Hematologist
CION Cancer Clinics
Where your bone marrow slides and blocks are stored | CION Cancer Clinics
Your bone marrow slides and paraffin blocks stay in the archive of the pathology lab that reported your test, not with your doctor and not with you. Slides and blocks are generally kept far longer than liquid samples, but every lab sets its own policy. This page explains what is stored, what to write down now, and how to ask for the material to be released for a second opinion. At CION Cancer Clinics, our haematologist reviews abnormal blood reports with you, orders only the tests that answer your question and explains each result plainly.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- Where are your bone marrow slides and blocks actually kept?
- What exactly is stored after a bone marrow test?
- How does your marrow sample end up in storage?
- What should you write down while it is still easy?
- What do families often assume about slides and blocks?
- Which words will the lab use when you ask?
- How do you ask for them, and what can go wrong?
- Common questions about marrow slide and block storage
The short answer
Where are your bone marrow slides and blocks actually kept?
They stay in the archive of the pathology lab that processed your bone marrow test. They are not with the doctor who did the procedure, and they are not usually handed to you. You can ask the lab to release them for a second opinion.
Why the lab keeps them
Slides and tissue blocks are the original evidence behind your diagnosis. The report is only a summary of what a pathologist saw on them. Keeping the material lets the lab look again if a question comes up, lets another expert review the same cells, and lets extra tests be run later without a new marrow procedure.
How long they are kept
Retention rules differ between labs and between types of material. Stained glass slides and paraffin blocks are generally kept for years. Fresh liquid samples and leftover tubes are usually discarded much sooner, because they do not last. This page cannot tell you your own lab's policy. Ask the lab directly, and ask early.
If your diagnosis was made at a hospital or lab that has since closed or merged, ask the new owner where the archive went.What is in the archive
What exactly is stored after a bone marrow test?
A single marrow test produces several kinds of material. Each one is kept differently and is useful for different things.
Aspirate smears
Liquid marrow spread thinly on glass and stained. These show the shape and maturity of individual cells. Stained smears are fragile and can break or fade, so labs handle them with care.
The trephine block
The small core of bone, softened, set in paraffin wax and stored as a block. This is the most valuable item, because thin new slices can be cut from it for extra stains or tests.
Worth knowing
- Each new slice uses up tissue
- A small core can run out
Biopsy and special stain slides
Slides cut from the block, including IHC slides. IHC, or immunohistochemistry, is a stain that shows which proteins the cells carry. These are what a reviewing pathologist looks at first.
Data and extracts
Flow cytometry data files, and sometimes DNA or RNA taken out for genetic tests. Whether these are kept, and for how long, varies most from lab to lab.
Leftover liquid marrow is rarely usable later.Not sure whether this applies to you?
Ask an oncologistFrom the bed to the archive
How does your marrow sample end up in storage?
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The procedure
Liquid marrow and a small core of bone are taken from the back of the hip bone. Some of the liquid is spread on slides at the bedside. The rest goes into tubes for other tests.
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Labelling and logging
The lab gives the sample a unique number, often called an accession or lab number. Every slide and block carries it. This number is the key to finding your material later.
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Processing
The core is softened, set in wax and sliced. Slides are stained, sometimes with extra stains once the first look raises questions.
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Reporting
A pathologist or haematologist reads the slides and signs the report. Tubes may be sent on to other labs for flow cytometry or genetic tests.
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Filing
Slides go into labelled slide cabinets and blocks into block drawers, kept dry, at room temperature and away from heat. Records link each item back to your name and lab number.
Do this now
What should you write down while it is still easy?
- The full name and address of the lab that reported the marrow
- The accession or lab number printed on the report
- The date the procedure was done
- Whether flow cytometry or genetic tests went to a different lab
- The name of the doctor who requested the test
- A clear photo or scan of every page of each report
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
Commonly believed
What do families often assume about slides and blocks?
"The report is all we need for a second opinion."
A report tells another doctor what one person saw. For a blood cancer diagnosis, a proper second opinion usually means looking at the actual slides, and sometimes cutting new ones from the block. The report alone may not be enough.
"The slides belong to the hospital, so we cannot get them."
Labs look after the material, but they routinely release slides and blocks for review when a patient or treating doctor asks in writing. Some keep one set back and send recut or duplicate slides instead. Ask what their process is.
"Blocks last forever, so there is no hurry."
Blocks are stable, but labs do clear old archives in line with their policy. Every extra test also uses tissue. If a review is likely, request the material early and ask the lab not to discard it.
"If the block is lost, the diagnosis cannot be checked."
Stained slides, flow data or genetic results can still support a review. Sometimes a repeat marrow test is needed, and your haematologist will explain why before asking you to have one.
Lab language
Which words will the lab use when you ask?
- Accession number
- The lab's unique number for your sample. Quote it in every request.
- Aspirate
- The liquid part of the marrow, drawn up with a needle and spread on slides.
- Trephine biopsy
- The thin core of bone and marrow taken in the same procedure.
- Paraffin block
- Tissue set in wax so it can be sliced thin and stored.
- Recuts or unstained slides
- Fresh slices cut from your block, sent so another lab can run its own stains.
- Slide review
- A second pathologist or haematologist looking at your existing slides, without a new procedure.
Being straight with you
How do you ask for them, and what can go wrong?
Write to the lab, or ask your treating doctor to write. Give your name, date of birth, the accession number, the date of the procedure and where the material should go. Most labs will ask for your signed consent and an identity document, and may charge a small handling fee.
What can go wrong
Slides can crack in the post. Blocks can run thin after several rounds of testing. Material can be sent to the wrong address when the request is vague. Ask the lab to pack slides in a proper slide mailer, to keep a record of what was sent, and to tell you when it has been dispatched.
What CION does and does not do
CION's haematology team can request your existing slides and blocks, arrange a review with a qualified laboratory, and present your case at a tumour board. CION does not claim to process marrow samples in-house. The team will tell you plainly whether a review is enough or a repeat test is needed.
This page cannot tell you whether your first diagnosis was right. Only a review of the material can.Questions we are asked
Common questions about marrow slide and block storage
Can I keep my own bone marrow slides at home?
It is not a good idea, and many labs will not release them to a patient directly. Glass slides break, stains fade in heat and light, and home storage has no record of what the items are. It is safer to ask the lab to send them straight to the reviewing lab or doctor.
Who can ask the lab to release my slides?
You can, and so can your treating doctor. For a child, a parent or guardian signs. If the patient is too unwell, the lab may accept a request from a close family member with written consent or a doctor's letter. Ask the lab which documents it needs before you travel there.
Will the lab send the original block?
Some labs send the block and ask for it back. Others keep the block and send freshly cut unstained slides instead, so the original stays safe. Both are normal. Tell the lab what tests the reviewing team wants, so it sends enough material in the right form.
My marrow test was done a long time ago. Is the material still there?
Possibly. Glass slides and paraffin blocks are usually kept far longer than liquid samples, but each lab sets its own policy. Call the lab with the accession number and date. If they have cleared that archive, ask whether any flow data or genetic results remain on file.
Does sending slides away delay my treatment?
A review adds some time for packing, courier and reading. Your haematologist weighs that against how urgent treatment is. When treatment cannot wait, it may start while the review is under way. Please do not hold back or stop any treatment yourself while you wait for a second opinion.
What if the lab refuses or does not reply?
Put the request in writing and keep a copy. Ask your treating doctor to request the material on letterhead, which labs usually act on faster. If there is still no reply, ask the hospital's medical records or patient relations office to help trace it.
Is there a cost to get slides and blocks released?
Many labs charge a handling or recut fee, and the courier has a cost too. The review itself is billed separately. Scheme and insurance cover for these charges varies, including under Aarogyasri, CGHS, ECHS, EHS and PM-JAY, so check your current rules first.
Can slides be sent safely to another city?
Yes, when they are packed properly. Slides travel in rigid slide mailers with padding, and blocks in sealed containers kept away from heat. Use a courier that tracks the parcel, and ask both labs to confirm dispatch and arrival so nothing goes missing between them.
Your Haematologist
Meet CION's haematologist. One specialist for your blood report and your plan.
Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Sources
- NHS — Bone marrow biopsy
- Cancer Research UK — Bone marrow test
- National Cancer Institute — Pathology Reports
- American Cancer Society — Tests and procedures for cancer
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
Getting Slides Released for a Second OpinionThe step-by-step request, once you know where the slides areRepeat Testing vs Re-Reviewing Existing SlidesWhen stored material can spare you another marrow testSending Samples Outside Your CityHow to move slides and samples safely between labsHaematology Lab and Pathology QualityThe full guide to lab quality in blood disorders
Talk to us
Want your marrow slides reviewed?
Tell us which lab reported your bone marrow test. CION's haematology team will explain how to request the slides and arrange a review. One helpline serves every CION centre.