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Tumour testing and germline testing: how the two fit together | CION Cancer Clinics
A tumour test reads the cancer to help choose a medicine. A germline test reads your blood to find a fault you were born with and could share with relatives. They answer different questions, but a small group of genes matters to both. This page explains what each test looks at, how a tumour result can lead to a family test, and who explains each report. 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
- How are tumour testing and germline testing different?
- What does each test actually look at?
- How does a tumour result lead to a family test?
- The words you will meet on both reports
- Tumour test or germline test: what does each change?
- Four mix-ups families make between the two tests
- What this page cannot tell you
- Common questions about tumour and germline testing
The short answer
How are tumour testing and germline testing different?
A tumour test reads the cancer to help choose a medicine. A germline test reads your blood to find a fault you were born with, one your relatives might share. They answer different questions, and one rarely stands in for the other.
Where the two tests meet
The overlap is a small group of genes that matter for both treatment and family, such as BRCA1, BRCA2 and the genes behind Lynch syndrome. A change in one of these genes found in the tumour can hint that it was inherited. An inherited fault found in blood can open a treatment option for the person who has cancer. That is why the two results are best read together.
Who owns which question
Your oncologist orders tumour testing and uses it to plan treatment. That side is explained on our targeted therapy pages. A genetic counsellor or clinical geneticist handles the germline question: what it means for you, your brothers and sisters, and your children. This page is about how the two hand over to each other.
A tumour result describes the cancer. A germline result describes the person and the family.Two tests, two questions
What does each test actually look at?
The names on the request forms sound alike. The sample, the question and the people it affects are all different.
Tumour testing
Reads changes inside the cancer cells. Most of these arose during life, in that organ only, and cannot be passed to a child.
Usually needs
- Tissue from a biopsy or surgery
- Sometimes blood carrying tumour DNA
- An oncologist's request
Germline testing
Reads the DNA in ordinary cells, which is the same in every cell since birth. A fault found here can be passed on, and relatives can be tested for it.
Usually needs
- A blood or saliva sample
- Counselling before and after
- Consent that covers the family
Where they overlap
Some genes matter to both. A BRCA fault can guide treatment and also tell sisters and daughters about their own risk. The same gene can appear on both reports, meaning quite different things.
What a tumour test cannot settle
A tumour-only report cannot always say whether a change was inherited. Only a comparison with normal DNA, usually from blood, can answer that.
Not sure whether this applies to you?
Ask an oncologistHow the results travel
How does a tumour result lead to a family test?
-
The tumour is tested to plan treatment
Your oncologist sends tissue to look for changes a medicine can target. The report lists what was found in the cancer.
-
A change could have been inherited
Some changes, in some genes, are often present from birth. The report or your oncologist flags these as needing a germline check.
-
You are referred for counselling
A counsellor explains what a blood test could show and what it would mean for relatives. You decide whether to go ahead.
-
A blood test gives the answer
If the same fault is in your blood, it was inherited. If it is not, it arose in the tumour alone and relatives are not affected by it.
-
Both plans are updated
Treatment may change for you. Relatives may be offered a simple test for that exact fault, and screening plans follow from their results.
On your reports
The words you will meet on both reports
- Somatic
- A change found only in the cancer cells. It arose during life and is not passed to children.
- Germline
- A change present from birth in every cell, including egg and sperm cells. It can be passed on.
- Tumour-normal testing
- Testing the tumour and a blood sample side by side, so the lab can tell inherited changes from ones that arose in the cancer.
- Liquid biopsy
- A blood test that picks up tiny amounts of DNA shed by a tumour. It is a tumour test, even though it uses blood.
- Mismatch repair
- A set of genes that fix copying errors in DNA. Faults in them can guide treatment and point to Lynch syndrome.
- Variant
- A spelling difference in a gene. Only some variants are harmful, and the report says which.
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Side by side
Tumour test or germline test: what does each change?
Tumour test
Germline test
Uses tumour tissue, sometimes blood
Uses blood or saliva
Asks which medicine might work
Asks whether a fault was inherited
Affects the patient's treatment
Affects the patient and the wider family
Ordered by the oncologist
Ordered after genetic counselling
Usually done once per cancer, sometimes repeated
Done once in a lifetime for that question
Commonly believed
Four mix-ups families make between the two tests
"My tumour was tested, so I have had genetic testing."
A tumour test is a genetic test of the cancer, not of you. It does not tell your family whether they share anything. If inherited risk is a question, a separate blood test answers it.
"A BRCA change in my tumour means my children are at risk."
Only if it is also in your blood. Many BRCA changes found in tumours arose in the cancer alone. A blood test tells the two apart before anyone in the family worries.
"The tumour showed nothing, so nothing was inherited."
Tumour tests are built to find treatment targets. Some inherited faults, such as large missing pieces of a gene, can slip past them. Your family history can still justify a germline test.
"A germline result only matters for the family."
It can change your own treatment too. An inherited BRCA fault, for example, can make certain medicines an option and can shape surgery discussions.
Being straight with you
What this page cannot tell you
It cannot tell you whether a change on your tumour report was inherited. Only a blood test, read alongside your family history, can answer that. Your oncologist and a genetic counsellor will explain which changes need that check.
It cannot interpret either report
Tumour and germline reports use the same gene names in different ways. What your specific variant means is a question for the counsellor or oncologist who ordered the test. Please do not forward a tumour report to relatives as though it were about them.
Who this does not apply to
Most people with cancer do not have an inherited fault, and many do not need germline testing at all. If your tumour report raises no germline flag and your family history is unremarkable, a blood test may add nothing. Your care team will say so honestly.
The practical side in India
Two tests usually mean two bills, and insurance or schemes such as Aarogyasri may cover neither. Ask about both costs before either sample is sent. Counselling in Telugu can be arranged.
Holding a tumour report and unsure whether it points to the family? Call the helpline and we will help you find out.Questions we are asked
Common questions about tumour and germline testing
Do I need both tests?
Not always. Many people need only a tumour test to plan treatment. A germline test is added when the cancer type, the tumour result or the family history suggests an inherited cause. Your oncologist and counsellor decide together which you need.
Can one sample be used for both?
Not quite. The tumour test needs tumour tissue or tumour DNA. The germline test needs normal DNA, usually from blood or saliva. Some labs test the two side by side in one order, which makes the comparison cleaner.
My tumour report says a variant may be germline. What now?
It means the change could have been inherited and needs checking in blood. It is not a diagnosis of an inherited fault. Ask your oncologist for a referral to genetic counselling, and do not tell relatives they are at risk until the blood result is back.
Does an inherited fault change my treatment?
It can. Some inherited faults, such as in BRCA1 or BRCA2, make certain targeted medicines an option. They can also affect surgery choices and plans for the other breast or ovaries. Your oncologist will say whether yours does.
Can a tumour test tell my family about their risk?
Not on its own. Changes in a tumour are usually limited to the cancer. Relatives can only be tested usefully once a germline fault has been confirmed in blood. Then each of them can have a simple test for that exact fault.
Who explains the results, and are they given together?
Your oncologist explains the tumour result. A genetic counsellor explains the germline result and what it means for the family. The two results often arrive at different times, so ask each person when to expect theirs.
Is germline testing covered by insurance or schemes?
Coverage for genetic tests in India is patchy. Private policies and government schemes often exclude them, and rules differ between insurers. Ask your insurer in writing before testing, and ask the lab for the full price, counselling included.
Where do I start if I have only a tumour report?
Take the report to your oncologist and ask one question: does anything here need a germline check? If the answer is yes, ask for a genetic counselling referral. Call the CION helpline if you are not sure who to ask.
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 — Biomarker Testing for Cancer Treatment
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
- MedlinePlus Genetics — What is a gene variant and how do variants occur?
- Cancer Research UK — Inherited cancer genes and increased cancer risk
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
Why one test does not replace the otherWhat each test misses when used aloneWhen a tumour result triggers a germline testThe findings that should lead to a blood testHaving both tests at the same timeWhen sending both together saves timeWho orders which testOncologist or geneticist, and who explains what
Talk to us
Does your tumour report point to the family?
Send us the report you have and tell us who in the family had cancer. We will help you work out whether a germline test is worth doing. One helpline serves every CION centre.