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Testing the family after a PTEN fault is found | CION Cancer Clinics
Once one person carries a PTEN fault, parents, brothers, sisters and children are offered a test for that exact fault. Each child of a carrier has a one in two chance of inheriting it. This page explains who is tested and in what order, how the targeted test works, and what a positive or negative result means for each relative. 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 once a PTEN fault is found?
- Which relatives are offered a PTEN test, and why?
- How does family testing actually work?
- The family-testing words, in plain language
- What a relative's result changes for them
- What this page cannot tell you
- Four things families tell us, and what is actually true
- Common questions about testing the family for PTEN
The short answer
Who in the family should be tested once a PTEN fault is found?
Once one person is found to carry a PTEN fault, their parents, brothers, sisters and children are offered a test for that exact fault. Each child of a carrier has a one in two chance of inheriting it. The test is simple, cheaper than the first one, and gives a clear yes or no for that family's fault.
Why parents are often tested first
A PTEN fault is fairly often new in the person who has it, rather than inherited. Testing the parents shows which side it came from, or whether it came from neither. If neither parent carries it, the risk to brothers and sisters is low, and aunts, uncles and cousins usually need no test at all. That single step can save a large family a great deal of worry and money.
Why it is worth doing
A relative who carries the fault can start thyroid, skin and later breast, bowel and kidney checks at the right age. A relative who does not carry it can stop worrying and follow ordinary screening. Both answers are useful, and the second one is common.
Relatives are only tested for the fault already found. That is why the first report needs to be shared with them.Around the family tree
Which relatives are offered a PTEN test, and why?
Testing moves outwards from the person with the fault, one circle of relatives at a time.
Parents
Testing them shows where the fault came from. It tells the family which side of the tree, if any, needs testing next.
If a parent is positive
- That parent starts their own surveillance
- Their brothers and sisters are offered testing
Brothers and sisters
If a parent carries the fault, each sibling has a one in two chance of carrying it too. If neither parent carries it, their risk is low, though a counsellor may still offer a test.
Children
Each child of a carrier has a one in two chance of inheriting the fault. PTEN is one of the conditions where testing in childhood can be offered, because thyroid checks begin young.
The timing is discussed with the parents, never decided for them.The wider family
Aunts, uncles and cousins on the side the fault came from are offered testing next. In large Telangana families this can mean many people, so the counsellor helps you decide who to tell first.
Not sure whether this applies to you?
Ask an oncologistStep by step
How does family testing actually work?
The first report names the exact fault
The person tested first receives a report giving the precise PTEN change. Every later test in the family looks for that change only.
A family letter is written
The counsellor writes a letter you can share, explaining the fault in plain words. It helps relatives in other cities take it to their own doctor.
Each relative sees a counsellor
Before testing, each adult has their own conversation about what a result would mean. This can happen in Telugu, and often by video for relatives in the districts.
A blood or saliva sample is taken
The targeted test is quicker than the first one. The result comes back to the counsellor, who explains it to that relative alone.
The next circle is planned
A relative who tests positive becomes the starting point for their own children and siblings. A relative who tests negative closes that branch of the tree, and nobody below them needs testing.
Words you will hear
The family-testing words, in plain language
- Cascade testing
- Offering a test to relatives, one circle at a time, once a fault has been found in the family.
- First-degree relative
- A parent, brother, sister or child. They share about half their genes with you.
- Targeted test
- A test that looks only for the fault already found in the family. It is sometimes called a known-variant or site-specific test.
- De novo
- A fault that appeared for the first time in one person. Neither parent carries it, but that person's children can inherit it.
- Mosaicism
- When a fault is present in only some of a person's cells. A parent can occasionally carry it this way and test negative on blood.
- Predictive test
- A test in a well person, to find out whether they carry the family's fault before any illness appears.
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Side by side
What a relative's result changes for them
The relative carries the fault
The relative does not carry it
PTEN surveillance starts at the right age
Ordinary screening for age applies
Their own children are offered testing
Their children cannot inherit it from them
Symptoms are reported early and taken seriously
No extra checks are needed because of PTEN
Preventive options can be discussed later
No preventive surgery is needed for PTEN
Being straight with you
What this page cannot tell you
It cannot tell you exactly which relatives to approach, or in what order. That depends on who is alive, who is willing, which side the fault came from and whether anyone has already been tested. A counsellor draws out your family tree and plans it with you.
It cannot read anyone's result
What a specific variant means is a question for the counsellor who ordered the test. If a relative's report says something different from the family's first report, do not try to compare them yourself. Take both to the counsellor.
Who this does not apply to
Families where no PTEN fault was found are not offered targeted testing, because there is nothing specific to look for. That includes families with a clinical diagnosis of Cowden syndrome but a negative gene test. Relatives in those families are advised from the family history instead. Relatives on the side the fault did not come from also need no test.
Commonly believed
Four things families tell us, and what is actually true
"Only the women in the family need testing."
Men carry and pass on PTEN faults just as often. They also need thyroid, kidney, bowel and skin checks if they carry it.
"I feel perfectly well, so I cannot have it."
Many carriers feel entirely well for years. Some have only mild signs, such as a slightly large head or a few skin bumps, that nobody linked to a gene.
"If I test negative, my children still need testing."
If you do not carry the family's fault, you cannot pass it on. Your children do not need a PTEN test because of your side of the family.
"Telling relatives will only frighten them."
Most relatives would rather know. Half, on average, will learn they do not carry it, and those who do can start checks early.
Questions we are asked
Common questions about testing the family for PTEN
Do I have to tell my relatives?
It is your choice, and nobody will contact them without your agreement. Most families find a written family letter makes the conversation easier. Your counsellor can help you plan who to tell and how.
My parents both tested negative. How did I get it?
The fault most likely appeared for the first time in you. This is fairly common with PTEN. Your own children can still inherit it, so they are the ones to discuss testing for.
When should my child be tested?
PTEN is one of the conditions where childhood testing can help, because thyroid checks start young. The timing is discussed with you. Some parents test early, others wait for signs, and both are reasonable.
Does a cousin marriage change the risk?
It does not change the one in two chance for each child of a carrier. It can mean the same fault appears on more than one branch of a family tree, so tell the counsellor about any marriages between relatives.
Will a positive result affect a marriage proposal?
Families worry about this, and it is a fair worry. What to share, and when, is a personal decision. A counsellor can help you think it through and explain the condition clearly to a future spouse's family.
Can relatives abroad be tested?
Yes. Give them a copy of the family letter and the first report, and they can arrange a targeted test through a genetics service where they live. The fault is the same wherever the test is done.
Could a result affect insurance?
India has no dedicated law on genetic discrimination in insurance. Ask your counsellor about this before testing, not after, and read your existing policy's disclosure terms carefully.
How do we start testing the family?
Collect the first person's report and a list of close relatives on both sides. Book a counselling appointment, or call the CION helpline if you are not sure where to start, and someone will guide you.
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) — PTEN Hamartoma Tumor Syndrome
- MedlinePlus Genetics — PTEN gene
- MedlinePlus Genetics — What are the different ways a genetic condition can be inherited?
- 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.
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Related pages
Talk to us
Not sure who in the family to approach first?
Tell us who has been tested and who else is in the family. We will help you plan the next tests with a genetic counsellor, in Telugu if you prefer. One helpline serves every CION centre.