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CION Cancer Clinics
CDKN2A in the family: who to test and in what order | CION Cancer Clinics
When one person carries a CDKN2A fault, each parent, brother, sister and adult child has a one in two chance of carrying it too. They are tested for that one known change, which is simpler and cheaper than the first test. This page explains who is offered testing first, how it is arranged, and why the answer decides who needs skin checks and pancreas scans. 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
- Who in the family should be tested for CDKN2A?
- Which relatives are offered testing, and when?
- How does family testing actually happen?
- What do the family-testing terms mean?
- What does a relative's result change?
- What this page cannot tell you
- What families say about testing relatives, and what is true
- Common questions about testing relatives for CDKN2A
The short answer
Who in the family should be tested for CDKN2A?
Start with the closest adult relatives of the person who carries the fault: parents, brothers, sisters and grown-up children. Each of them has a one in two chance of carrying the same change. Testing then moves outwards, one branch at a time, along the side of the family the fault came from.
Why a relative's test is simpler
The first test in a family searches CDKN2A and several related genes for any change. Once a fault has been found, relatives do not need that search again. The laboratory looks for the family's exact change and nothing else. The answer is usually a clear yes or no, and it costs far less than the first test.
Why the answer matters so much with this gene
A CDKN2A fault raises the risk of melanoma, a cancer of the skin's pigment cells, and of cancer of the pancreas. Carriers are offered regular skin checks and, from middle age, pancreas scans. A relative who tests negative does not need those pancreas scans. That one result can save years of travel, cost and worry.
A positive result in a relative is a statement about risk. It is not a diagnosis of cancer.In what order
Which relatives are offered testing, and when?
Families are tested in rings, starting closest to the carrier and moving outwards only where it helps.
Brothers and sisters
Each has a one in two chance of carrying the same change. Brothers matter as much as sisters. Melanoma and pancreatic cancer affect men and women alike, and a brother can pass the fault to his children.
Parents
Testing a living parent shows which side the fault came from. That tells you which aunts, uncles and cousins to approach, and spares the other side a test they do not need. If both parents have died, the family tree often points to the right side.
Adult children
Grown-up sons and daughters can be tested when they are ready. Sun protection and mole checks start well before any test, because they help every child in a melanoma-prone family whatever the gene result.
Usually waits
- Children who cannot yet decide for themselves
- Anyone not ready to hear the answer
Aunts, uncles and cousins
They come next, on the side the fault came from. Relatives in another district or state take the family letter with them, and the sample can often be collected close to their home.
Not sure whether this applies to you?
Ask an oncologistStep by step
How does family testing actually happen?
The carrier receives a family letter
After the result, the counsellor gives the carrier a letter naming the gene and the exact change. Any laboratory or doctor can use it, in Hyderabad or anywhere else.
The carrier tells relatives
CION does not contact relatives without permission. The carrier shares the news, often starting with brothers and sisters. The counsellor can help plan what to say, and in which language.
Each relative sees a counsellor first
A short conversation covers what each result would mean for that person. Insurance and marriage questions are raised before the sample is taken, not afterwards.
One sample, one change
Blood or saliva is tested for the family's exact CDKN2A change. The sample can often be collected in the relative's own district and sent on to the laboratory.
A results appointment, with a plan
The result is explained in Telugu, Hindi or English. A relative who carries the fault is given a skin and pancreas plan. One who does not is told whether any extra skin checks still make sense.
Words you will hear
What do the family-testing terms mean?
- Cascade testing
- Testing relatives one ring at a time, starting with the closest, once a fault has been found in the family.
- First-degree relative
- A parent, brother, sister or child. Each shares about half their genes with you.
- Known familial variant
- The exact CDKN2A change already found in your family. Relatives are tested for this change alone.
- Predictive test
- A test in someone who is well, to see whether they carry the family's fault before any cancer appears.
- Carrier
- Someone who has the fault but does not have cancer. A carrier needs a plan of checks, not treatment.
- Atypical moles
- Moles that are larger, irregular or unevenly coloured. They raise melanoma risk on their own, whatever the gene result.
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Side by side
What does a relative's result change?
The relative carries the fault
The relative does not carry it
Regular skin checks by a dermatologist
Ordinary skin care, plus checks if moles are unusual
Pancreas scans, usually from middle age
No pancreas scans needed for this reason
Stopping all tobacco becomes even more urgent
Stopping tobacco still helps, as it does for everyone
Their own children may be offered testing as adults
Their children cannot inherit this change from them
The family letter passes on to their branch
That branch of the family can stop here
Being straight with you
What this page cannot tell you
It cannot tell you which of your relatives carries the fault, or what a relative's own result means for them. What your specific variant means is a question for the counsellor who ordered the test.
It cannot give you Indian figures
Most of what is known about CDKN2A comes from families in Europe, Australia and North America, where melanoma is far more common. Melanoma is rarer in India, and studies in Indian families are very few. The way a fault behaves here may differ, and your counsellor will tell you what is current.
When the relative who had cancer has died
If the person with melanoma or pancreatic cancer was never tested, a stored tissue block from their surgery can sometimes be used. Otherwise the counsellor may suggest testing the closest living relative, knowing that a negative result is then harder to read.
Who this does not apply to
If no CDKN2A fault has been found in your family, this page is not your starting point. Most people with one relative who had melanoma or pancreatic cancer do not need a CDKN2A test at all. A change found only in a tumour report is covered on our targeted therapy pages.
Commonly believed
What families say about testing relatives, and what is true
"Melanoma is a white person's cancer, so this cannot matter to us."
Melanoma is less common in India, but it does occur, often on the soles, palms or under the nails. A family fault raises risk whatever your skin colour, and it raises pancreatic cancer risk too.
"Only the relatives with lots of moles need a test."
Some carriers have few moles, and many people with many moles carry no fault. The test answers the gene question. Moles are checked separately either way.
"We should test the children now, while we are at it."
Sun protection and watching moles help every child in the family, tested or not. Most counsellors suggest waiting until a child can choose for themselves.
"If I test negative, my children still need testing."
A child cannot inherit the family's change from a parent who does not carry it. Their risk from this fault is gone, though ordinary sun care still applies.
Questions we are asked
Common questions about testing relatives for CDKN2A
What are the chances my brother carries it too?
One in two. Each brother and sister of a carrier has an even chance of inheriting the change from the parent who carries it. Only a test for the family's exact change can say which way it went for each person.
Do my relatives need the full panel test I had?
Usually not. Once the family's CDKN2A change is known, relatives are tested for that change alone, which is simpler and cheaper. A relative who has had melanoma or pancreatic cancer may be offered a wider test, because another gene could also be involved.
Can relatives in another state or abroad be tested?
Yes. The family letter names the gene and the exact change, so any accredited laboratory can test for it. Relatives can take the letter to a genetics service near where they live, and counselling can often be done by video.
Should my teenage son or daughter be tested?
Most counsellors suggest waiting until they can decide for themselves. What matters in the teenage years is sun protection and regular skin checks, which are advised in carrier families whatever the gene result. Your counsellor can talk through your family's situation.
What if a relative does not want to know?
That is their right. Share the letter and let them decide in their own time. Suggest they still protect their skin and see a doctor about any changing mole. The letter stays valid, so the test can be done whenever they are ready.
If I test negative, can I skip all checks?
You do not need pancreas scans because of the family fault. Skin checks may still be advised if you have many unusual moles or a lot of sun damage. Your counsellor will say which ordinary checks apply to you.
Will testing affect insurance or marriage prospects?
India has no dedicated law on genetic discrimination. Both are fair questions to raise with a counsellor before testing, not afterwards. Some people arrange insurance cover first. The counsellor can also help you think about when and how to share a result.
Who arranges testing for my relatives?
Each relative arranges their own appointment, with the family letter in hand. If they live in Telangana, they can call the CION helpline and describe the letter. Someone will book the counselling and the test, and help plan skin and pancreas checks if needed.
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
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Sources
- MedlinePlus Genetics — CDKN2A gene
- National Cancer Institute — Genetics of Skin Cancer (PDQ) – Health Professional Version
- NHS — Predictive genetic tests for cancer risk genes
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
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
CDKN2A positive: what happens nextThe carrier's own next steps, before the family'sCDKN2A testing cost in HyderabadWhat a relative's test usually costsSurveillance for CDKN2A carriersThe skin and pancreas checks a carrying relative is offeredTesting children for inherited faultsWhy most gene tests wait until adulthood
Talk to us
Does a relative need testing for your family's CDKN2A change?
Bring the family letter and tell us who you would like tested. We can arrange counselling and the test, including for relatives who live in a district. One helpline serves every CION centre.