Multiple myeloma (MM) is a cancer that begins in the plasma cells, a type of white blood cell located primarily within the bone marrow. When these cells become malignant, they multiply uncontrollably, crowding out healthy blood-producing cells. A bone marrow biopsy (BMB) is the definitive tool for diagnosis and management. This procedure allows physicians to directly examine the environment where MM originates, providing the precise cellular and genetic information needed for effective treatment planning.
The Necessity of Bone Marrow Biopsy in Multiple Myeloma
Multiple myeloma is defined by the presence of abnormal plasma cells in the bone marrow cavity. Blood tests can suggest the disease, but only a direct sample can confirm the diagnosis by visually identifying the malignant cells. This examination establishes the percentage of cancerous plasma cells, known as the disease burden. This metric is fundamental to distinguishing MM from precursor conditions, such as monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). Active MM typically requires ten percent or more clonal plasma cells in the bone marrow, alongside other disease-defining criteria.
Accurate disease classification and staging rely on the BMB. Staging systems, like the Revised International Staging System (R-ISS), rely heavily on specific genetic markers found in the bone marrow sample to determine the risk profile and overall prognosis. Furthermore, the procedure is used repeatedly to monitor the effectiveness of therapy. By comparing post-treatment biopsies to the initial sample, doctors can assess whether the cancer has gone into remission, relapsed, or if the treatment regimen needs adjustment.
Preparation and Steps of the Procedure
Preparation begins with reviewing current medications, especially blood thinners or NSAIDs, which increase bleeding risk. Physicians advise whether to temporarily stop or adjust these medications. If a mild sedative is used, patients must fast (no food or drink after midnight) and arrange for transportation home afterward.
The procedure is typically performed in an outpatient setting and usually takes less than thirty minutes. The primary collection site is the posterior iliac crest (the back of the hip bone), which contains easily accessible marrow. The patient is positioned on their side or stomach to expose the site, which is then cleaned with an antiseptic solution.
The physician injects a local anesthetic into the skin and down to the bone surface, which may cause a brief stinging sensation. Once numb, a specialized, hollow needle is inserted into the bone. The first step is aspiration, where a syringe quickly withdraws liquid bone marrow. Patients often report a distinct, sharp pain or intense pulling sensation during aspiration, which cannot be completely numbed because the bone itself is sensitive.
Following aspiration, the second step is the biopsy, using a slightly larger needle to obtain a solid core of bone and marrow tissue. The patient will feel pressure and a dull grinding sensation as the physician rotates the needle to secure the sample. Once the aspirate and core specimen are secured, the needles are removed, and firm pressure is immediately applied to the site to control bleeding.
Immediate Post-Procedure Care and Recovery
Immediately after the procedure, pressure is maintained on the site for several minutes, and the patient lies flat for up to fifteen minutes to minimize bruising or bleeding. The site is then dressed with a sterile bandage, which must be kept clean and dry for twenty-four to forty-eight hours. Mild soreness or deep aching at the hip bone is normal and may last for a few days as the anesthetic wears off.
For pain management, patients should take acetaminophen but strictly avoid aspirin or ibuprofen for at least forty-eight hours, as these interfere with blood clotting. Activity restrictions include avoiding strenuous exercise, heavy lifting, or contact sports for the first one to two days. Patients must also avoid submerging the wound in water (no baths, hot tubs, or swimming) for several days, though showering is permitted after twenty-four hours if the dressing is kept dry.
Contact the medical team if complications appear, such as persistent bleeding that soaks through the dressing after applying pressure for fifteen minutes, or signs of infection. Infection signs include fever, increasing redness, swelling, or excessive drainage from the biopsy site. New or persistent numbness or weakness in the leg also warrants immediate medical attention.
Understanding the Bone Marrow Biopsy Results
The bone marrow sample is processed for several complex laboratory analyses, each providing different information about the disease. The first finding is the plasma cell percentage, determined by a pathologist counting cells under a microscope to confirm diagnosis and disease burden. Normal bone marrow contains less than five percent plasma cells, so any significant increase indicates a plasma cell disorder.
Flow cytometry is performed on the liquid aspirate to identify the immunophenotype of the plasma cells using specific surface markers. Malignant plasma cells typically express markers like CD38 and CD138, confirming they are a clonal population. This molecular signature helps track the disease and informs the use of targeted therapies.
Cytogenetics and Fluorescence In Situ Hybridization (FISH) testing examine the chromosomes within the malignant plasma cells. Chromosomes are analyzed for abnormalities such as deletions (a missing piece) or translocations (switched pieces). These genetic changes are paramount in determining the patient’s prognosis, as certain abnormalities define the disease as high-risk or standard-risk.
For example, a deletion on chromosome 17 (del 17p) or a translocation between chromosome 4 and 14 (t(4;14)) are high-risk features indicating a more aggressive disease course. The results of this genetic analysis are integrated with other clinical factors to assign the patient a stage using systems like the R-ISS. This staging then guides the intensity and type of initial treatment, providing the foundation for personalized multiple myeloma care.