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CION Cancer Clinics
Types of genetic test for cancer, compared | CION Cancer Clinics
Genetic tests for cancer either look at your blood for a fault you were born with, or at a tumour for faults the cancer picked up. Inherited tests then differ in how much they read, from one known spot to almost your whole genetic code. This page sets out each type, what it is for, and how a counsellor chooses the one that fits your family. At CION Cancer Clinics in Hyderabad, our oncologists review your family history with you and guide you to the right genetic counselling and testing.
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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 kinds of genetic test are used in cancer care?
- Which test reads how much?
- How does a counsellor decide which test to order?
- What do the testing words on a report mean?
- Which test fits which question?
- What this page cannot tell you
- Four things people believe about genetic tests
- Common questions about types of genetic test
The short answer
What kinds of genetic test are used in cancer care?
There are two broad kinds. One looks at your blood for a fault you were born with and could pass on. The other looks at the tumour for faults the cancer picked up on its own. Within inherited testing, the tests differ mainly in how much of your genetic code they read.
Inherited testing and tumour testing ask different questions
A blood test for an inherited fault asks whether your family carries a risk that relatives could share. A tumour test asks which faults are driving this particular cancer, usually to choose a treatment. The two can overlap, and a tumour result sometimes hints at an inherited fault, but one does not replace the other. This page covers inherited testing. Tumour testing is explained under targeted therapy.
Bigger is not the same as better
Inherited tests range from checking one known spot to reading almost all of your genetic code. A wider test finds more, but it also finds more changes nobody can yet explain. The right size is the one that matches your family's pattern, and a counsellor chooses it with you.
Most families who need testing are offered a panel of genes chosen for their pattern of cancers.From narrow to wide
Which test reads how much?
Think of your genetic code as a very large book. Each test reads a different amount of it.
A known family fault
Checks one exact spelling change already found in a relative. It is the simplest and usually the cheapest test, and it is what most relatives are offered.
Usually chosen when
- A relative's report already names the fault
- You want to know if you share it
A single gene
Reads one gene from end to end. It suits rare conditions with a very recognisable pattern, such as retinoblastoma in a child or a very large number of bowel polyps.
A multigene panel
Reads a chosen group of genes in one run. This is the usual test for someone with cancer whose age, cancer type or family history suggests an inherited cause.
Usually chosen when
- Several related cancers run in the family
- The pattern could fit more than one gene
The exome or the whole genome
Reads nearly every gene, or almost the entire code. These are mostly used in research or in unusual cases where a panel found nothing and the pattern is still striking.
Not sure whether this applies to you?
Ask an oncologistHow the choice is made
How does a counsellor decide which test to order?
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The family tree is drawn first
Who was diagnosed, with which cancer, and at roughly what age, on both sides of the family. The pattern points toward a group of genes before any test is chosen.
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The relative with cancer is tested first, where possible
Testing the person who has had cancer tells you whether there is a fault to look for at all. If they are negative, well relatives usually gain little from testing.
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The size of the test is matched to the pattern
A pattern that fits one condition gets a narrow test. A mixed pattern gets a wider panel. Very wide tests are kept for unusual situations.
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A check for missing sections is included
Some faults are whole sections of a gene that are missing or doubled. The counsellor makes sure the chosen test looks for these too.
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Relatives are offered the exact fault
Once a fault is found, brothers, sisters and children can be tested for that one change, which is simpler and quicker.
On your report
What do the testing words on a report mean?
- Germline
- Present in every cell from birth, so it can be passed on. Inherited testing looks for germline faults.
- Somatic
- Found only in the tumour, picked up during life. It cannot be passed to children.
- Diagnostic testing
- Testing someone who already has cancer, to find out whether an inherited fault explains it.
- Predictive testing
- Testing a well relative for a fault already known in the family, to see whether they share the risk.
- Deletion and duplication analysis
- A check for whole sections of a gene that are missing or doubled, which reading the letters alone can miss.
- Variant of uncertain significance
- A change the laboratory cannot yet call harmful or harmless. It should not change your care on its own.
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Side by side
Which test fits which question?
The test
What it is usually for
A known family fault
Relatives, once a fault is found in the family
A single gene
A rare pattern that clearly fits one gene
A multigene panel
Most people with a suspected inherited cancer
Exome or genome
Unusual cases where a panel found nothing
A home or online kit
Not a substitute for a clinical test
Being straight with you
What this page cannot tell you
It cannot tell you which test your family needs, or whether you need one at all. That depends on your family tree, and it needs a genetic counsellor or clinical geneticist who has drawn it out with you. A list of test types is a starting point for that conversation, not a replacement.
It cannot interpret a result
What your specific variant means is a question for the counsellor who ordered the test. Reports are written for trained readers, and the same gene name can mean very different things depending on the exact change. Please do not act on a result you have searched online.
Who this does not apply to
Most people do not need an inherited cancer test. One relative with a common cancer at an older age, with no young diagnoses and no rare cancers, is usually not a reason to test. A counsellor will tell you that as readily as they will recommend a test.
If you are unsure whether your family history counts, call the helpline and describe it. Someone will tell you honestly whether a referral is worth making.Commonly believed
Four things people believe about genetic tests
"The biggest test is always the safest choice."
A wider test finds more changes nobody can yet explain, and each one needs careful counselling. A test matched to your family's pattern usually gives a clearer answer.
"My tumour was already tested, so I know if it is inherited."
A tumour test looks for faults in the cancer. It may hint at an inherited fault, but it cannot confirm or rule one out. That needs a separate test on blood or saliva.
"A home kit from the internet tells me my cancer risk."
Many consumer kits check only a handful of known changes, not whole genes. A clear result from a kit does not mean you have no inherited fault, and a worrying one still needs a clinical test.
"A negative test means cancer cannot run in our family."
It means no fault was found in the genes that were read. Some families have more cancer than expected without any single gene to blame, and they are still watched closely from the family history.
Questions we are asked
Common questions about types of genetic test
Which genetic test do most families get?
A multigene panel, chosen for the pattern of cancers in the family. It reads a group of relevant genes in one run. Once a fault is found, relatives are then offered a simpler test for that exact change.
Is a blood test enough, or is tissue needed?
For inherited testing a blood sample is normally enough, and saliva is sometimes used. Tumour tissue answers a different question about the cancer itself. If the relative who had cancer has died, a stored tissue block from an old operation can sometimes still be tested.
Can a tumour test show an inherited fault?
Sometimes it raises the possibility. Some tumour reports flag a change that could have been present from birth. That finding then needs confirming with a blood test, and your oncologist or counsellor will tell you whether it is worth doing.
What is the difference between exome and genome testing?
The exome is the part of your code that holds the instructions for making proteins. The genome is almost all of it. Both read far more than a panel, and both return more uncertain findings, so they are used only in particular situations.
My result says variant of uncertain significance. What now?
It means the laboratory found a change and does not yet know whether it matters. It is not a positive result and should not lead to preventive surgery. Ask how you will be told if it is ever reclassified.
Are online genetic kits useful for cancer risk?
They are not a substitute for a clinical test. Many look at a few known changes rather than whole genes, and results are rarely explained by a counsellor. If a kit result worries you, bring it to a genetic clinic rather than acting on it.
Will a genetic test result affect my insurance?
India has no dedicated law on genetic discrimination in insurance, and the position has been argued in court rather than settled by statute. Raise it with your counsellor before testing, not afterwards. Some families choose to arrange cover first.
Where do I start if I think I need a test?
Write down who was diagnosed, with what, and at roughly what age, on both sides. Take that list to a genetic counsellor or your oncologist. Call the CION helpline if you are not sure who to approach, and ask whether counselling can be done in Telugu.
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
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
- MedlinePlus Genetics — What are the different types of genetic tests?
- Cancer Research UK — Inherited cancer genes and increased cancer risk
- NHS — Predictive genetic tests for cancer risk genes
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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Not sure which genetic test, if any, your family needs?
Tell us who in your family was diagnosed and at what age. We will tell you honestly whether a referral makes sense and arrange it if it does. One helpline serves every CION centre.