Medical Oncologist
CION Cancer Clinics
Signs your colon cancer might be inherited | CION Cancer Clinics
Colon cancer may be inherited when it appears at a young age, when several close relatives on one side have had bowel cancer, when one person has more than one linked cancer, or when a colonoscopy finds many polyps. Most colon cancer is not inherited. This page explains the signs doctors look for, what your tumour report may already show, and how to ask for genetic counselling. 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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The short answer
What are the signs that colon cancer runs in a family?
The clearest signs are colon cancer at a young age, several close relatives with bowel cancer on the same side of the family, one person with more than one linked cancer, and a colonoscopy that keeps finding many polyps. None of these proves an inherited cause. Each one is a good reason to ask for a genetic referral.
Most colon cancer is not inherited
Most colon cancers grow from faults that build up in the lining of the bowel over many years. Only a small share start with a fault that was present from birth and passed down a family. Shared food, shared habits, weight and simple age explain much of the clustering families notice. That is why doctors look for a pattern, not a single case.
The clue that may already be in your report
Your tumour is usually tested for mismatch repair, written as MMR, or microsatellite instability, written as MSI. These are the cell's spell-check system. A deficient MMR or MSI-high result can point to Lynch syndrome, the most common inherited cause. It can also be a change that happened only inside the tumour, which is common in older people. Read more on why every tumour gets this test.
A sign is a reason to ask. It is not a result.Patterns doctors look for
Which family patterns should make you ask about genes?
Doctors look at the whole family, on both the mother's and the father's side. These four patterns most often lead to a referral.
Diagnosed young
Colon or rectal cancer before fifty is the most common reason for a genetic referral. Inherited faults tend to bring cancer earlier than the faults that build up with age.
Most young patients still do not carry a fault. Age is a reason to check, not a verdict.Several relatives on one side
An inherited fault travels down one line of the family. Bowel cancer in close relatives on the same side, passing through more than one generation, is a pattern worth checking.
Often looks like
- A parent and a brother or sister affected
- Cancer in a grandparent, a parent and an uncle or aunt
- Relatives diagnosed younger than usual
Linked cancers
Lynch syndrome raises the risk of several cancers beyond the bowel. A family where bowel cancer sits beside these other cancers is a classic pattern.
- Womb (endometrial) or ovarian cancer
- Stomach or small bowel cancer
- Cancer of the tubes that drain the kidneys
- Two separate bowel cancers in one person
Many polyps
A polyp is a small growth on the bowel lining, and most are harmless. A colonoscopy that finds a large number of adenomas, the polyps that can turn into cancer, suggests a polyposis syndrome such as familial adenomatous polyposis or MUTYH-associated polyposis.
Not sure whether this applies to you?
Ask an oncologistIf a pattern fits
What should you do if one of these signs fits your family?
Draw the family tree
Write down every relative on both sides who had cancer, which organ, and roughly how old they were. Older relatives' illness was often called a stomach problem or a tumour, so ask aunts and uncles and look for old hospital papers.
Find your tumour test result
Ask your oncologist for the MMR or MSI result on your biopsy or operation report. If it shows a deficiency, ask whether the follow-up BRAF or MLH1 test was done to separate a tumour-only change from an inherited one.
Ask for genetic counselling
A genetic counsellor reads the tree and the report together and tells you honestly whether a test is worth doing. CION's oncologists can arrange this referral and the test through a partner laboratory.
Test the person with cancer first
A blood sample from the person who has the cancer is the most useful starting point. If a fault is found, healthy relatives can then be tested for that exact fault with a simple blood test.
Commonly believed
Four things families tell us, and what is actually true
"Only my father's side counts. That is our family."
A fault passes through the mother's side just as often. In many joint families the mother's relatives are less well known, and that is exactly where an inherited pattern gets missed.
"If it were inherited, my parents would have had it."
A parent can carry a fault and never develop cancer, or die of something else first. With MUTYH-associated polyposis, a child needs a faulty copy from each parent, so the parents are usually well and brothers and sisters are the ones affected. This is more likely when the parents are related by marriage.
"Young people get cancer from modern food now, so age means nothing."
Colon cancer in younger adults is rising, and most young cases are not inherited. A young diagnosis is still the strongest single reason to offer testing, because a fault is more likely to be found and the answer protects the family.
"If it runs in the family, my children will definitely get it."
Each child has a chance of not inheriting the fault at all. Those who do carry it face a raised risk, not a certainty, and earlier colonoscopy can find and remove polyps before they turn into cancer.
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Being straight with you
What this page cannot tell you
It cannot tell you whether your cancer is inherited. Only a genetic test can answer that, usually arranged after a counsellor has drawn your family tree and read your tumour report. The signs on this page make the question worth asking. They do not answer it. The Lynch syndrome page explains the most common inherited cause in more detail.
Who this does not apply to
If one relative was diagnosed at an older age, nobody was young, there are no linked cancers and your tumour MMR result is normal, an inherited cause is unlikely. Testing would rarely change your plan. Rectal cancer in a relative counts in the family tree in the same way as colon cancer. Anal cancer is a different disease with different causes, covered on the anal cancer pages.
It cannot read a genetic report
If you already hold a genetic report, the exact variant and how it is classified decide what it means. A variant of uncertain significance is not a positive result. Bring the report to a counsellor rather than searching the gene name online.
Not sure whether your family history counts? Call the helpline and describe it. Someone will tell you honestly whether a referral is worth making.Questions we are asked
Common questions about inherited colon cancer
My father had colon cancer in his seventies. Is mine inherited?
Probably not. One relative diagnosed at an older age is the usual pattern of colon cancer, not an inherited one. It does raise your own risk a little and may mean earlier screening for your family. A genetic referral usually needs more, such as a young diagnosis or a deficient tumour result.
Does it matter which side of the family the cancers are on?
Yes. An inherited fault travels down one line, so several relatives on the same side is more telling than the same number split across both sides. The fault can come from either parent, and the mother's side counts exactly as much as the father's.
What if I do not know what my relatives died of?
That is very common. Ask older relatives, and look for old discharge summaries or death certificates. Write down what you do know, even if it is only a stomach tumour in a grandfather. An incomplete tree is still useful, and your own tumour test can fill some of the gaps.
Can inherited colon cancer skip a generation?
The fault does not skip. What skips is the illness. A parent can carry the fault, stay well and pass it to a child who develops cancer. From the outside it looks as if a generation was missed, but the fault was there the whole time.
My tumour MMR test was normal. Can it still be inherited?
A normal MMR result makes Lynch syndrome much less likely. It does not rule out polyposis syndromes or rarer genes. If you were diagnosed young or the family pattern is strong, a counsellor may still suggest a blood test for a wider panel of genes.
Should my children be tested now?
Usually you are tested first. If a fault is found, adult children can be tested for that exact fault. For Lynch syndrome, testing normally waits until a child is an adult. Familial adenomatous polyposis is different, because checks start in the early teens, so testing is offered earlier.
Do the women in the family need anything different?
If Lynch syndrome is confirmed, women who carry the fault also have a raised risk of womb and ovarian cancer. A gynaecologist and a genetic counsellor plan how to watch for those. If no fault is found, their plan follows the family history alone.
Can CION help me find out whether my cancer is inherited?
Yes. CION's oncologists review your family tree and tumour reports, and can arrange genetic counselling and testing through a partner laboratory. Call the helpline with a list of who was diagnosed, with which cancer, and at roughly what age. One helpline serves every CION centre.
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
Is my colon cancer hereditary?The direct answer for someone who already has the diagnosisLynch syndrome and colon cancerThe most common inherited cause, explainedGenetic testing after a colon cancer diagnosisWhat the blood test involves and what it can changeGenetic counselling for colon cancer in HyderabadHow to get a referral and what happens at the appointment
Talk to us
Does your family history need a genetic referral?
Tell us who in your family was diagnosed, with which cancer and at what age, and send your tumour report if you have it. We will tell you honestly whether counselling and testing are worth arranging. One helpline serves every CION centre.