Bone Marrow Biopsy

Bone marrow is the soft, spongy tissue inside larger bones that produces red cells, white cells and platelets. When blood tests show too many, too few or abnormal cells, examining the marrow directly often explains why. A bone marrow biopsy usually includes two parts. The aspirate is a small amount of liquid marrow drawn up through a needle; it is spread on slides to study the shape and proportion of developing cells, and sent for flow cytometry, which identifies cell types by markers on their surface, and for genetic tests such as cytogenetics, FISH and molecular sequencing. The trephine is a thin core of bone with marrow, about 1 to 2 centimetres long, which shows how full the marrow is, its structure and any infiltration by abnormal cells or scarring. The usual site is the back of the pelvis, called the posterior iliac crest, because the bone there is close to the skin and away from major organs. The breastbone is used occasionally for an aspirate only in adults.

A bone marrow biopsy is recommended when blood tests or other findings suggest a problem with blood cell production that cannot be explained by simpler tests. Common reasons include unexplained low counts of red cells, white cells or platelets, abnormal cells in the blood film, and suspected acute or chronic leukaemia. It is used to diagnose myelodysplastic syndrome, aplastic anaemia and myeloproliferative disorders such as myelofibrosis, and to assess multiple myeloma and related conditions in which abnormal plasma cells or proteins are found. In lymphoma it may be done to see whether the marrow is involved, although PET-CT scanning now replaces it in some types. After diagnosis it is repeated to judge response to chemotherapy or targeted treatment, to look for minimal residual disease, and before and after a stem cell transplant or CAR-T cell therapy. Less commonly it is used to investigate a fever of unknown cause, some infections or storage disorders.

You lie on your side with your knees drawn up, or on your front. The doctor or specialist nurse feels for the bony ridge at the back of the hip, cleans the skin and injects local anaesthetic into the skin and down to the surface of the bone, which stings briefly. If you choose sedation, it is given through a cannula in the arm before this. A small nick is made in the skin. For the aspirate, a hollow needle is pushed through the outer layer of bone and a syringe draws up the liquid marrow; this produces a short, deep pulling sensation that lasts a few seconds. For the trephine, a slightly wider needle is advanced with a twisting motion to cut a thin core, which brings pressure and an ache. The needle is removed, firm pressure is applied for several minutes, and a dressing is placed. You lie on your back for a short time to help stop any bleeding. The procedure usually takes about 20 to 30 minutes.

Almost anyone who needs a bone marrow diagnosis can have the procedure, including children, who usually have it under general anaesthesia or deeper sedation. Before the test your team reviews your blood counts and clotting. If your platelet count is very low, a platelet transfusion may be given beforehand, and blood thinners may need to be paused on medical advice. Tell the team about allergies, especially to local anaesthetic or antiseptic, and about any previous problems with sedation. If you are having sedation, you may be asked not to eat for a few hours beforehand and must arrange for someone to take you home, as you should not drive for 24 hours. Otherwise you can eat normally. International patients should send recent blood test results, blood films, scans and any previous marrow reports in advance, so the haematologist can decide which laboratory tests to request and avoid repeating the procedure because a test was missed.

After the procedure you rest for about 30 minutes to an hour, longer after sedation, and the dressing is checked before you leave. Keep the dressing dry and in place for about 24 hours, after which you can shower. The site may ache and bruise for a few days, and paracetamol is usually enough; your team may advise avoiding some anti-inflammatory painkillers if your platelets are low. Most people return to normal activities the next day, but avoid strenuous exercise, swimming and heavy lifting for a day or two. Flying is generally fine the next day. The main planning question is waiting for results. Initial findings from the aspirate can be ready within days, the trephine report usually takes about a week, and genetic and molecular results about two weeks. Many people therefore stay for the first results and then receive the full report remotely, with treatment planned once all the information is available.

A bone marrow biopsy is a common and safe procedure. Pain during sampling is usually brief, and soreness at the site for a few days is expected. Bruising is common. Bleeding that persists or forms a large collection is uncommon and is more likely in people with very low platelets or clotting problems, which is why these are checked and corrected beforehand. Infection at the site is rare. Very rarely, the needle passes through the bone and damages nearby structures; this is extremely unusual at the hip. With sedation there is a small risk of breathing being suppressed, which is monitored throughout. The results describe how full the marrow is, the proportions and appearance of developing blood cells, any abnormal or cancer cells and their percentage, any scarring, iron stores and, from genetic tests, specific chromosome changes or mutations. Together they confirm or exclude a diagnosis, classify the disease and help predict how it will behave and respond to treatment.