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Your archived tissue

How Long Are Biopsy Blocks — and Slides Kept?

Your biopsy block is a permanent record of your tumour tissue. Knowing where it is, and for how long it will be kept, matters — because new molecular tests may need it years from now.

Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed September 2026

  • A block, not just a report — Your pathology report describes what the block shows. The block itself is what makes future testing possible.
  • Accreditation sets the minimum — NABH-accredited labs are required to retain blocks for a defined period. That period is a floor, not a ceiling.
  • Slides last less long — Glass slides are more fragile and have a shorter minimum retention period than paraffin blocks.
  • Retrieval is your right — You can request your blocks back — for a second opinion, a new test, or transfer to another centre.
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Biopsy blocks — paraffin-embedded tissue from your biopsy — are kept by NABH-accredited labs for a minimum period set by their accreditation standards. Blocks last far longer physically. They can be retrieved years later for a second opinion, repeat molecular testing, or clinical trial eligibility. Glass slides have a shorter minimum retention period than blocks.

How long are biopsy blocks kept in India?

NABH accreditation standards set a minimum retention period for paraffin-embedded tissue blocks held by accredited hospitals and pathology labs. The minimum is measured in years, and the current figure is stated in the NABH accreditation documents for histopathology services.

Glass slides are more fragile and are typically kept for a shorter minimum period. If your report is from a biopsy done several years ago, the block is more likely to still be available than the original cut slides.

The minimum retention period and the physical lifespan of a block are different things. Paraffin-embedded tissue stored in a cool, dry environment can remain suitable for molecular testing decades after the original biopsy — well beyond any regulatory minimum.

Can blocks be retrieved years after your diagnosis?

Yes, provided the retention period has not passed. The most common reasons to retrieve a block are a second-opinion pathology review, new biomarker or gene panel testing, and eligibility assessment for a clinical trial.

Some molecular tests — including certain gene sequencing panels and predictive biomarker assays — were not available when many patients were first diagnosed. An archived block means those tests can be run retrospectively without putting you through a new biopsy procedure.

If the lab that did your biopsy has since closed or merged, the blocks should have been transferred to the successor institution or to a designated repository. Ask rather than assume they are lost — they often are not.

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How to retrieve your biopsy block

  1. Find your original pathology report

    The report names the lab and carries a report number or accession number. Both are needed for the retrieval request. If you do not have a copy, your treating oncologist's records should hold one.

  2. Write a formal request to the pathology department

    Address it to the head of pathology at the originating lab. Include your full name, the report number, the approximate date of the biopsy, and the reason you are requesting the material.

  3. Attach identity proof and your doctor's letter

    Most labs require an authorisation letter from your oncologist as well as a copy of your identity document before releasing blocks for external transfer.

  4. Confirm collection or courier arrangements

    Blocks are sent in a padded container with a chain-of-custody note. Ask the lab whether they use courier or require in-person collection, and whether a handling fee applies.

  5. Insist on the block's return after testing

    A block is a permanent archive, not a consumable. When sending it to another lab for a second cut or additional testing, confirm in writing that the block will be returned to the originating lab after testing is complete.

What to track from the day of your biopsy

  • Write down the full name and address of the lab that processed each biopsy.
  • Save every pathology report, including the accession number printed at the top.
  • Ask your oncologist whether a paraffin block was made, or only slides — this matters for future testing.
  • If you change hospitals or cities, ask about your blocks explicitly; they are not always transferred automatically.
  • If a lab sends your block elsewhere for testing, confirm in writing that it will be returned.
  • If you hear that a lab is closing, request your blocks promptly rather than waiting to see what happens.

Did you know?

Paraffin-embedded tissue blocks are among the most durable biological archives in medicine. Blocks from biopsies done decades ago have been used to run gene sequencing tests that did not exist at the time of the original biopsy.

The archive exists so that future medicine can ask questions that today's medicine has not yet learned to ask.

Source: ICMR Guidelines on Pathological Material and Tissue Banking

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Common questions

Frequently asked questions

What happens if the lab has already discarded my blocks?

If the retention period has passed and the lab no longer holds your block, the material is gone and cannot be recovered. This matters most when a new molecular test becomes relevant — gene panel sequencing, for instance — or when you are being assessed for a clinical trial that requires tissue confirmation. In those cases, your oncologist will discuss whether a new biopsy from an accessible site is feasible, or whether a liquid biopsy can answer the same question. This is one reason to confirm your block's location proactively rather than waiting until a test is needed.

Can I take my blocks to another hospital for a second pathology opinion?

Yes. Requesting your blocks for a second-opinion review is a recognised and common practice. You will need a formal request letter, usually countersigned by your oncologist, and the receiving lab must agree to return the block once the review is complete. The originating lab retains the right to hold the block for its minimum retention period, so coordinate directly with both labs rather than assuming the transfer is automatic. Ask your oncologist's team whether they can coordinate the request on your behalf — many oncology centres handle this routinely.

Are slides as useful as blocks for molecular testing?

For most molecular and genetic tests — including gene panel sequencing, FISH, and PCR-based assays — the paraffin block is preferred because it contains more tissue and allows fresh sections to be cut as needed. Slides can be used when a block is not available, but they carry less material and some tests cannot be run from slides alone. If you are told that only slides are available and you need molecular testing, ask your oncologist whether the available material will be sufficient for the specific test being requested.

What if the lab that processed my biopsy has closed down?

When a NABH-accredited lab closes, its pathological material — including blocks — should be transferred to a successor institution or held by a designated custodian, in line with accreditation requirements. Start by contacting the hospital where the biopsy was originally done; they will have a record of where the pathology was sent. If a private lab closed independently, contact NABH or ask your treating oncologist to help trace the material. It is worth pursuing rather than assuming the blocks are lost.

Is there a charge to retrieve my blocks?

Many accredited labs charge a handling or administrative fee for retrieving and packaging blocks for external transfer. The amount varies between institutions and there is no standard national fee. Before arranging retrieval, ask the lab directly whether a fee applies and what it covers. The fee, where it exists, is typically modest relative to the cost of repeating a biopsy procedure. Confirm the arrangement in writing so there is no dispute about return conditions once testing is complete.

Full index

Browse all 701 biopsy topics

Every page in this section, grouped by the part of the journey it belongs to. Pick a group to see what is in it.

What Is a Biopsy?

What Is a Biopsy? Everything You Need to Know →

Types of Biopsy Compared

Which Biopsy Will You Have? Techniques Compared →

Preparing for a Biopsy

What to Expect on the Day of Your Biopsy →

Recovery and Aftercare

After a Biopsy: Recovery, Aftercare and Warning Signs →

Biopsy by Body Part

Biopsy by Body Part: What to Expect at Each Site →

Understanding Your Report

How to Read a Biopsy Report: Terms Explained →

IHC and Molecular Markers

IHC and Molecular Markers on a Biopsy: What They Mean →

Grading and Scoring Systems

Cytology & Prostate Scoring Systems Explained →

How Accurate Is a Biopsy?

How Accurate Is a Biopsy? Errors and Second Opinions →

If Your Result Is Benign

Your Biopsy Is Benign: What It Means and What Comes Next →

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