Medical Oncologist
Biomarker & Molecular Testing
Can Mutation Testing Be Done on — an Old Biopsy Block?
Yes — laboratories can run NGS on archived biopsy blocks, sometimes years after the original procedure. Whether testing succeeds depends on the tissue quality inside the block, not the date on the label.
Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed August 2026
- Old does not mean unusable — Paraffin-embedded tissue preserves DNA for years. Age alone is not the deciding factor.
- The lab checks quality first — A DNA quality check runs before the full panel, so a failing block does not cost you the price of a complete test.
- Slides can substitute for a block — Unstained sections cut from the original block are acceptable when the block itself is unavailable.
- Alternatives exist if tissue fails — Liquid biopsy and re-biopsy are the options your team will discuss if the old sample cannot be used.
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Yes, NGS can be done on an old biopsy block or unstained slides. Whether the test gives a usable result depends on tissue age, how it was fixed and stored, and how much tumour is present in the sample. Your oncologist will ask the laboratory to assess the block before committing to a full panel.
Can a laboratory actually use tissue from years ago?
Biopsy tissue is routinely preserved in formalin and embedded in paraffin wax — a format called FFPE. This method has been standard in Indian pathology laboratories for decades, and its purpose is exactly this: to keep tissue stable for future use.
The DNA inside an FFPE block does degrade over time. What matters more than age alone is how the tissue was fixed in the first place, how long fixation took, and how the block has been stored since. A well-fixed block kept in controlled conditions can yield DNA suitable for NGS many years later.
Tumour cellularity also matters. The laboratory needs enough tumour cells — not just surrounding normal tissue — to extract sufficient DNA for sequencing. A block that is mostly scar tissue or inflammation may not provide enough material, even if the DNA itself is largely intact.
Every laboratory runs a quality check on the extracted DNA before starting a full panel. This step tells the team whether testing can proceed, and it protects you from paying for a complete test on a sample that cannot give a reliable result.
What happens if my old biopsy sample fails the quality check?
If the block passes quality check, testing proceeds and your team will give you a turnaround estimate from that point. If the block fails, the next step is usually to try unstained slides cut from the same block — slides carry less DNA, so the laboratory may request several sections to gather enough material.
If slides also fail, or are not available, your oncologist will discuss two alternatives. A new biopsy from the current tumour provides fresh tissue and has the added advantage of reflecting how the disease looks now rather than at an earlier point in time.
Liquid biopsy — a blood draw that detects tumour DNA circulating in the bloodstream — is an option when the tumour cannot be safely reached again. It is not equally sensitive for all mutations and is not suitable for every cancer type, so your oncologist will advise whether it answers the specific clinical question being asked.
Being told the old block has failed is not the end of the road. It is information that moves the decision toward the option most likely to give a usable result.
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Block, slides, or blood — which sample should you send?
| FFPE block (archived) | Unstained slides | Liquid biopsy (blood) | |
|---|---|---|---|
| What it is | Original biopsy tissue preserved in paraffin wax | Thin sections cut from the FFPE block | A blood draw testing for tumour DNA shed into the bloodstream |
| Needs a new procedure | No | No | No — a routine blood draw |
| Best suited to | Standard NGS panels for most solid tumours; the first choice when available | When the block is held by another hospital or only sections were archived | When tumour tissue cannot be safely obtained or re-biopsied |
| Main limitation | DNA quality varies with age and fixation; must pass a quality check before testing begins | Fewer sections available; quality still depends on how the original block was prepared | Lower sensitivity for some mutations; not equally informative for all cancer types |
| If the sample fails | Slides or liquid biopsy discussed with your oncologist | Original block requested, or liquid biopsy considered | Usually still gives a result, though some mutations may not be detectable |
Did you know?
Formalin-fixed, paraffin-embedded tissue — the format your biopsy block is stored in — was designed to preserve tissue for exactly this purpose.
Major molecular testing guidelines from ESMO and the College of American Pathologists accept it as the standard input for comprehensive tumour profiling, including multi-gene NGS panels.
Source: ESMO Precision Medicine Working Group; College of American Pathologists (CAP) molecular pathology guidelines
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Common questions
Frequently asked questions
How old can a biopsy block be and still work for NGS?
A block from many years ago can still yield usable DNA — there is no fixed year beyond which testing cannot proceed. What matters more than age is how the tissue was fixed at the time of the biopsy and how it has been stored since. A well-fixed, well-stored block can give good results; some more recent blocks fail because fixation time was too short or too long. The laboratory quality check is the only reliable way to assess your specific sample. Your team will request the block and report back once that assessment is complete.
What is the difference between sending the block and sending slides?
The block is the original paraffin-embedded tissue; slides are thin sections cut from it. The block contains substantially more DNA and is the preferred material. Slides are used when the block is unavailable — held by another hospital, for example — or when only sections were archived. If slides are sent, the laboratory will specify how many sections it needs. Fewer sections may limit which panels can be run, particularly larger multi-gene panels that require more starting material.
My biopsy block is at a hospital in another city. How do I get it transferred?
The block belongs to you, and you are entitled to request it or a copy of the unstained slides from the hospital that holds it. Most hospitals in India will release the block or cut fresh sections on written request, sometimes with a small processing fee. Your oncology team or a CION coordinator can help you draft the request letter and specify exactly what format the receiving laboratory needs. Courier of FFPE blocks between cities is routine — the material is stable in transit at room temperature.
If the old block fails the quality check, do I have to have another biopsy?
Not necessarily. A new biopsy is one option, but it is not always needed or possible. If unstained slides from the same block have not been tried, the laboratory may request those first. Liquid biopsy — a blood draw — is the alternative when the tumour cannot be reached safely or when your current condition makes a new procedure inadvisable. Your oncologist will weigh which option is most likely to give an actionable result in your specific situation.
How long does mutation testing on an old biopsy block take?
Testing from an FFPE block typically takes a little longer than testing from fresh tissue, because the quality check adds a step before the panel begins. Your team will give you an expected turnaround once the laboratory has confirmed whether the block is suitable. If the block fails and a new sample is needed, the timeline resets from the point the new sample is received. Asking your team for an estimated turnaround at the time the block is dispatched helps you plan around the wait.
Will molecular testing on an old block be covered by insurance or a government scheme?
Coverage for molecular testing in India varies by insurer, policy, and cancer type, and the rules change regularly. Some government schemes — including Ayushman Bharat — cover selected diagnostic tests, but coverage for comprehensive NGS panels is not universal. Ask your oncology team to provide the correct diagnostic codes before the test is ordered, and ask your insurer in writing whether prior authorisation is required. A CION coordinator can advise on the documentation typically needed to support a reimbursement claim.