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The MSH2 gene: what it does and why it matters | CION Cancer Clinics
MSH2 is one of the genes that proofreads your DNA each time a cell copies itself. When one copy is faulty from birth, errors can build up faster, and that raises the risk of bowel, womb, urinary tract and some other cancers. It is one of the causes of Lynch syndrome. This page explains what the gene normally does, what goes wrong, and what a fault means for your family. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- What does the MSH2 gene actually do?
- Which cancers are linked to an MSH2 fault?
- How does a faulty MSH2 gene lead to cancer?
- What do the words on an MSH2 report mean?
- How does MSH2 differ from the other Lynch genes?
- What this page cannot tell you
- Four things families say about MSH2, and what is true
- Common questions about the MSH2 gene
The short answer
What does the MSH2 gene actually do?
MSH2 is a proofreading gene. Every time a cell divides, it copies its DNA, and small spelling mistakes creep in. The MSH2 protein spots those mistakes and flags them for repair, working closely with a partner protein called MSH6. Doctors call this job mismatch repair.
What happens when one copy is faulty
You carry two copies of MSH2, one from each parent. Someone who inherits a fault has only one working copy in every cell of the body. One copy is still enough, so nothing goes wrong at first. If that last working copy is damaged in a single cell, the proofreader in that cell is gone. Copying errors then build up quickly, and a cancer can form faster than it usually would.
Why doctors pay attention to it
An inherited MSH2 fault is one of the main causes of Lynch syndrome, the most common inherited cause of bowel and womb cancer. It raises the risk of several other cancers too, including some in the urinary tract. Knowing about the fault means checks can start years before they would for anyone else, and relatives can be tested for the same fault.
An MSH2 fault is a statement about risk. It is not a diagnosis of cancer.Where the risk sits
Which cancers are linked to an MSH2 fault?
The risk is spread across several organs. Some are common, and some are rare even in carriers.
Bowel
Bowel cancer is the best known risk. It tends to appear at a younger age than in the general population, often on the right side of the colon. Regular colonoscopy can remove growths before they turn into cancer.
Womb and ovary
For women, the risk of womb cancer is as high as the bowel risk, and sometimes higher. Ovarian cancer risk is raised as well.
Worth knowing
- Bleeding between periods
- Any bleeding after the menopause
Urinary tract
MSH2 stands out among the Lynch genes for a raised risk of cancer in the tubes that drain the kidneys and in the bladder. Blood in the urine is the sign to report.
Less common sites
Stomach, small bowel, pancreas, bile ducts and brain are all on the list. So are small oily skin growths called sebaceous tumours. Each of these is uncommon, and most carriers never develop them.
Not sure whether this applies to you?
Ask an oncologistFrom fault to tumour
How does a faulty MSH2 gene lead to cancer?
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Every cell starts with one working copy
A carrier is born with one faulty and one working copy of MSH2. The working copy does the whole job, so repair carries on as normal.
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The working copy is lost in one cell
Over years, ordinary wear and chance damage can knock out the second copy in a single cell, often in the lining of the bowel or womb.
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Copying errors stop being fixed
Without MSH2, that cell cannot correct its mistakes. Errors pile up with every division, especially in short repeated stretches of DNA.
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Errors land in growth genes
Sooner or later a mistake hits a gene that controls growth. The cell begins to divide when it should not, first as a polyp and later, sometimes, as a cancer.
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The tumour carries a fingerprint
These tumours usually show high instability on testing and are missing the MSH2 and MSH6 proteins on staining. That fingerprint is often how an MSH2 family is first found.
On your report
What do the words on an MSH2 report mean?
- Mismatch repair
- The cell's spell-checker for DNA. MSH2 is one of four genes that run it, with MLH1, MSH6 and PMS2.
- Lynch syndrome
- The inherited condition caused by a fault in any of those spell-checker genes, or by an EPCAM deletion.
- Microsatellite instability
- A tumour result showing that repeated DNA stretches have changed length. It suggests the spell-checker has failed.
- Immunohistochemistry
- A stain on tumour tissue showing which repair proteins are present. Loss of MSH2 and MSH6 together points towards MSH2.
- Pathogenic variant
- A change known to break the gene. This is what people mean by an MSH2 fault or mutation.
- EPCAM
- A neighbouring gene. Some deletions in it switch MSH2 off without touching MSH2 itself.
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Side by side
How does MSH2 differ from the other Lynch genes?
MSH2
Most other Lynch genes
Among the higher-risk Lynch genes, with MLH1
MSH6 and PMS2 carry lower risks that start later
Urinary tract risk is clearly raised
Urinary tract risk is lower
Staining usually loses MSH2 and MSH6 together
MLH1 faults usually lose MLH1 and PMS2
Can be silenced by an EPCAM deletion
EPCAM affects MSH2 only
Being straight with you
What this page cannot tell you
It cannot tell you your own risk. Published risk figures for MSH2 vary between studies, and most were gathered outside India. Your counsellor will weigh your exact variant, your age and your family history before putting a figure on anything.
It cannot read your report
Two people with MSH2 on their report can be in very different positions. One may carry a clearly harmful change. Another may have a variant of uncertain significance, which should not change anything yet. What your specific variant means is a question for the counsellor who ordered the test.
Who this does not apply to
Most people with bowel or womb cancer do not have an MSH2 fault. A tumour that has lost MSH2 on staining is also not proof of an inherited fault, because both copies can be damaged inside the tumour alone. That question is settled by a blood test. Tumour-only testing to guide treatment is covered on our targeted therapy pages.
If you are unsure whether a report applies to you, call the helpline and someone will tell you honestly.Commonly believed
Four things families say about MSH2, and what is true
"An MSH2 fault means I will get bowel cancer."
It raises the risk. It does not settle it. Many carriers never develop bowel cancer, and regular colonoscopy removes most growths before they can become cancer.
"This is a women's gene, so the men can ignore it."
Men carry and pass on MSH2 just as women do. They also face the bowel and urinary tract risks themselves, and some studies suggest a raised prostate risk as well.
"My tumour lost MSH2, so I must have inherited it."
Not always. Both copies can be damaged inside the tumour during life, with nothing inherited at all. A blood test is what tells the two situations apart.
"One clear colonoscopy means I am safe for years."
Growths in Lynch syndrome can develop faster than usual. That is why checks are repeated far more often than for other people, even after a normal result.
Questions we are asked
Common questions about the MSH2 gene
Is MSH2 the same thing as Lynch syndrome?
Not quite. Lynch syndrome is the condition, and MSH2 is one of the genes that can cause it. Faults in MLH1, MSH6, PMS2 and EPCAM cause it too. The gene matters because each one carries a different pattern of risk and a slightly different plan of checks.
How is an MSH2 fault usually found?
Often it starts with a tumour. A bowel or womb cancer is stained, and the MSH2 and MSH6 proteins are missing. That prompts a blood test for an inherited fault. In other families it is found because a relative has already tested positive.
Can I pass an MSH2 fault to my children?
Each child of a carrier has a one in two chance of inheriting it, whether the child is a son or a daughter. A child who does not inherit the fault cannot pass it on. The chance is the same for every pregnancy, and it does not depend on earlier children.
Does MSH2 raise the risk of cancer in men?
Yes. Men who carry an MSH2 fault have a raised risk of bowel cancer and of urinary tract cancer. Some studies also point to a raised prostate risk. Men follow a surveillance plan just as women do, apart from the checks for the womb and ovary.
Why is my EPCAM result linked to MSH2?
EPCAM sits right beside MSH2 in your DNA. Certain deletions at the end of EPCAM spill over and switch MSH2 off in some tissues, mainly the bowel. The effect looks like an MSH2 fault on tumour staining, even though MSH2 itself is intact.
Does an MSH2 fault change how cancer is treated?
It can. Tumours with failed mismatch repair often respond well to immunotherapy, and the result may shape how much bowel is removed during surgery. Your oncologist will explain whether any of this applies to your cancer and its stage.
My report says MSH2 variant of uncertain significance.
The laboratory found a change and does not yet know whether it matters. It is not a positive result. Your checks should follow your family history, not the variant, and relatives should not be tested for it. Ask how you will hear if it is ever reclassified.
Where do I start after an MSH2 result?
Book a post-test session with a genetic counsellor, and take the full report, not a photograph of one page. Bring a list of relatives with any cancer and their ages. Call the CION helpline if you are unsure who to see first.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Sources
- MedlinePlus Genetics — MSH2 gene
- GeneReviews (NCBI) — Lynch Syndrome
- National Cancer Institute — Genetics of Colorectal Cancer (PDQ)
- MedlinePlus Genetics — Lynch syndrome
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
MSH2 mutation: which cancers and what riskThe organ-by-organ picture in more detailSurveillance for MSH2 carriersWhich checks you need and when they startEPCAM deletions that switch off MSH2If your report names EPCAM rather than MSH2Lynch syndrome: the complete pictureThe condition behind all five Lynch genes
Talk to us
Holding an MSH2 result and not sure what comes next?
Bring your report and a list of relatives with cancer, and we will help you understand the next steps with a genetic counsellor. One helpline serves every CION centre.