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CION Cancer Clinics
Testing the family after a SMARCB1 or SMARCA4 result | CION Cancer Clinics
After a child is found to carry a SMARCB1 or SMARCA4 fault, both parents are tested next, then any brothers and sisters. Many faults are new in the child, but siblings are still offered a test, because checks for a carrier start in early childhood. This page explains who is tested, in what order, what each result means, and what it cannot tell you. 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 SMARCB1 or SMARCA4?
- Which relatives are offered a test, and why?
- In what order does family testing usually happen?
- The words you will meet, in plain language
- What the parents' results mean for the other children
- What this page cannot tell you
- Four things families tell us, and what is actually true
- Common questions about testing the family
The short answer
Who in the family should be tested for SMARCB1 or SMARCA4?
Start with the child who had the rhabdoid tumour, then test both parents, then any brothers and sisters. The first test shows whether the fault is in the child's blood or only in the tumour. The parents' tests show whether the fault was inherited or appeared for the first time in that child.
Why this family test is different
With most cancer genes, testing is about adults and cancers that come later in life. Rhabdoid tumours mostly affect babies and very young children. So the most urgent question is usually about a younger brother or sister, or a baby not yet born. That is why these families are often tested quickly, and why children are included rather than asked to wait.
Many families face this after a loss
Some parents are asked about testing while their child is being treated. Others are asked after their child has died. Both are hard. A stored blood or tissue sample from the child can often still be used, so there is no need to decide in the first difficult weeks.
Testing the family is about protecting the children who are well. It is never about deciding who is to blame.Circle by circle
Which relatives are offered a test, and why?
Each person is tested for a different reason. The counsellor will explain which of these apply to your family.
The child with the tumour
A blood test shows whether the fault is present in every cell. If it is only in the tumour, the family risk is usually low. If it is in the blood, the rest of the family is offered testing for that exact change.
Both parents
Testing the mother and father shows whether one of them carries the fault. Many carrier parents are completely well. The result mainly matters for their other children and any future pregnancy.
Brothers and sisters
These are the relatives testing helps most. A child who carries the fault can start regular scans early, while a child who does not can skip them.
Offered even when
- Both parents test negative
- The brother or sister looks completely well
- The sibling was born after the diagnosis
The wider family
If a parent carries the fault, testing moves out to that parent's side: their brothers, sisters and their young children. With SMARCA4, adult women on that side may also want to discuss their own ovarian risk.
Not sure whether this applies to you?
Ask an oncologistIn practice
In what order does family testing usually happen?
Confirm the tumour type
The pathologist stains the tumour to see whether the SMARCB1 or SMARCA4 protein is missing. This tells the team which gene to look at in the blood.
Test the child's blood
A blood sample is checked for a fault in that gene, including missing pieces of the gene, which are common here. A stored sample can be used if the child has died.
Test both parents
Once the child's exact change is known, each parent is checked for that one change. This is a simpler and cheaper test than the first.
Test brothers and sisters
Siblings are tested for the same change, usually soon rather than later, because any checks that are needed start in early childhood.
Talk about future pregnancies
If the family plans another child, the counsellor explains the options before a pregnancy starts, so that nothing has to be decided in a rush.
On your report
The words you will meet, in plain language
- Germline
- Present in every cell from birth, so it can be passed on. A fault found only in the tumour is called somatic and is not passed on.
- De novo
- New in this child. Neither parent carries it in their blood. This is common with SMARCB1.
- Gonadal mosaicism
- The fault is present in some of a parent's egg or sperm cells but not in their blood. It is why siblings are still tested when both parents are negative.
- Carrier
- Someone who has the fault but has never had a tumour. Some carrier parents stay well for life.
- Penetrance
- How often the fault actually leads to a tumour. It is high for SMARCB1 and appears lower for SMARCA4.
- INI1 staining
- A laboratory stain on the tumour. When INI1 is missing, the SMARCB1 gene is not working in the tumour.
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Side by side
What the parents' results mean for the other children
A parent carries the fault
Neither parent carries it
Each brother or sister has a one in two chance of carrying it
The chance for siblings is low, but not zero
Siblings are tested, and so are that parent's relatives
Siblings are still offered a test
Each future pregnancy carries the same one in two chance
Future pregnancies carry a small chance
The parent's own health is discussed
The wider family usually needs no testing
Being straight with you
What this page cannot tell you
It cannot tell you what your child's result means. The exact change, the gene involved and the tumour type all shape the answer. What your specific variant means is a question for the counsellor who ordered the test, together with your child's oncologist.
It cannot set a scan plan for a sibling
Expert groups suggest regular brain and tummy scans for young children who carry a SMARCB1 fault. How often, and until what age, depends on the gene and the child. Studies so far are small, because these tumours are rare, so plans differ between centres.
Who this does not apply to
Most families where a tumour shows a missing SMARCB1 protein do not carry an inherited fault. Adults whose tumour report mentions SMARCB1 or SMARCA4, such as some sarcomas or lung cancers, usually have a change in the tumour only. That is tumour testing, which guides treatment and is explained on our targeted therapy pages. It does not mean the family needs testing.
Commonly believed
Four things families tell us, and what is actually true
"We are both negative, so our other children are safe."
The chance is much lower, but not zero. The fault can sit in a parent's egg or sperm cells without showing in their blood. That is why brothers and sisters are still offered a test.
"It came from the mother's side."
A fault can come from either parent, or from neither. In many families it is new in the child. Nobody caused it, and nothing in the pregnancy could have prevented it.
"Testing a baby is too early."
For most cancer genes, testing waits until adulthood. Rhabdoid tumours are different, because they appear in early childhood. Knowing early is what allows checks to start in time.
"A carrier parent will certainly get cancer."
Many carrier parents stay well. The risk is highest in the first years of life. An adult carrier's own risk is discussed individually, and for SMARCA4 that includes ovarian risk in women.
Questions we are asked
Common questions about testing the family
Can our child who died still be tested?
Often, yes. Hospitals keep tumour blocks, and sometimes a stored blood sample. Ask the hospital that treated your child whether tissue is available. Testing it can answer the family question, even though it cannot change what happened.
Should our newborn be tested?
If a brother or sister has a confirmed fault, testing a newborn is usually discussed early. A positive result means regular scans can start in infancy. A negative result spares the baby those scans. Your counsellor will guide the timing.
Can we have another baby without this worry?
When the family fault is known, testing during a future pregnancy, or of embryos during IVF, may be possible. These are personal choices, made within Indian law. Discuss them with a counsellor and a fetal medicine specialist before a pregnancy begins.
Does a parent who carries the fault need scans?
An adult carrier's own risk is usually lower than a young child's. For SMARCA4, women may be offered a discussion about the ovaries. For SMARCB1, the counsellor will explain what, if anything, applies to you.
Is this the same as schwannomatosis?
Different changes in SMARCB1 can cause schwannomatosis, a condition of benign nerve tumours in adults. It is not the same as rhabdoid tumour risk. The exact change on the report tells the counsellor which condition applies.
How long do family results take?
The first test on the child takes the longest. A parent or sibling tested for the known change usually gets a result sooner. If a pregnancy or a new baby is involved, tell the team so the testing can be prioritised.
Will relatives be told without our permission?
No. Your result is confidential. The counsellor can help you decide how to tell relatives and can give you a letter to share, but choosing who to tell remains with your family.
Where can we get this testing near Hyderabad?
Samples can be collected in Hyderabad and sent to an accredited laboratory, so you do not need to travel far. Call the CION helpline, and someone will point you to a genetic counsellor who sees families with rhabdoid tumours.
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)
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Sources
- GeneReviews (NCBI) — Rhabdoid Tumor Predisposition Syndrome
- MedlinePlus Genetics — SMARCB1 gene
- MedlinePlus Genetics — SMARCA4 gene
- National Cancer Institute — Childhood Central Nervous System Atypical Teratoid/Rhabdoid Tumor Treatment (PDQ) – Patient Version
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
SMARCB1 or SMARCA4 positive: what happens nextThe care plan for a child or parent who tests positiveRhabdoid tumour predisposition syndromeThe condition behind the result, explained in fullSMARCA4 and SMARCB1: which cancers and what riskWhich tumours are linked to each geneSMARCA4 and small cell carcinoma of the ovaryThe ovarian question for women on a carrier's side
Talk to us
Wondering whether your other children need a test?
Tell us what the report says and who is in the family. We will help you reach a genetic counsellor who sees families with rhabdoid tumours, at a pace that suits you. One helpline serves every CION centre.