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CION Cancer Clinics
Can a genetic test be done from a stored tissue block? | CION Cancer Clinics
Often, yes. A tissue block stored after a biopsy or operation can sometimes be tested for an inherited gene fault, most usefully when the relative who had cancer has died. It is harder than a blood test and does not always work. This page explains when a block is used, how it is arranged, and what can go wrong. At CION Cancer Clinics in Hyderabad, our oncologists review your family history with you and guide you to the right genetic counselling and testing.
NG
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
- Can a genetic test be done from a tissue block?
- When is a tissue block the right sample to test?
- What has to happen to test an old tissue block?
- The words you will meet, in plain language
- A blood sample compared with a tissue block
- What this page cannot tell you
- Four things families assume about tissue blocks
- Common questions about testing a tissue block
The short answer
Can a genetic test be done from a tissue block?
Often, yes. A tissue block stored after a biopsy or surgery can sometimes be used to look for an inherited gene fault. It is most useful when the relative who had cancer has died. It is harder than testing blood, and it does not always work.
What a tissue block is
When tissue is removed during a biopsy or an operation, the pathology laboratory preserves it in a chemical and sets it in a small block of wax. Thin slices are cut from it to make the slides used for diagnosis. Hospitals keep these blocks for a period, so they can still exist long after treatment has finished.
Two very different questions
A block can be tested to learn about the tumour itself, which guides treatment. That is tumour testing, covered on our targeted therapy pages. This page is about the other question: whether the person carried an inherited fault that relatives could share. That needs DNA from the body's normal cells, not just from the cancer.
If the person is alive and can give blood or saliva, that is almost always the better sample.When it is used
When is a tissue block the right sample to test?
Counsellors turn to a block when the best sample, blood from the relative who had cancer, cannot be taken.
The relative has died
This is the most common reason. Testing the person who had cancer tells the family whether there is a fault to look for at all.
Blood cannot be taken
The relative may be too unwell, far away or unwilling to give a new sample, while agreeing that the old block can be used.
A tumour result hints at a fault
Tumour testing sometimes finds a change that could also be inherited. It cannot say which on its own.
- Confirmed with a blood test if the person is alive
- Checked against normal tissue if they are not
When a block is not the answer
If the relative can give blood, use blood. If no block survives, a living relative with cancer or the closest well relative may be tested instead.
Not sure whether this applies to you?
Ask an oncologistHow it is arranged
What has to happen to test an old tissue block?
Find the hospital and the number
You need the name of the hospital where the biopsy or surgery was done, and ideally the pathology number printed on the old report.
Give permission
The patient, or the next of kin if they have died, signs consent to release the block for genetic testing.
The block or slices are released
The pathology department sends the block or thin slices cut from it. Many keep the original block and send only slices.
A pathologist marks the normal tissue
For an inherited question, the laboratory looks for areas without cancer, such as a clear lymph node or a healthy margin.
DNA is extracted and checked
The laboratory first tells you whether the DNA is good enough. If it is not, the test may stop there.
On the paperwork
The words you will meet, in plain language
- Tissue block
- Tissue preserved in chemical and set in wax. Reports may call it an FFPE block, short for formalin-fixed, paraffin-embedded.
- Pathology number
- The reference printed on a biopsy or surgery report. It is the fastest way for a hospital to find the right block.
- Normal tissue
- Parts of the sample that contain no cancer. Its DNA reflects what the person was born with.
- Germline
- A gene change present in every cell from birth, and therefore inheritable.
- Somatic
- A gene change found only in the cancer. It cannot be passed to children.
- DNA quality
- How intact the DNA is. The preserving chemical breaks DNA into short pieces, and older blocks are often worse.
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Side by side
A blood sample compared with a tissue block
Blood or saliva
Stored tissue block
Fresh, good quality DNA
DNA often damaged by preservation and age
Reads every kind of change reliably
Some larger changes may be missed
Always reflects inherited DNA
Needs normal tissue to separate inherited from tumour
Simple to collect from a living person
Needs hospital records, consent and a pathologist
Being straight with you
What this page cannot tell you
It cannot tell you whether your relative's block still exists or will give a usable result. That depends on the hospital, the age of the block and how it was stored. Only the pathology department and the testing laboratory can answer it.
A result from a block needs careful reading
A change found in tissue may belong to the tumour rather than the person. A negative result may reflect poor DNA rather than a true absence. What any result means for your family is a question for the counsellor who ordered the test.
The practical side in India
Retention rules differ between hospitals, and some blocks are lost when a clinic closes. Start with the old report, which carries the pathology number. Ask the laboratory for the full price before the block is sent.
Who this does not apply to
Most families do not need this. If the relative with cancer is alive and can give blood, or if the family history is mild, a block test adds nothing.
Commonly believed
Four things families assume about tissue blocks
"Once the relative has died, the chance to test them is gone."
Not always. A block from an old biopsy or operation may still be stored. It is worth asking the hospital before assuming the answer is lost.
"The tumour test already done tells us if it runs in the family."
A tumour test looks at the cancer. A change it finds may be inherited or may exist only in the tumour. Confirming which needs a separate test on normal cells.
"If the block test is negative, the family is in the clear."
Damaged DNA can hide a fault. Your counsellor will weigh a negative block result against the family history before reassuring anyone.
"The hospital will throw the block away if we ask for it."
Most pathology departments keep the original and send thin slices. Asking does not put the block at risk.
Questions we are asked
Common questions about testing a tissue block
How long do hospitals keep tissue blocks?
It varies between hospitals and laboratories, and there is no single rule you can rely on. Many keep blocks for a long time because they may be needed again. Ask the pathology department directly, with the pathology number if you have it.
Who can give consent if the patient has died?
Usually the next of kin, such as a spouse or an adult child. The hospital will explain its own process and the papers it needs. Your counsellor can help with the request letter.
Can a biopsy block from a small needle biopsy be used?
Sometimes, but small biopsies may contain very little normal tissue. A block from a larger operation, with lymph nodes or healthy margins, is more likely to work. The pathologist will look before the laboratory commits.
Does a tissue block test cost more than a blood test?
Usually, yes. There are retrieval and preparation steps on top of the test, and a failed attempt may still be charged. Ask the laboratory for the full cost in writing before the block is sent.
What if the DNA in the block is too damaged?
The laboratory will say so before running the full test. Your counsellor may then suggest testing the closest living relative who had cancer, or a well relative, and interpreting that result with care.
Can a block from a hospital outside Telangana be used?
Yes, if the hospital agrees to release it. The request is usually made in writing and the block or slices are couriered to the laboratory. It takes longer, so start early.
Will a result from the block be confirmed in relatives?
If a fault is found, relatives are then tested for that exact change using blood or saliva. This also confirms the block result, because a tumour-only change will not appear in relatives.
Where should I start if I think a block exists?
Find the old biopsy or surgery report and note the hospital and the pathology number. Then speak to a genetic counsellor. Call the CION helpline if you are not sure who to approach first.
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
- National Cancer Institute — Biomarker Testing for Cancer Treatment
- National Cancer Institute — Cancer Genetics Risk Assessment and Counseling (PDQ)–Health Professional Version
- 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
Testing a deceased relative's stored sampleAll the kinds of stored sample a family can look forWhich sample type is more reliable?Blood, saliva and tissue comparedGiving the sample: blood, saliva or cheek swabWhat a living person's sample involvesVerifying family cancer history with recordsHow to track down the old reports that lead to a block
Talk to us
Wondering if a relative's old biopsy could still be tested?
Bring whatever reports you have and a counsellor will tell you whether a block test is worth pursuing. One helpline serves every CION centre.