Medical Oncologist
CION Cancer Clinics
The MSH6 gene: what it does and why it matters | CION Cancer Clinics
MSH6 is one of the genes that proofread your DNA each time a cell divides. When one copy is faulty from birth, that proofreading can fail in a single cell later in life, and the person has Lynch syndrome. This page explains what the gene normally does, what goes wrong when it breaks, how it differs from the other Lynch genes, and why a fault raises risk rather than settling anything. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
NG
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
17+specialists on panel
15,000+patients treated
35+centres across Telangana & AP
4.8★ / 800+Google rating
On this page
- What does the MSH6 gene actually do?
- What a family should know about an MSH6 fault
- How does MSH6 fix a copying mistake?
- The words you will meet, in plain language
- How MSH6 differs from the other Lynch genes
- What this page cannot tell you
- Four things families say about MSH6, and what is true
- Common questions about the MSH6 gene
The short answer
What does the MSH6 gene actually do?
MSH6 is a proofreading gene. Every time a cell copies its DNA before dividing, small spelling mistakes creep in, and MSH6 helps spot them so they can be fixed. When MSH6 is faulty from birth, that proofreading can fail, and a person has a raised risk of certain cancers. This condition is called Lynch syndrome.
One of a team of four
MSH6 does not work alone. It belongs to a group of genes called the mismatch repair genes, along with MLH1, MSH2 and PMS2. A fault in any one of them causes Lynch syndrome. MSH6 works most closely with MSH2. The two proteins join as a pair, find the mistake and call in the rest of the repair team.
Why a faulty copy matters
You carry two copies of MSH6, one from each parent. If one copy is faulty, the other still does the job in almost every cell. Trouble starts only if the working copy is also damaged in one cell during life. That cell can then no longer correct its mistakes, and errors pile up until one of them switches on uncontrolled growth.
Carrying an MSH6 fault means a raised risk. It does not mean cancer is present or certain.Four facts to hold on to
What a family should know about an MSH6 fault
These four points explain most of what your counsellor will say about this gene.
It is a Lynch syndrome gene
A harmful MSH6 variant places a person in the Lynch syndrome group. The same care pathway applies, adjusted for the gene involved.
Cancers most linked to it
- Womb lining (endometrial) cancer
- Bowel cancer
- Less often, ovary, stomach and urinary tract
It is milder than MLH1 or MSH2
Across large studies, MSH6 carriers develop cancer less often and later in life than carriers of MLH1 or MSH2 faults. That is why their screening often starts a few years later.
The womb is the main concern for women
For women with an MSH6 fault, cancer of the womb lining is often a bigger risk than bowel cancer. It is frequently the first cancer to appear in the family.
It passes down either side
Each child of a carrier has a one in two chance of inheriting the fault. Men and women pass it on equally, and it can come from the father's side as easily as the mother's.
Not sure whether this applies to you?
Ask an oncologistInside the cell
How does MSH6 fix a copying mistake?
The cell copies its DNA
Before a cell divides, it copies billions of DNA letters. The copying machinery is very accurate, but now and then it puts the wrong letter in, or slips on a repeated stretch.
MSH6 and MSH2 find the mismatch
The MSH6 and MSH2 proteins travel along the new copy as a pair. They stop where a letter does not match its partner, or where a small loop of extra letters has formed.
The repair team arrives
Once the pair has found a mistake, MLH1 and PMS2 are called in. The faulty stretch is cut out and rewritten using the correct strand as a guide.
When the check fails
If both copies of MSH6 stop working in a cell, mistakes go unfixed. Short repeated stretches of DNA change length. Laboratories call this microsatellite instability, and it is a fingerprint of Lynch-type tumours.
On your report
The words you will meet, in plain language
- Mismatch repair (MMR)
- The cell's proofreading system for DNA copying mistakes. MSH6 is one of the four genes that run it.
- Lynch syndrome
- The inherited condition caused by a fault in any mismatch repair gene. It raises the risk of bowel, womb and several other cancers.
- Germline variant
- A change present from birth in every cell, and so able to pass to children. This is what an inherited test looks for.
- Pathogenic variant
- A change known to break the gene. Your report may also say likely pathogenic, which is treated the same way in practice.
- Microsatellite instability (MSI)
- A sign in tumour tissue that proofreading has failed. It is a test on the tumour, not on your blood.
- Immunohistochemistry (IHC)
- A stain on tumour tissue that shows which repair proteins are missing. Loss of MSH6 alone points towards this gene.
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
Side by side
How MSH6 differs from the other Lynch genes
MSH6
MLH1 and MSH2
Bowel cancer risk is raised, but lower
Bowel cancer risk is clearly higher
Cancers tend to appear later in life
Cancers more often appear young
Womb cancer is often the first sign
Bowel cancer is more often the first sign
Families often miss the classic criteria
Families more often show a clear pattern
Tumour MSI tests can look nearly normal
Tumour MSI tests are usually clearly abnormal
Being straight with you
What this page cannot tell you
It cannot tell you what your own result means. MSH6 variants range from clearly harmful to completely harmless, and many sit in between. What your specific variant means is a question for the counsellor who ordered the test.
It cannot give you a personal risk figure
Published risks for MSH6 come from families studied in Europe, North America and Australia. Studies from Indian families are small so far. Your own risk also depends on your age, sex, family history and whether you have already had cancer. A counsellor weighs all of that together.
Who this does not apply to
Most people do not need an MSH6 test. If your family has one older relative with bowel cancer and no womb cancer or young diagnoses, testing is unlikely to change anything. The test belongs with families who have a suggestive pattern, a relative whose tumour showed MSH6 loss, or a known fault already found in the family.
Tumour testing for treatment choices is a separate question, covered under targeted therapy.Commonly believed
Four things families say about MSH6, and what is true
"MSH6 is a bowel cancer gene, so the women in our family can relax."
For women, the womb lining is often the main risk. Womb cancer is frequently the first cancer diagnosed in an MSH6 family, and women carriers need their own plan.
"Nobody had cancer young, so it cannot be Lynch syndrome."
MSH6 cancers often appear later than with other Lynch genes. A family with diagnoses in their fifties and sixties can still carry an MSH6 fault, which is why these families are easily missed.
"The tumour test was normal, so there is no inherited fault."
MSH6 tumours sometimes show only weak instability on MSI testing. A stain that looks at the MSH6 protein directly is more reliable, and a blood test settles the question.
"Lower risk means we do not need screening."
Lower than MLH1 or MSH2 is still well above the general population. Screening simply starts a little later and is planned around the gene.
Questions we are asked
Common questions about the MSH6 gene
Is MSH6 the same as Lynch syndrome?
Not exactly. MSH6 is a gene, and Lynch syndrome is the condition caused by a harmful fault in it or in one of three other repair genes. Someone with an MSH6 fault has Lynch syndrome, with risks shaped by this particular gene.
Which cancers does an MSH6 fault raise the risk of?
Mainly cancer of the womb lining and the bowel. Ovarian, stomach, small bowel and urinary tract cancers are less common but still watched. The balance between them differs for men and women, which your counsellor will explain in detail.
Did I inherit it from my mother or my father?
It could be either. The family history often points to one side, and testing a parent, where possible, confirms it. Knowing which side matters because it tells you which aunts, uncles and cousins should also be offered a test.
Can an MSH6 fault be repaired or removed?
No. The fault is present in every cell from birth and cannot be corrected. What changes the outlook is regular screening, which finds problems early or before they become cancer, along with risk-reducing options discussed with your doctors.
Why did my tumour report mention MSH6 loss?
The lab stained the tumour and found the MSH6 protein missing. That can happen because of an inherited fault or because both copies were damaged inside the tumour only. A blood test is what tells the two apart, so ask for a genetics referral.
What if both parents carry an MSH6 fault?
This is rare, but more likely when parents are related by blood. A child who inherits two faulty copies can develop cancers in childhood. Couples in this position should see a genetic counsellor before or early in pregnancy to discuss their options.
Does MSH6 affect my cancer treatment?
It can. Tumours that have lost mismatch repair often respond well to immunotherapy, and surgeons may plan bowel surgery differently. Those decisions come from testing the tumour itself, which your oncologist arranges alongside the inherited result.
Where should I start if my relative tested positive?
Ask your relative for a copy of their report, because the exact variant name matters. Then book a genetic counselling appointment. You will usually be offered a simple test for that one variant, which is quicker and cheaper than a full panel.
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)
Medical Oncologist
Medical Oncologist
Want a specific doctor for your case? Mention them when booking.
Book Free ConsultationBook an appointment with our specialist
Share your name and number — we'll call you back within 30 minutes to schedule your consultation.
Sources
- MedlinePlus Genetics — MSH6 gene
- MedlinePlus Genetics — Lynch syndrome
- GeneReviews (NCBI) — Lynch Syndrome
- National Cancer Institute — Genetics of Colorectal Cancer (PDQ) – Health Professional Version
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
MSH6 mutation: which cancers and what riskThe organs involved, and how the risk comparesWhy MSH6 risks are lower and start laterThe biology behind the milder pictureSurveillance for MSH6 carriersWhich checks start when, organ by organLynch syndrome: the complete pictureThe condition this gene belongs to, across every organ
Talk to us
Has someone in your family been told they carry MSH6?
Bring the report and we will arrange genetic counselling to explain what it means for you and your relatives. We will also tell you honestly if testing is not needed. One helpline serves every CION centre.