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BAP1 tumour predisposition syndrome, explained simply | CION Cancer Clinics
BAP1 tumour predisposition syndrome is a rare inherited condition caused by a fault in the BAP1 gene. It raises the risk of a small group of cancers, mainly eye melanoma, mesothelioma, kidney cancer and skin cancers, along with small skin bumps that are usually harmless. This page explains how it runs in families, how it is recognised and what a positive result 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
- What is BAP1 tumour predisposition syndrome?
- Which cancers and growths are linked to BAP1?
- How is BAP1 syndrome usually recognised in a family?
- What do the words around BAP1 mean in plain language?
- What does a positive result change, and what stays the same?
- What this page cannot tell you
- What do families get wrong about BAP1 syndrome?
- Common questions about BAP1 tumour predisposition syndrome
The short answer
What is BAP1 tumour predisposition syndrome?
It is a rare inherited condition caused by a faulty copy of the BAP1 gene, present from birth in every cell. People who carry it have a raised risk of a small, distinctive group of tumours: melanoma of the eye, mesothelioma, kidney cancer and some skin cancers. Many carriers stay well for years, and regular checks aim to find problems early.
What the BAP1 gene normally does
BAP1 is one of the body's tumour suppressor genes. It helps control which instructions a cell switches on and helps repair damaged DNA. When both copies stop working in a single cell, that cell loses a brake and can grow into a tumour. A carrier starts life with one copy already faulty, so only one more hit is needed.
How it runs in families
The fault is passed on in a dominant way. Each child of a carrier has a one in two chance of inheriting it, whether the child is a son or a daughter. It does not skip generations, though the cancers can. A parent may carry it, never become ill, and pass it on.
Carrying a BAP1 fault raises risk. It does not mean a cancer is certain.The tumour pattern
Which cancers and growths are linked to BAP1?
It is the combination that points to BAP1. One of these on its own is usually not inherited.
Melanoma of the eye
Also called uveal melanoma. It grows inside the eye, not on the skin, and is rare in the general population and rarer still in India. In a BAP1 family it is often the first clue. Regular eye checks can find it while it is small.
Mesothelioma
A cancer of the thin lining around the lungs or the abdomen. It is usually linked to asbestos. In BAP1 carriers it can appear with little or no known exposure, and asbestos raises the risk further.
No screening test for mesothelioma has been shown to help. Avoiding asbestos is the main protection.Kidney cancer
Usually the clear cell type, sometimes at a younger age than usual. Small kidney tumours cause no symptoms, which is why many plans include regular kidney scans.
Skin changes
Skin melanoma and basal cell cancer are more common in carriers. So are small, raised, skin-coloured or pinkish bumps called BAP1-inactivated melanocytic tumours. These bumps are usually harmless, but they are a valuable early clue.
Less certain links
- Meningioma, a tumour of the brain's lining
- Bile duct cancer
Not sure whether this applies to you?
Ask an oncologistHow it comes to light
How is BAP1 syndrome usually recognised in a family?
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A cancer raises the question
Often it is eye melanoma or mesothelioma, especially at a younger age, without asbestos exposure, or alongside another BAP1-type cancer in the family.
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The tumour may give a hint
A pathologist can stain tumour tissue to see whether the BAP1 protein is missing. Loss in the tumour is common and does not prove an inherited fault, but it prompts the question.
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A genetic counsellor draws the family tree
They ask about eye, lung lining, kidney and skin cancers on both sides, and at what ages. The pattern decides whether a blood test is worth doing.
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A blood test looks for the inherited fault
The test checks the BAP1 gene in ordinary blood cells. A fault found there is present from birth and can be inherited.
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Relatives are offered the same test
Once the exact fault is known, parents, brothers, sisters and adult children can be tested for that one change. A negative result in a relative usually ends the extra worry for them.
On your report
What do the words around BAP1 mean in plain language?
- BAP1
- The name of the gene. It is short for a longer protein name that you will rarely need.
- Germline
- Present in every cell from birth, and so able to be passed on. This is the kind of fault that makes the syndrome.
- Somatic
- Found only in the tumour, and not inherited. Many eye melanomas and mesotheliomas lose BAP1 this way in people with no syndrome.
- Uveal melanoma
- Melanoma that starts in the pigmented layer inside the eye, most often at the back of the eye.
- Mesothelioma
- Cancer of the mesothelium, the thin lining that covers the lungs, the abdomen and some other organs.
- BAP1-inactivated melanocytic tumour
- A small skin bump made of pigment cells that have lost BAP1. Usually harmless, sometimes removed to confirm what it is.
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Side by side
What does a positive result change, and what stays the same?
What changes
What stays the same
Regular eye checks by an eye specialist
You are not ill and need no treatment
Regular full-skin checks by a dermatologist
A cancer is not certain
Kidney scans on a set schedule
Daily life, work and food carry on as before
Avoiding asbestos becomes a priority
You can still marry and have children
Relatives can be tested for the same fault
Relatives who test negative need no extra checks
Being straight with you
What this page cannot tell you
It cannot tell you your own level of risk. BAP1 syndrome was described only recently, and the studies behind current advice are small. Most come from families in Europe, North America and Australia. How often each cancer appears in carriers, and at what age, is still being worked out, and Indian data are very limited.
It cannot interpret your result
A report may describe a BAP1 change as pathogenic, likely pathogenic or of uncertain significance, and each leads to a different plan. What your specific variant means is a question for the counsellor who ordered the test. Tumour testing to guide treatment is a separate question for your treating oncologist.
Who this does not apply to
Most people with eye melanoma, mesothelioma or kidney cancer do not have BAP1 syndrome. A single case in an older relative with clear asbestos exposure rarely points to it. Most people do not need this test, and a counsellor will say so honestly when that is the case.
If your family has two or more of these cancers, write down who had which and at what age. That list is the most useful thing to bring.Commonly believed
What do families get wrong about BAP1 syndrome?
"BAP1 only matters to people with eye cancer."
Eye melanoma is often the first clue, but the same fault raises the risk of mesothelioma, kidney cancer and skin cancers. Carriers need checks that cover all of these.
"We never worked with asbestos, so mesothelioma cannot happen."
In carriers it can appear with little or no known exposure. Hidden exposure from old roofing sheets or building work is also common. Avoiding asbestos still matters, because it adds to the risk.
"A BAP1 change in my tumour means my family is at risk."
Not necessarily. BAP1 is often lost only inside the tumour. Only a blood test for the inherited fault can tell whether relatives need testing.
"Those small skin bumps are just moles."
They may be. But several raised, skin-coloured bumps in someone from a BAP1 family deserve a dermatologist's look, because they can be an early sign of the syndrome.
Questions we are asked
Common questions about BAP1 tumour predisposition syndrome
How is BAP1 syndrome inherited?
Each child of a carrier has a one in two chance of inheriting the fault. Sons and daughters are equally likely to inherit it and to pass it on. A child who does not inherit it cannot pass it to their own children.
What checks does a carrier need?
Plans usually include regular eye examinations with the pupils widened, full-skin checks and kidney scans. There is no proven screening test for mesothelioma, so knowing its symptoms and avoiding asbestos matter more. Your team will set the start ages and timing for you.
Can the skin bumps be removed?
Yes. A dermatologist can remove a bump under local anaesthetic and send it for testing. This confirms what it is and can support the diagnosis in the family. Bumps that change, bleed or look different from the others should be seen promptly.
Should my children be tested?
Because regular eye checks may start in the teenage years, some families discuss testing then. Others wait until the child is an adult and can decide. The timing is a decision to make with your counsellor, weighing the benefit of early checks against the child's own choice.
Is BAP1 syndrome common in India?
It is rare everywhere, and very few Indian families have been described in published studies. That partly reflects how rarely testing has been done. Eye melanoma is also less common in people with darker skin, so a BAP1 family here may first come to light through another cancer.
How can a carrier avoid asbestos?
Do not cut, drill or break old cement roofing sheets and pipes, which often contain asbestos. Avoid jobs in demolition, brake repair and ship-breaking where exposure is likely. If your work involves old buildings, ask your employer about protection.
Does BAP1 change how a cancer is treated?
Treatment is still planned on the cancer itself. Some studies suggest mesothelioma in carriers may grow more slowly, but they are small. Tumour testing to guide treatment is handled separately by your oncologist and is a different test from the inherited one.
Where do I start if I think my family fits?
List who had eye melanoma, mesothelioma, kidney cancer or skin cancer, on both sides, and roughly at what age. Take that to a genetic counsellor or your oncologist. If you are not sure who to approach, 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)
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Sources
- GeneReviews (NCBI Bookshelf) — BAP1 Tumor Predisposition Syndrome
- MedlinePlus Genetics — BAP1 tumor predisposition syndrome
- MedlinePlus Genetics — BAP1 gene
- National Cancer Institute — Intraocular (Uveal) Melanoma 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.
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Tell us who in your family had eye, lung lining, kidney or skin cancer, and at what age. We will tell you honestly whether a genetic referral makes sense and help arrange it. One helpline serves every CION centre.