Medical Oncologist
CION Cancer Clinics
Genetic testing after a child's cancer diagnosis | CION Cancer Clinics
Some children with cancer are offered a genetic test for an inherited fault, alongside tests on the tumour itself. Most children tested will not carry one. When a fault is found, it can change some treatment choices, add checks for the future and tell the family whether brothers, sisters or parents need testing too. This page explains who is offered it, how it works and what it changes. 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
- Why would a child with cancer need a genetic test?
- Which children are offered genetic testing?
- What happens once testing is suggested?
- What do the words on your child's report mean?
- What does the result change for your child?
- What this page cannot tell you
- Four worries parents raise, and what is actually true
- Common questions about testing a child with cancer
The short answer
Why would a child with cancer need a genetic test?
To find out whether an inherited fault sits behind the cancer. Most childhood cancers are not inherited. A minority are, and in large studies that minority is somewhere below one child in ten. For certain cancer types, and for children with certain signs, the chance is much higher, which is why the question is asked.
Why it is asked now rather than later
The answer can change decisions during treatment. A few inherited faults make healthy cells more sensitive to radiation, so the team may prefer other options where they exist. The answer also shapes follow-up once treatment ends, and it tells the family whether brothers, sisters and parents need testing.
Two tests that are easily confused
A test on the tumour looks for changes inside the cancer to guide treatment. That is covered under tumour and targeted therapy testing. A germline test, the subject of this page, looks at the child's healthy cells for a fault present from birth.
A tumour result can hint at an inherited fault, but only a germline test can confirm one.Who is usually offered it
Which children are offered genetic testing?
The oncologist and counsellor look at four things. Any one of them can be enough to suggest a test.
The type of cancer
Some rare childhood cancers are so often linked to an inherited fault that testing is offered to nearly every child who has them.
Examples include
- Retinoblastoma, a cancer of the eye
- Cancer of the outer layer of the adrenal gland
- Choroid plexus carcinoma, a rare brain tumour
- Pleuropulmonary blastoma, a rare lung tumour
The family history
Other children or young adults in the family with cancer, several relatives on one side, or a known gene fault already found in a relative. Parents are asked about both sides.
Signs on the child's body
Some syndromes leave visible clues. Several pale brown patches on the skin, one side of the body growing larger than the other, or an unusually large head can all prompt a closer look.
More than one tumour
Cancer in both eyes, both kidneys, or two separate cancers in one child points strongly towards an inherited cause. So does a second cancer years after the first.
Not sure whether this applies to you?
Ask an oncologistStep by step
What happens once testing is suggested?
A conversation with the parents
A counsellor or the oncologist explains what the test looks for, what each result would mean and who else it might affect. Parents give consent, and an older child is asked for their agreement too.
The right sample
Usually a small blood sample. In leukaemia the blood carries cancer cells, so a small skin sample taken under a numbing injection is often used instead. After a bone marrow transplant, blood is not suitable either.
The laboratory analysis
Most children are tested on a panel, a set of genes known to be linked to childhood cancer. The laboratory reports any fault it finds and how confident it is about each one.
Results and a plan
Results are explained face to face or on a video call. If a fault is found, the plan covers treatment choices, follow-up checks and testing for the rest of the family.
On the report
What do the words on your child's report mean?
- Germline
- Present in every cell from birth, and so possibly inherited or passed on. This is what a predisposition test looks for.
- Somatic
- A change found only inside the tumour. It was not inherited and cannot be passed on to brothers, sisters or future children.
- Predisposition syndrome
- An inherited condition that raises the chance of certain cancers. It is a statement about risk, not a second diagnosis.
- Panel
- A test that reads a chosen group of genes at once, rather than one gene at a time.
- Pathogenic variant
- A change known to break the gene's instruction. This is what families mean when they say a gene fault was found.
- Variant of uncertain significance
- A change the laboratory cannot yet classify. It is not a positive result and should not change treatment on its own.
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Side by side
What does the result change for your child?
An inherited fault is found
No inherited fault is found
Some treatment choices may be adjusted to protect healthy cells
Treatment is planned on the cancer as usual
Regular checks continue after treatment ends
Routine follow-up after treatment applies
Both parents are offered testing for that exact fault
Parents usually need no genetic testing
Brothers and sisters may be tested if early checks help
The family history is still kept on record
Being straight with you
What this page cannot tell you
It cannot tell you whether your child should be tested. That depends on the exact cancer, what the doctors have seen during examination and what your family history shows. The oncologist treating your child and a genetic counsellor are the right people to decide that with you.
It cannot read your child's report
The same gene name can mean very different things depending on the exact variant and how the laboratory has classified it. What your specific variant means is a question for the counsellor who ordered the test, not for a search engine.
Who this does not apply to
Many children with common childhood cancers, no family history and no other signs are not offered germline testing, and that is a sound decision rather than an oversight. A negative result also does not rule out every possibility. It rules out the genes that were tested, which is why the family history still matters afterwards.
Commonly believed
Four worries parents raise, and what is actually true
"Testing will delay my child's treatment."
Treatment does not wait for the genetic result. The sample is taken alongside everything else, and the team starts the treatment the cancer needs. If the result arrives later and changes a choice, the plan is adjusted then.
"If my child has a gene fault, treatment will not work."
An inherited fault does not mean the cancer cannot be treated. In most cases it changes a few choices, such as limiting radiation or unnecessary scans, rather than the core of the plan.
"A negative result means the family is completely in the clear."
It is good news, but tests only read the genes they include, and science keeps finding new ones. If the family history is striking, the counsellor may suggest looking again in the future.
"We will have to pay to test the whole family straight away."
Nobody else is tested until the child's result is known. If a fault is found, relatives are tested only for that one fault, which is simpler and usually cheaper, and it happens one step at a time.
Questions we are asked
Common questions about testing a child with cancer
Does every child with cancer need genetic testing?
No. Most childhood cancers are not inherited, and testing is offered where the cancer type, the family history or signs on the child's body make an inherited cause more likely. Some centres abroad now test almost every child, but that approach is still being studied.
Can the test be done while my child is having chemotherapy?
Usually, yes. Chemotherapy does not change the genes your child was born with, so a blood sample during treatment gives a reliable result for most cancers. Leukaemia and bone marrow transplant are the exceptions, and the team will choose a different sample.
Why do they want a skin sample instead of blood?
In leukaemia, the blood carries cancer cells whose genes have changed. Testing it could mistake a change in the cancer for an inherited fault. A small skin sample gives the child's own healthy cells. It is taken with a numbing injection and heals with a tiny mark.
How long do results take?
A panel usually takes several weeks, and a skin sample takes longer because the cells must be grown in the laboratory first. If the result could change an urgent treatment decision, the team can ask for it to be prioritised. Ask for a likely date when the sample is sent.
Will a positive result change my child's treatment?
Sometimes, and usually in small ways. The team may avoid radiation where another option works as well, limit scans that use X-rays, or plan longer follow-up. For a few syndromes the result can open up a treatment option. Your child's oncologist will explain what applies.
Who pays for the test?
It depends on the laboratory and the scheme. Whether Aarogyasri or Ayushman Bharat covers germline testing for a child varies, so check with the scheme desk before assuming. Some laboratories and research programmes offer subsidised testing for children, and the counsellor can tell you what is available.
The report says variant of uncertain significance. What now?
It means the laboratory found a change and does not yet know whether it matters. It is not a positive result and should not change treatment or lead to testing relatives. Classifications are reviewed as evidence grows, so ask how you will be told if it changes.
Where do we start?
Ask your child's oncologist whether testing has been considered and why. Write down any cancers in the family on both sides, with rough ages. If you are unsure who to ask, 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
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Sources
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
- National Cancer Institute — Cancer in Children and Adolescents
- GeneReviews (NCBI) — Li-Fraumeni Syndrome
- GeneReviews (NCBI) — Retinoblastoma
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
When a childhood cancer suggests an inherited causeThe signs that make doctors ask the questionTesting the parents after a child tests positiveWhat happens next if a fault is foundSurveillance programmes for predisposed childrenThe checks that follow once treatment endsShould healthy siblings be tested?When brothers and sisters are offered a test
Talk to us
Wondering whether your child should be tested?
Tell us the diagnosis and anything you know about cancer in the family. We will help you raise the question with the right team and arrange counselling if testing makes sense. One helpline serves every CION centre.