. It asks you to tell the GP if you or your family have a history of cancer or Lynch syndrome.

Guy's and St Thomas' says people with Lynch syndrome are more likely to develop cancer at a younger age and may get cancer more than once. For context, it says about 10 to 15 out of 100 bowel cancers happen when someone has inherited an increased risk, and about 2 out of 100 bowel cancers are caused by Lynch syndrome.

Genes come in pairs. Guy's and St Thomas' says that if someone has a mutation in one of their copies of a Lynch-related gene, they have a 1 in 2 (50%) chance of passing it to each child, regardless of the gender of the parent or the child.

This is why a diagnosis matters for relatives. NHS England says relatives who receive a diagnosis can be referred to genetic services to discuss regular testing options to catch cancers early, and preventive options such as taking aspirin or risk-reducing surgery. The Eve Appeal advises that if you have a family history of bowel or womb cancer you should speak to your GP and ask for a referral to your local genetics centre.

NHS England says the NHS can now identify the condition through a simple blood test, which goes through a regional genomic laboratory hub, is sequenced and is sent back to the referring clinician. It also reports a dedicated genetic testing programme in which, on average, 94% of people diagnosed with bowel and endometrial cancer between 2021 and 2023 received the initial test to check for Lynch syndrome, up from 47% in 2019.

Guy's and St Thomas' describes genetic testing to investigate whether Lynch syndrome runs in a family, and predictive testing in relatives. It says that in some families no genetic testing is possible, but bowel screening can still be arranged and options for reducing womb and ovarian cancer risk can be discussed.

Deciding to be tested is personal and can be complex. The Trust suggests considering timing, the psychological impact of knowing, how you would share the result with family, how you cope with difficult news, possible effects on employment or insurance, and what you would do about the risks. If you decide against testing you may still be eligible for regular bowel screening.

In February 2024 NHS England announced that people with Lynch syndrome are invited for bowel surveillance every two years through the NHS Bowel Cancer Screening Programme, where they are seen by a specialist team and assessed for a colonoscopy, which checks for polyps and signs of bowel cancer. It says that out of 100 people with Lynch syndrome, screening prevents between 40 and 60 from getting bowel cancer, and that around 10,000 people in England were on the Lynch syndrome register at that time.

Other options NHS England mentions are taking aspirin and risk-reducing surgery, which can be discussed with genetic services. The right plan for womb and ovarian cancer risk is individual and made with a specialist team.

See a GP if you notice any bowel cancer symptoms or abnormal vaginal bleeding, even if you are in a surveillance programme. The NHS says to ask for an urgent GP appointment or call NHS 111 if your poo is black or dark red or you have bloody diarrhoea.

The NHS says to call 999 or go to A&E if you are bleeding non-stop from your bottom, or there is a lot of blood or large blood clots when you poo.

On the NHS, Lynch syndrome is usually identified through tumour testing after a bowel or womb cancer diagnosis, or through a referral to a regional clinical genetics service because of a family history. Once diagnosed, surveillance colonoscopy is arranged through the national bowel screening programme in England.

Private genetic counselling and testing services exist, but results need to be linked into an NHS surveillance programme for ongoing care. If you consider a private test, ask who will interpret the result, whether relatives can be offered testing and how surveillance will be organised.