Medical Oncologist
CION Cancer Clinics
Testing the family for DICER1: who, when and in what order | CION Cancer Clinics
Once one person is found to carry a DICER1 fault, both parents are usually tested next, then brothers and sisters, then the children of anyone who carries it. Each relative is tested only for the exact fault already found. Unlike most adult cancer genes, young children are tested early, because checks in the first years of life genuinely help. This page explains who to test and why. 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 DICER1?
- What does testing mean for each person in the family?
- In what order does family testing usually happen?
- The words you will meet, in plain language
- What do the parents' results change?
- What families assume about DICER1 testing, and what is true
- What this page cannot tell you
- Common questions about testing the family for DICER1
The short answer
Who in the family should be tested for DICER1?
Once one person is found to carry a DICER1 fault, both parents are usually tested next, then brothers and sisters, then the children of anyone who carries it. Relatives are tested only for the exact fault already found in the family. That makes their test simpler, and the answer is usually clear.
Why children are tested early with DICER1
With many adult cancer genes, children are not tested until they can decide for themselves. DICER1 is different. The most serious tumour linked to it, a rare lung tumour, appears in babies and young children, and checks in those years genuinely help. So testing young brothers and sisters, and new babies in the family, is normally advised rather than delayed.
A tumour result is not the same as a family result
Sometimes DICER1 is first found in a test on a tumour. A change there may have happened only inside the tumour and may not be inherited at all. A blood or saliva test on the person answers that question. Only a fault found in blood or saliva is one that relatives can share. Tumour testing for treatment is a separate subject, covered under targeted therapy.
A relative who tests negative for the family's fault has the same risk as anyone else and does not need DICER1 checks.Relative by relative
What does testing mean for each person in the family?
DICER1 passes from parent to child. One faulty copy is enough, so it can come from the mother's side or the father's side.
Parents
Testing both parents shows which side the fault came from, or whether it arose new in the child. Many parents who carry it have never been ill, or had only a thyroid lump, and are surprised by the result.
Brothers and sisters
If a parent carries the fault, each brother or sister has a one in two chance of carrying it too. Young siblings matter most, because their risky years for the lung and kidney tumours may still be ahead of them.
Especially important for
- Babies and young children
- Any sibling with a cough, lump or cyst in the past
Children of a carrier
An adult carrier's own children each have a one in two chance of inheriting the fault. A baby born into the family can be tested soon after birth, so that checks can start on time if needed.
Wider family
Once you know which side it came from, aunts, uncles and cousins on that side can be offered testing. They may have young children of their own who would benefit from knowing.
Relatives on the other side of the family do not need testing for this fault.Not sure whether this applies to you?
Ask an oncologistIn practice
In what order does family testing usually happen?
Confirm the first result
The first person found, often a child who had a DICER1 tumour, has a blood or saliva test. This confirms the fault is inherited and gives its exact spelling for the rest of the family.
Test both parents
A counsellor explains what a positive result would mean before the sample is taken. If one parent carries the fault, the family knows which side to follow.
Test brothers and sisters
Young siblings are tested first. Those who carry the fault start checks suited to their age. Those who do not can stop worrying about DICER1.
Move outward along that side
The parent who carries the fault is usually the best person to tell their own brothers and sisters. A family letter from the counsellor can make this easier.
On the report
The words you will meet, in plain language
- Cascade testing
- Testing relatives one step at a time, outward from the first person found to carry the fault.
- Predictive test
- A test in someone who is well, looking only for the fault already known in the family.
- New fault
- A fault that arose for the first time in the child and was not inherited. Doctors may call this de novo.
- Mosaicism
- When a fault is present in only some of the body's cells. A parent can then test negative in blood yet still pass it on, which is uncommon.
- Carrier
- Someone who has the fault but no tumour. A carrier needs checks, not treatment.
- Variant of uncertain significance
- A spelling difference the laboratory cannot yet call harmful or harmless. It is not used to test relatives.
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Side by side
What do the parents' results change?
One parent carries the fault
Neither parent carries it
Each brother or sister has a one in two chance
Siblings' chance is low, but a counsellor may still suggest testing
That parent starts their own checks
Neither parent needs DICER1 checks
Relatives on that side can be offered testing
Wider relatives usually need no testing
The affected child's future children can inherit it
The affected child's future children can still inherit it
Commonly believed
What families assume about DICER1 testing, and what is true
"It came from the mother's side, because she had a thyroid problem."
Thyroid lumps are common in everyone. Only testing both parents shows where the fault came from. Guessing can send the wrong side of the family for checks and leave the right side unwarned.
"Our marriage was between cousins, so that caused it."
DICER1 needs only one faulty copy from one parent. A cousin marriage does not make it more likely. Blaming one side of the family helps nobody and can stop relatives from testing.
"Our other children look healthy, so they are fine."
Carriers usually look completely well. Lung cysts in a young child often cause no symptoms until they become a problem. Testing is the only way to know.
"If we test the children, no one will marry them."
A result is private medical information. What a family chooses to share, and when, is its own decision. A counsellor can help you think about marriage questions long before they arise.
Being straight with you
What this page cannot tell you
It cannot tell you which relatives in your family need testing first, or what a particular result means. That depends on your family tree, who has already been tested, and the exact variant found. What your specific variant means is a question for the counsellor who ordered the test.
It cannot settle questions of blame
Families sometimes argue about whose side a fault came from. No one chooses their genes, and a fault passed on unknowingly is nobody's fault. A counsellor can help explain this to elders who find it hard to accept.
Who this does not apply to
Most families with a thyroid lump or a kidney cyst in one person do not need DICER1 testing at all. This page is for families where the fault has already been found in blood or saliva, or where a doctor has suggested it.
India has no specific law protecting genetic results in insurance or employment, so it is worth discussing privacy before relatives are tested.Questions we are asked
Common questions about testing the family for DICER1
Is family testing a blood test?
Yes, a small blood sample is usual, and saliva is sometimes used instead. For babies, the sample is small. The laboratory looks only for the fault already known in your family, which keeps the result simple to read.
Is testing a relative cheaper than the first test?
Usually, yes, because the laboratory checks one known spot rather than reading the whole gene. Prices vary between laboratories. Ask for a written estimate before the sample is taken, and ask whether the laboratory that tested the first person can do it.
Can relatives in another town or abroad be tested?
Usually, yes. They can have the sample taken nearer home, as long as the laboratory has a copy of the first report showing the family's exact fault. Share that report with them so the right test is ordered.
Should a newborn in the family be tested?
If a parent carries the fault, testing a baby early is normally advised. The lung tumour linked to DICER1 is a risk in the first years of life, and checks work best when they start on time.
What if neither parent carries the fault?
Then the fault most likely arose for the first time in the child. Brothers and sisters then have a low chance of carrying it. Your counsellor may still suggest testing them, because a parent can rarely carry it in only some cells.
Can a relative refuse testing?
Yes. Adults decide for themselves, and that choice should be respected. If they decline, they can still be told the signs to watch for. For young children, parents decide, and a counsellor can help them weigh it.
Can we test before or during a pregnancy?
Options exist, and they are best discussed before a pregnancy begins. A counsellor can explain what is possible, what it involves and what it costs. Many families simply plan to test the baby soon after birth.
Who arranges family testing at CION?
A genetic counsellor plans who to test and in what order, and explains each result. Call the CION helpline with the first report to hand, and you will be booked for a family counselling session.
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
- GeneReviews (NCBI) — DICER1-Related Tumor Predisposition
- MedlinePlus Genetics — DICER1 syndrome
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
- MedlinePlus Genetics — What are the different ways a genetic condition can be inherited?
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
DICER1 positive: what happens nextThe first steps after a positive resultDICER1 syndrome in children: what to watch forWhat to watch for in a child who carries itSurveillance for DICER1 carriersThe checks a relative who tests positive will startThe DICER1 gene: what it doesHow the fault is passed down, in plain language
Talk to us
Not sure who in your family should be tested next?
Tell us who has already been tested and what the report found. We will help you reach a genetic counsellor who can plan testing for the rest of the family. One helpline serves every CION centre.