Medical Oncologist
CION Cancer Clinics
The PTEN gene: what it does and why it matters | CION Cancer Clinics
PTEN is a gene that acts as a brake on cell growth. When one copy is faulty from birth, that brake is weaker in every cell. The result is harmless overgrowths in the skin, thyroid and bowel, and a raised risk of breast, thyroid, womb and a few other cancers. This page explains what the gene does, where a fault shows up and what it does not mean. 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
- What does the PTEN gene actually do?
- Which parts of the body does a PTEN fault affect?
- How does a faulty PTEN brake lead to overgrowth?
- The words you will meet, in plain language
- Is a PTEN change in a tumour the same as an inherited one?
- What this page cannot tell you
- Four things families tell us about PTEN, and what is true
- Common questions about the PTEN gene
The short answer
What does the PTEN gene actually do?
PTEN is a brake on cell growth. It makes a protein that switches off a signal telling cells to grow, divide and survive. When the brake works, cells grow only when the body needs them. When it is faulty, that growth signal stays on for longer than it should.
What changes when one copy is faulty from birth
Everyone has two copies of PTEN, one from each parent. A person born with one faulty copy still has one working brake in every cell, so most cells behave normally. The trouble is that the remaining copy can be lost in a single cell during life. That cell then has no brake at all, and it can start to overgrow.
Why it causes harmless growths as well as cancers
Most of what a PTEN fault produces is not cancer. It is small, harmless overgrowth of normal tissue: bumps on the skin, polyps in the bowel, lumps in the thyroid or breast. Doctors call these hamartomas. Alongside them comes a raised risk of a few specific cancers, which is why carriers are offered regular checks.
A PTEN fault is uncommon. Most people with a thyroid lump or a few skin bumps do not carry one.Where it shows up
Which parts of the body does a PTEN fault affect?
The raised cancer risk is concentrated in a handful of organs. The harmless growths can appear almost anywhere.
Breast
Breast cancer is the main cancer risk for women with a PTEN fault, and the risk is substantially higher than in the general population. Harmless breast lumps and cysts are also common, which can make checks harder to read.
Thyroid
Thyroid nodules and an enlarged thyroid are very common. There is also a raised risk of thyroid cancer, including a type called follicular cancer that is rarer in the general population.
Thyroid checks may start in childhood.Womb
Women with a PTEN fault have a raised risk of cancer of the womb lining. Unusual or heavy bleeding, or any bleeding after the menopause, should be reported rather than put down to fibroids or age.
Kidney, bowel and skin
Risk is also raised, to a smaller degree, in these organs.
What doctors look out for
- Kidney cancer, watched with scans in adult life
- Many polyps in the bowel, found at colonoscopy
- Melanoma, a skin cancer, alongside harmless skin bumps
Not sure whether this applies to you?
Ask an oncologistInside the cell
How does a faulty PTEN brake lead to overgrowth?
A growth signal arrives
Hormones and growth factors in the blood tell a cell to grow. Inside the cell, this sets off a chain of messages often called the PI3K pathway, which pushes the cell to divide and to survive.
PTEN switches the signal off
In a healthy cell, the PTEN protein removes one of the key messages in that chain. The signal fades, and the cell stops growing once the job is done.
A fault leaves one working copy
Someone born with a PTEN fault has half the usual supply of the brake in every cell. Most cells cope, which is why many carriers feel entirely well for years.
The second copy is lost in one cell
Ordinary copying errors can knock out the working copy in a single cell. With no brake left, the growth signal stays on, and that cell and its descendants can overgrow into a hamartoma or, less often, a cancer.
On your report
The words you will meet, in plain language
- Tumour suppressor gene
- A gene whose job is to hold cell growth back. PTEN is one. Cancer risk rises when both copies stop working in the same cell.
- Hamartoma
- A harmless overgrowth of the normal tissue in that part of the body. It is not cancer and does not spread.
- PTEN hamartoma tumour syndrome
- The umbrella name for every condition caused by an inherited PTEN fault. You may see it shortened to PHTS.
- Cowden syndrome
- The best-known condition under that umbrella, usually recognised in adults from skin signs, thyroid disease and breast or womb problems.
- Macrocephaly
- A head size larger than usual for age and height. It is one of the most consistent signs of a PTEN fault in both children and adults.
- Germline
- Present in every cell from birth, and therefore inheritable. A PTEN change found only in a tumour is called somatic and is not passed on.
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Two different results
Is a PTEN change in a tumour the same as an inherited one?
Inherited PTEN fault
PTEN change found only in a tumour
Present in every cell from birth
Present only in the cancer cells
Found on a blood or saliva test
Found on a test of the tumour tissue
Can be passed to children
Cannot be passed on
Leads to lifelong checks and family testing
May help choose treatment for that cancer
Being straight with you
What this page cannot tell you
It cannot tell you whether you or your child carries a PTEN fault. That is answered by a genetic counsellor or clinical geneticist who examines the signs, draws out the family tree and arranges a blood test if it is warranted. What your specific variant means is a question for the counsellor who ordered the test.
It cannot read a tumour report for you
PTEN changes are often found inside tumours of the womb, prostate, brain and breast. Those changes usually arose in the tumour alone. They are part of targeted therapy planning, not proof of an inherited fault. Your oncologist will say whether a blood test is also worth doing.
Who this does not apply to
Most people do not need a PTEN test. A single thyroid nodule, a few skin tags, or a large head that runs in the family are all common, and on their own they do not point to PTEN. Testing is considered when several of these signs cluster in one person or one family.
Commonly believed
Four things families tell us about PTEN, and what is true
"PTEN is just another breast cancer gene."
Breast risk matters, but a PTEN fault affects the thyroid, womb, kidney, bowel and skin too. A plan that only watches the breasts misses most of what the gene does.
"The skin bumps mean the cancer has started."
The skin signs are harmless overgrowths. They are often the clue that leads to diagnosis, but they are not cancer and do not turn into cancer.
"A PTEN change in my tumour means my children are at risk."
Usually not. PTEN changes are common inside tumours and most arose there alone. Only a blood test shows whether a fault was inherited and could be passed on.
"If it is in the genes, there is nothing to be done."
The fault itself cannot be corrected or reversed. What can change is timing. Regular checks aim to find a cancer small and early, when treatment is simpler.
Questions we are asked
Common questions about the PTEN gene
Is a PTEN fault the same as Cowden syndrome?
Nearly. Cowden syndrome is the best-known condition caused by an inherited PTEN fault, but not the only one. The umbrella term PTEN hamartoma tumour syndrome covers all of them, including conditions first recognised in children. What matters for your care is the fault, not which label was written down first.
How is a PTEN fault usually discovered?
Often through a combination of signs rather than a cancer. A large head size, particular skin bumps, thyroid disease, many bowel polyps or a child with developmental delay can all lead a doctor to suspect it. A blood test then confirms or rules it out.
Can men carry a PTEN fault?
Yes. Men and women are equally likely to inherit it and to pass it on. Men share the thyroid, kidney, bowel and skin risks, and some men with a PTEN fault do develop breast cancer. A man should never be left out of the family tree.
What are the chances of passing it to a child?
Each child of a carrier has a one in two chance of inheriting the fault, whether the carrier is the mother or the father. Some people have a new fault that neither parent carried. A counsellor can explain what that means for brothers, sisters and children.
Does a PTEN fault affect learning or behaviour?
In some children, yes. A PTEN fault is one known cause of developmental delay and of autism with a large head size. Many carriers have no learning difficulty at all. Children found to carry a fault are usually offered a developmental assessment.
Can PTEN be tested on a standard breast cancer panel?
Most hereditary breast cancer panels include PTEN. A panel ordered for a different reason may not. If a doctor suspects PTEN from the physical signs, they will make sure the test chosen covers the whole gene.
Are there medicines that correct a PTEN fault?
Not yet. Drugs that act on the growth signal PTEN normally controls are being studied, but the studies so far are small and none is a routine treatment for carriers. Care today rests on regular checks and early treatment of anything found.
Who should I see if I think my family has PTEN signs?
Start with a genetic counsellor or clinical geneticist. Make a list of who has had thyroid disease, breast or womb cancer, bowel polyps or a large head, and at what age. Call the CION helpline if you are unsure where to begin.
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
- MedlinePlus Genetics — PTEN gene
- GeneReviews (NCBI) — PTEN Hamartoma Tumor Syndrome
- MedlinePlus Genetics — Cowden syndrome
- NCCN — Genetic/Familial High-Risk Assessment: Breast, Ovarian, Pancreatic, and Prostate
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
PTEN mutation: which cancers and what riskThe size of the risk, organ by organPTEN hamartoma tumour syndrome: the umbrella termHow Cowden syndrome and the childhood conditions fit togetherHead circumference, skin findings and PTENThe physical signs that lead doctors to testSurveillance for PTEN carriersWhich checks a carrier needs, and when
Talk to us
Has a doctor mentioned PTEN or Cowden syndrome?
Bring the report, or a list of the signs in your family, to a genetic counsellor who can explain what it means. We can arrange that appointment and help you work out who else should be checked. One helpline serves every CION centre.