Medical Oncologist
CION Cancer Clinics
BAP1 family testing: who should be tested, and in what order | CION Cancer Clinics
Once one person is confirmed to carry an inherited BAP1 fault, their parents, brothers, sisters and children can each be tested for that exact fault. Each has a one in two chance of carrying it. This page explains who is usually offered a test, the order that makes sense, what each result means, and how to handle the family conversations that come with it. 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 BAP1 fault is found?
- Which relatives are usually offered a test?
- How does testing move through a family?
- What do the terms used in family testing mean?
- What does each result mean for that relative?
- What do families get wrong about BAP1 family testing?
- What can this page not tell you?
- Common questions about testing the family for BAP1
The short answer
Who in the family should be tested once a BAP1 fault is found?
Once one person is confirmed to carry an inherited BAP1 fault, their parents, brothers, sisters and children can each be offered a test for that exact fault. Each of them has a one in two chance of carrying it. The test either confirms they need regular checks or shows they can return to routine care.
Why relatives are worth testing
A BAP1 fault raises the risk of eye melanoma, mesothelioma, skin melanoma and kidney cancer. Carriers are offered eye, skin and kidney checks that can find these cancers small. Relatives who do not carry the fault can skip those checks, the travel and the worry. Either answer is useful.
Why the order matters
Testing works best when it starts from a confirmed result. Once the family's exact fault is known, every relative can be tested for that one change. This is quicker and cheaper than a broad gene panel, and the answer is much clearer. Testing a well relative without a known family fault often gives an answer nobody can act on.
Testing is always a choice. No relative has to be tested, and nobody should be tested without their own counselling first.Relative by relative
Which relatives are usually offered a test?
Testing moves outward from the person with the confirmed result, one branch of the family at a time.
Parents, brothers and sisters
Each has a one in two chance of carrying the fault. Testing the parents first often shows which side of the family it came from, and so which uncles, aunts and cousins to approach next.
Children
Each child of a carrier has a one in two chance. Because eye checks often start before adulthood in BAP1 families, testing in the teenage years is commonly discussed.
Your counsellor will weigh
- When eye checks would begin
- How ready the child is to understand
- What the child wants, where they are old enough
Aunts, uncles and cousins
Once the side of the family is known, relatives on that side can be offered testing in turn. Relatives on the other side usually need nothing further.
Relatives who have died
A stored tissue block from an old surgery or biopsy can sometimes be tested. This can settle which branch carried the fault when a key relative is no longer alive.
Not sure whether this applies to you?
Ask an oncologistStep by step
How does testing move through a family?
The first carrier gets a family letter
After the result session, the counsellor gives the carrier a letter naming the exact BAP1 change. Relatives take this letter to their own appointment.
Each relative has their own counselling
Before testing, the relative talks through what a positive or negative result would mean for them, for insurance and for their children. They can decide not to test.
A targeted test for the one known change
A blood or saliva sample is checked for that single change only. The laboratory knows exactly what to look for, which makes the answer clearer.
The result is given in person or by phone
A positive result leads to a surveillance plan. A negative result usually means routine care, and it also means that relative's children need no test.
Words you will hear
What do the terms used in family testing mean?
- Cascade testing
- Offering a test to relatives, step by step outward, once one person's fault is known.
- Predictive test
- A test in someone who is well, to see whether they carry the family's fault before any cancer appears.
- Familial variant
- The exact BAP1 change found in your family. Relatives are tested for this one change.
- First-degree relative
- A parent, brother, sister or child. Each shares half their genes with you.
- Obligate carrier
- Someone who must carry the fault because it passed through them, for example a parent between a carrier grandparent and a carrier child.
- Dominant inheritance
- One faulty copy is enough to raise risk, which is why each child of a carrier has a one in two chance.
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Side by side
What does each result mean for that relative?
Relative carries the family fault
Relative does not carry it
Eye, skin and kidney checks are usually advised
Routine care for age and background applies
Their children can be offered testing
Their children cannot inherit it from them
Avoiding asbestos and sunburn matters more
General health advice applies
New symptoms are looked into sooner
Symptoms are assessed in the usual way
Commonly believed
What do families get wrong about BAP1 family testing?
"Only the women in the family need testing."
BAP1 faults pass through men and women equally, and the cancers linked to BAP1 affect both. Brothers, sons and fathers need the same offer.
"If my brother tested negative, I must be negative too."
Each brother and sister has their own one in two chance. One sibling's result says nothing about another's. Each person needs their own test.
"I feel healthy, so the test is not for me."
Predictive testing is designed for people who feel well. Finding a carrier before any cancer appears is exactly when checks do the most good.
"We should test the youngest children straight away."
Timing is a decision for each family with their counsellor. Testing is usually linked to when the first check would begin, and older children are included in the decision.
Being straight with you
What can this page not tell you?
It cannot tell you which of your relatives carries the fault, or in what order your family should be tested. A genetic counsellor works that out from your family tree, the confirmed result and who is willing and able to be tested.
It cannot read your report
What your specific variant means is a question for the counsellor who ordered the test. Before relatives are tested, check that the family result came from blood or saliva. A BAP1 change found only in a tumour may not be inherited at all, and testing relatives for it would mislead them.
Who this does not apply to
If nobody in your family has a confirmed inherited BAP1 fault, family testing does not apply yet. The first step is assessing the relative who had cancer. Relatives who have already tested negative for the family's fault do not need testing again.
The family conversations
Telling relatives can be hard, especially where marriages are being arranged or families are not in touch. Your counsellor can help you plan what to say, and can write to relatives on your behalf.
Questions we are asked
Common questions about testing the family for BAP1
How do I tell my relatives about the result?
Share the family letter your counsellor gives you, which names the exact change. Many people start with parents and siblings, then let each of them pass it on. The counsellor can help you plan the words, or write to relatives directly.
Is testing a relative cheaper than the first test?
Usually, yes. The first test often looks across many genes. A relative is tested for one known change, which is simpler and quicker. Ask the laboratory for the price of a targeted family test before booking.
My relatives live in another state or abroad. Can they be tested?
Yes. They can take the family letter to a genetic service near them, or have counselling by video and send a saliva sample. The letter matters, because it tells their laboratory exactly which change to look for.
Will a positive result affect a marriage proposal?
It is a fair worry, and one families raise often. Who you tell, and when, is your own decision. Your counsellor can talk this through, including how the risk to future children would be explained.
Can a result affect insurance?
India has no dedicated law protecting people from genetic discrimination in insurance. Raise this with your counsellor before testing, not after. Some people choose to arrange cover first.
What if a relative refuses to be tested?
That is their right. Their children can still be tested directly if they wish. A relative who declines can still be offered the same checks as a carrier, based on the family history alone.
Can my parent's stored biopsy be tested after their death?
Sometimes. Hospitals keep tissue blocks from surgery and biopsies, and some can be tested for a known BAP1 change. Contact the hospital's pathology department early, as blocks are not kept forever.
Can counselling for my relatives be done in Telugu?
Yes. Counselling can be arranged in Telugu, and several relatives can come together if they prefer. Call the CION helpline, mention the BAP1 result and bring the family letter.
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 Bookshelf) — BAP1 Tumor Predisposition Syndrome
- MedlinePlus Genetics — BAP1 tumor predisposition syndrome
- NHS — Predictive genetic tests for cancer risk genes
- 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.
Keep reading
Related pages
BAP1 positive: what happens nextThe first steps for the person who tested positiveSurveillance for BAP1 carriersThe checks a relative who tests positive is offeredCascade testing: how a result moves through a familyThe general method, for any geneYour family letter and what to do with itHow to use the letter relatives will need
Talk to us
A BAP1 fault has been found in your family. Who should be tested next?
Bring the family letter and a list of relatives. A genetic counsellor can help you plan who to test and how to tell them. One helpline serves every CION centre.