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Lynch-like syndrome: repair loss without an inherited fault | CION Cancer Clinics
Lynch-like syndrome means a tumour looks like a Lynch tumour on testing, but no inherited fault is found in the blood. It is an open question rather than a final answer. This page explains what can cause it, how doctors try to settle it, and what check-ups you and your close relatives may be advised to have in the meantime. At CION Cancer Clinics, our oncologists plan screening and care for families with an inherited cancer syndrome, explained in plain words.
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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 is Lynch-like syndrome?
- What can cause a Lynch-like result?
- How doctors try to settle the question
- The words you will meet, in plain language
- How Lynch-like syndrome compares with Lynch syndrome
- What this page cannot tell you
- Four things families tell us, and what is actually true
- Common questions about Lynch-like syndrome
The short answer
What is Lynch-like syndrome?
Lynch-like syndrome is the name for a tumour that looks like a Lynch tumour when the repair proteins are tested, but where no inherited fault is found in the blood. It is a label for an unanswered question rather than a diagnosis. Many people in this group turn out not to have an inherited condition at all.
Why the tumour and the blood disagree
Tests on the tumour showed that its DNA repair system had failed. In Lynch syndrome that happens because one faulty copy was inherited and the second was damaged later. In Lynch-like syndrome the blood test finds no inherited fault, and the usual acquired explanation has already been ruled out. Something else switched the repair genes off.
Why the family needs to know
Until the cause is clear, doctors cannot say for certain whether your brothers, sisters and children are at raised risk. They also cannot offer relatives a simple targeted test, because there is no family fault to test for. That uncertainty is the hardest part, and there are ways to narrow it.
Lynch-like syndrome is not the same as a negative result. It means the question is still open.Possible explanations
What can cause a Lynch-like result?
There are three main possibilities, and more than one team may need to work on it to tell them apart.
Two faults acquired in the tumour
Both copies of a repair gene were damaged inside the tumour during life. Nothing was inherited and nothing can be passed on. This is the most common explanation when it can be found. Proving it needs a deeper test on the tumour tissue itself.
If it is proven, relatives usually return to the screening advised by their family history alone.An inherited fault the test missed
Some inherited faults are hard to detect, especially large rearrangements or changes in PMS2, which has a look-alike gene nearby. A more detailed test sometimes finds one.
Worth asking about
- Which genes and methods were used
- Whether PMS2 was tested well
- Whether a newer test would add anything
A different gene
Faults in a few other genes can occasionally produce a similar tumour pattern. One of them, MUTYH, is inherited differently from Lynch and is usually tested alongside the repair genes. Your counsellor will decide whether any others need looking at.
Who this does not apply to
People whose tumour lost MLH1 because of a chemical switch called methylation, which is usually acquired with age. Also anyone with a confirmed inherited fault, who has Lynch syndrome itself.
Not sure whether this applies to you?
Ask an oncologistHow it is worked out
How doctors try to settle the question
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The tumour shows missing repair proteins
A routine stain on the tumour, or a test for genetic instability, shows the repair system has failed. This is often done for every bowel and womb cancer.
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The common acquired cause is ruled out
If MLH1 is the missing protein, the tumour is checked for methylation. If methylation is present, the cause is usually acquired and the family can usually relax.
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The blood is tested for an inherited fault
A blood test looks at the repair genes. If a fault is found, this is Lynch syndrome. If nothing is found, the label Lynch-like syndrome is used.
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The tumour is sequenced in more detail
Where tissue is available, a deeper tumour test can look for two acquired faults. Finding them usually means the cancer was not inherited.
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A family plan is agreed
If the cause is still unknown, the patient and close relatives are usually offered closer bowel checks, tailored to the family history.
On your report
The words you will meet, in plain language
- Mismatch repair deficient
- The tumour's DNA proofreading system has failed. Often shortened to dMMR on the report.
- MSI-high
- A sign of the same failure, measured by looking for small repeating stretches of DNA that have changed length.
- Immunohistochemistry
- A stain on the tumour tissue that shows which repair proteins are present and which are missing.
- Methylation
- A chemical switch that can turn MLH1 off inside a tumour. It is usually acquired, not inherited.
- Double somatic
- Two separate faults in the same repair gene, both acquired inside the tumour. It means the cancer was not inherited.
- Germline
- Present in every cell from birth, and so inheritable. Germline testing is done on blood or saliva.
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Side by side
How Lynch-like syndrome compares with Lynch syndrome
Lynch syndrome
Lynch-like syndrome
An inherited fault is found in the blood
No inherited fault is found
Relatives can have a targeted test
Relatives cannot be tested for a specific fault
Carriers follow a set Lynch programme
Checks are tailored to the family history
Relatives who test negative are released
Close relatives are usually watched as a precaution
Being straight with you
What this page cannot tell you
It cannot tell you which explanation applies to your family. That needs your tumour report, your blood report and often further tests, read together by a clinical geneticist. What your specific result means is a question for the counsellor who ordered the test.
What the evidence does not yet show
Studies suggest that relatives of people with Lynch-like syndrome sit somewhere between the general population and Lynch families in their bowel cancer risk. The studies are small and none come from India, so doctors tend to err on the side of caution. That means some relatives will have more colonoscopies than they turn out to need. Most families find that an acceptable trade while the answer is uncertain.
What this page does not cover
A tumour with a failed repair system can also change treatment, including whether immunotherapy may help. That is a question about the tumour, not about inheritance, and it is covered in our targeted therapy section. Your oncologist will discuss it with you separately.
If you have a tumour report mentioning MMR or MSI and are unsure what to do next, call the helpline. Someone will tell you honestly whether a genetics referral is worth making.Commonly believed
Four things families tell us, and what is actually true
"The blood test was negative, so the family is in the clear."
Not yet. In Lynch-like syndrome a negative blood test leaves the question open. Close relatives are usually advised to have bowel checks until the cause is clearer.
"Lynch-like means we definitely have Lynch syndrome."
It does not. Many people in this group have two faults acquired only in the tumour, which means nothing was inherited and nothing can be passed on.
"Once the label is given, nothing more can be done."
A deeper tumour test, a re-check of PMS2 or a newer blood test can sometimes settle it. Ask whether stored tissue from the surgery is still available.
"The tumour result tells us about our children's risk."
A tumour result only describes the tumour. Whether children are at risk depends on whether anything was inherited, which is a separate question with a separate test.
Questions we are asked
Common questions about Lynch-like syndrome
Is Lynch-like syndrome inherited?
Sometimes, but often not. In many people the cause turns out to be two faults acquired only in the tumour. In others, an inherited fault is later found. Until one of these is shown, doctors treat the family with some caution.
What check-ups do I need myself?
People who have had a Lynch-like cancer are usually offered regular colonoscopy, often more often than the general population. Women may also be advised about womb checks. Your doctor will set a plan based on your history.
Should my brothers, sisters and children have colonoscopy?
Close adult relatives are often advised to start bowel checks earlier and repeat them more often than usual. The exact plan depends on who else in the family has had cancer.
Can my old surgery tissue still be tested?
Often, yes. Hospitals store tissue blocks from surgery, and these can sometimes be used for deeper tumour testing years later. Ask the hospital where your surgery was done whether the block is still available.
Can the answer change over time?
Yes. Testing methods improve, and a fault missed earlier can sometimes be found later. It is reasonable to ask your counsellor every few years whether a newer test would add anything.
Does this change my cancer treatment?
The tumour's repair status can matter for treatment, whatever the inherited result. That part is decided by your oncologist based on the tumour. The inherited question mainly affects your future checks and your family.
Is Lynch-like syndrome common in India?
We do not have good Indian figures. Tumour testing for repair proteins is becoming more routine here, so more families are meeting this label. Most of what is known comes from studies abroad.
Who should I see about this?
A genetic counsellor or clinical geneticist, ideally with both your tumour and blood reports in hand. If you are not sure who to approach, call the CION helpline and someone will point you to the right clinic.
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
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Sources
- National Cancer Institute — Genetics of Colorectal Cancer (PDQ) - Health Professional Version
- GeneReviews (NCBI) — Lynch Syndrome
- 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
MMR IHC on the tumour as a route into Lynch testingHow the tumour stain that starts all this worksMLH1 promoter methylationThe common acquired cause that has to be ruled out firstAmsterdam and Bethesda criteria explainedHow family history is used when the tests cannot settle itLynch syndrome: the complete pictureWhat a confirmed Lynch diagnosis would mean instead
Talk to us
Holding a tumour report that mentions MMR or MSI?
Bring your tumour report and any blood test results. A genetics specialist will explain what has been ruled out, what could still be checked and what your family should do meanwhile. One helpline serves every CION centre.