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CION Cancer Clinics
Is my colon cancer hereditary? What it means for your family | CION Cancer Clinics
Most colon cancer is not inherited. It usually comes from gene changes that built up in the bowel lining over a lifetime, and it cannot be passed to your children. A small minority start with a fault present from birth, most often Lynch syndrome. This page explains the clues that point that way, the tumour test that usually asks the question first, and what a result means for your family. At CION Cancer Clinics in Hyderabad, our oncologists explain colon cancer in plain words and plan care around you and your family.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed October 2026, next review due October 2027
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On this page
- Was my colon cancer passed down to me?
- What makes doctors suspect an inherited colon cancer?
- How do doctors find out if my colon cancer is inherited?
- What do the words on a tumour or genetics report mean?
- What families often assume, and what is actually true
- What this page cannot tell you
- Common questions about inherited colon cancer
The short answer
Was my colon cancer passed down to me?
Probably not. Most colon cancer comes from changes that built up in the cells lining the bowel during your own life. Those changes sit only in the tumour. They were not inherited, and you cannot pass them on to your children.
A small minority of colon cancers begin differently. The person was born with a faulty gene in every cell of the body, inherited from a mother or a father. The American Cancer Society puts these inherited syndromes at roughly one in twenty colorectal cancers. Lynch syndrome is the most common of them.
Why the question matters after diagnosis
If your cancer is inherited, the answer reaches beyond you. Brothers, sisters and grown-up children may need colonoscopy earlier and more often. Women in a Lynch family may need checks for womb and ovarian cancer too. For you, the answer can shape treatment and how closely the rest of your bowel is watched afterwards.
You may already be partway to an answer
Most colon cancers are now tested for a feature called mismatch repair, or MMR. That tissue test is usually done on your biopsy or operation specimen to help plan treatment. It is also the first filter for Lynch syndrome. Ask your oncologist whether your report includes it.
Inherited does not mean anyone's fault. Nobody chooses the genes they are born with or the genes they pass on.Clues doctors look for
What makes doctors suspect an inherited colon cancer?
No single clue proves anything. Doctors weigh them together, and the more that apply, the stronger the case for a genetics referral.
Your age at diagnosis
Colon cancer before the age of fifty is a clue in its own right, because inherited faults tend to bring cancer on earlier. Most young patients still turn out to have no inherited syndrome, which is why the other clues matter too.
The pattern in your family
Two or more close relatives on one side with bowel cancer, or with the cancers that travel with it. In Lynch families those include womb, ovary, stomach, urinary tract and small bowel cancers.
Count everyone
- Parents, brothers, sisters and children first
- Then grandparents, uncles, aunts and cousins
- Men as well as women, on both sides
Many polyps
A large number of adenomas found over the years, or hundreds lining the bowel at once, points towards a polyposis syndrome. Familial adenomatous polyposis and MUTYH-associated polyposis are the two best known.
Your tumour test, or a second cancer
A tumour that is MMR-deficient, also called MSI-high, can be a sign of Lynch syndrome. So can a second separate cancer in you, such as a womb cancer years before the bowel cancer.
Most MMR-deficient tumours are not inherited. Further tissue tests come before any blood test.Not sure whether this applies to you?
Ask an oncologistFinding out
How do doctors find out if my colon cancer is inherited?
The tumour test
The laboratory checks your tumour tissue for the mismatch repair proteins, or for microsatellite instability. A normal result makes Lynch syndrome unlikely. It is often done already, and it helps plan your treatment as well.
Sorting out a deficient result
If a protein is missing, further tissue tests look for a BRAF change or for MLH1 methylation. Either one usually means the fault arose inside the tumour alone and was not inherited.
Genetic counselling and the family tree
A counsellor draws out your family, asks who had which cancer and at roughly what age, and explains what a test can and cannot tell you. You decide whether to go ahead.
The blood test
A blood or saliva sample goes to an accredited genetics laboratory, which looks for inherited faults in the genes linked to bowel cancer. The result can take several weeks.
Testing the family
If a fault is found, relatives can be tested for that exact fault. Those who do not carry it return to ordinary screening. Those who do start a closer watch, explained on screening for siblings and parents.
On your report
What do the words on a tumour or genetics report mean?
- MMR (mismatch repair)
- The cell's spell-checker for copied DNA. The tumour test looks for each of the proteins that do this job.
- MMR-deficient
- One or more of those proteins is missing from the tumour. It raises the question of Lynch syndrome but does not answer it.
- MSI-high
- Another way of showing the same spell-checker has failed, measured on the DNA rather than on the proteins.
- MLH1 methylation
- A chemical switch that silences one repair gene inside the tumour only. It points away from an inherited cause.
- Germline
- Present in every cell from birth, so it can pass to children. A somatic change is found in the tumour only.
- Variant of uncertain significance
- A gene change the laboratory cannot yet classify. It is not a positive result and should not change care on its own.
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Commonly believed
What families often assume, and what is actually true
"My father had colon cancer, so mine must be inherited."
Colon cancer is common, and families share kitchens, habits and age. One older relative with it is usually chance or shared risk rather than a single faulty gene. The pattern, the ages and your tumour test decide.
"If it is inherited, my children will definitely get cancer."
Each child of a parent with Lynch syndrome has an even chance of inheriting the fault. Those who inherit it carry a raised risk, not a certainty, and regular colonoscopy can find and remove polyps before they turn into cancer.
"A normal blood test means my family is safe."
It means no known inherited fault was found. Relatives may still need screening earlier than usual, based on the family history alone. Your counsellor will say what applies to each person.
"Someone in the family must be to blame."
Nobody chooses the genes they pass on, and a parent with an inherited fault may never have known. Finding it now is a chance to protect the next generation, not a judgement on the last one.
Being straight with you
What this page cannot tell you
It cannot tell you whether your own cancer is inherited. That needs your tumour report, your family history on both sides and, if those point that way, a genetic test arranged through your oncologist. A list of clues read online can make an ordinary family look alarming, or an unusual one look harmless.
It cannot read your report for you
Gene names, MMR results and variant classifications mean different things in different combinations. Bring the report to your appointment and ask what it means for you and for your family, in plain words.
Who this page is not for
If you do not have colon cancer yourself and are worried about a relative's diagnosis, start with family history of colon cancer instead. If your cancer is in the rectum, the genetic questions are the same, but treatment decisions sit with the rectal cancer pages.
At CION, your oncologist can review your tumour report, take your family history and arrange genetic counselling and testing through an accredited laboratory.Questions we are asked
Common questions about inherited colon cancer
Is colon cancer usually hereditary?
No. Most colon cancer is sporadic, meaning the gene changes built up in the bowel during life and are found only in the tumour. A small minority come from an inherited syndrome. Your age, your family pattern and your tumour test help your doctor judge whether yours might be one of them.
My tumour is MMR-deficient. Do I have Lynch syndrome?
Not necessarily. Most MMR-deficient colon cancers are caused by a change inside the tumour itself, often a silenced MLH1 gene. Extra tissue tests usually come first. If they do not explain the result, genetic counselling and a blood test are the next step.
Should I be tested if I was diagnosed young?
It is worth asking. Diagnosis before fifty is one of the clearest reasons to look for an inherited cause, even with no family history at all. Many young patients still test negative, but the answer matters for your brothers, sisters and children.
Who in my family needs to know?
If a fault is found, your parents, brothers, sisters and adult children come first, because each of them could carry it. Your counsellor can give you a family letter to share. Relatives then decide for themselves whether to be tested.
Will the result change my treatment?
Sometimes. An MMR-deficient tumour can change whether chemotherapy is advised after surgery in early stages, and it can open the door to immunotherapy in advanced disease. A confirmed syndrome may also change the operation discussed. The tumour board weighs all of this.
When should my children be tested?
For Lynch syndrome, testing usually waits until they are adults and can choose for themselves, because screening does not start in childhood. FAP is different. Polyps can begin in the teenage years, so testing is often offered earlier. Your counsellor will advise.
Can a relative who has died still be tested?
Sometimes. If their tumour was removed at surgery, a stored tissue block may still be tested for MMR. A blood test on a living relative is usually more useful. Ask the hospital that treated them whether the block has been kept.
Where do I start?
Ask your oncologist whether your tumour was tested for MMR or MSI, and what it showed. Write down who in your family had cancer, which kind and at roughly what age. Call the CION helpline if you want help arranging a genetics review.
Your Specialists
Meet CION's colon cancer specialists. Bring your colonoscopy, scan or biopsy report.
Our surgical and medical oncologists plan colon cancer care together: which operation, whether chemotherapy is needed, and the follow-up that comes after.
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
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
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Sources
- American Cancer Society — Colorectal Cancer Risk Factors
- NICE — Molecular testing strategies for Lynch syndrome in people with colorectal cancer
- National Cancer Institute — Genetic Testing Fact Sheet
- Cancer Research UK — Risks and causes of bowel cancer
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
Signs your colon cancer might be inheritedEach clue explained in more depthWhat an MMR-deficient result means for your familyIf your tumour report already says MMR-deficientGenetic testing after a colon cancer diagnosisThe next practical step once a test is suggestedTelling your family about inherited riskHow to start the conversation with relatives
Talk to us
Want your tumour report and family history looked at?
Bring your reports and a list of who in the family had cancer. A CION oncologist will tell you plainly whether a genetics referral makes sense, and arrange it if it does. One helpline serves every CION centre.