Bone Marrow Aspiration and Bi... Health Article

Definition

Bone marrow aspiration, also called bone marrow sampling, is the removal by suction of the soft, spongy semisolid tissue (marrow) that fills the inside of the long and flat bones. Bone marrow biopsy, or needle core biopsy, is the removal of a small piece (about 0.75 X 0.06 in, or 2 X 0.16 cm) of intact bone marrow. The bone marrow is where blood cells are made.

Purpose

Examination of the bone marrow may be the next step that follows an abnormal clinical finding, such as an abnormal complete blood count (CBC), and/or an abnormal peripheral blood smear. It may also be performed following an abnormal bone image such as the finding of a lesion on x rays.

A biopsy of bone marrow shows the intact tissue, so that the structure of the fat cells, lymphocytes, plasma cells, fibrous connective tissue cells, and other cells, and their relationships to each other, can be seen. A bone marrow biopsy is used to:

• diagnose and manage any form of leukemia or other myeloproliferative condition such as multiple myeloma
• rule out or confirm bone marrow infiltration by malignancies such as Hodgkin's disease, non-Hodgkin's lymphoma, and metastatic carcinoma
• monitor the effects of chemotherapy and the response or lack of response to treatment of blood disease
• evaluate the success of bone marrow transplantation
• diagnose certain genetic diseases (e.g., lipid storage disease)
• investigate pancytopenia (a decrease of all blood cells in peripheral blood), neutropenia (decreased phagocytic white blood cells), or thrombocytopenia (decreased platelets)
• diagnose an infection of unknown origin
• investigate rare anemias for which a cause cannot be found or which does not respond to treatment as anticipated
• obtain intact bone marrow for laboratory analysis
• diagnose some types of cancer or anemia and other blood disorders
• identify the source of an unexplained fever (e.g., granulomatous lesions)
• diagnose fibrosis of bone marrow and myeloma when bone marrow aspiration has failed to provide an appropriate specimen

The combination of aspiration and biopsy procedures are commonly used to ensure the availability of the best possible bone marrow specimen. The aspirate is collected at the same time as the bone core biopsy by attaching a syringe to the bone marrow needle and withdrawing the sample before the cutting blades are inserted and the bone core is removed. The aspirate is the sample of choice for studying and classifying the nucleated blood cells of the bone marrow (e.g., determining the ratio of immature white blood cells to red blood cells (M:E ratio). The biopsy is the only sample that shows the blood forming cells in relation to the structural and connective tissue elements (i.e., the microarchitecture) of the bone marrow. It provides the best sample for evaluating the cellularity of the bone marrow (the percentage of blood-forming tissue versus fat).

Description

Bone marrow aspiration and biopsy are performed by a pathologist, hematologist, or oncologist with special training in this procedure. The procedure may be performed on an outpatient basis. In adults, the specimen is usually taken from the posterior superior iliac crest (hip). The sternum (breastbone) may be used for aspiration, but is less desirable because it carries the risk of cardiac puncture. Other sites that are rarely used are the anterior superior iliac crest or a spinal column bone. When the patient is a child, the biopsy site is generally the anterior tibia, the larger of the two bones in the lower leg. A vertebra may also be used.

The skin covering the biopsy site is cleansed with an antiseptic, and the patient may be given a mild sedative. The patient is positioned, and a local anesthetic such as lidocaine is administered first under the skin with a fine needle and then around the bone at the intended puncture site with a somewhat larger gauge needle. When the area is numb, a small incision is made in the skin and the biopsy needle is inserted. Pressure is applied to force the needle through the outer bone, and a decrease in resistance signals entry into the marrow cavity. The needle most often used for bone marrow biopsy is a Jamshidi trephine needle or a Westerman-Jensen trephine needle. A syringe is placed on the top of the needle and 1–2 ml of the bone marrow is aspirated into the syringe. In some instances, the marrow cannot be aspirated because it is fibrosed or packed with neoplastic cells. The syringe is removed and the medical technologist uses this sample to prepare several smears containing small pieces of bone (spicules). Another syringe is fitted onto the needle hub and another sample of 3 ml is removed and transferred to a tube containing EDTA for analysis by flow cytometry, cytogenetic testing, or other special laboratory procedures. Following aspiration, the cutting blades are inserted into the hollow of the needle until they protrude into the marrow. The needle is then forced over the tips of the cutting blades and the needle is rotated as it is withdrawn from the bone. This process captures the core sample inside the needle. A wire probe is inserted at the cutting end and the bone marrow sample is pushed through the hub of the needle onto sterile gauze. The specimen is used to make several preparations on glass slides or coverglasses and is transferred to a fixative solution.

In the laboratory, the aspirate slides are stained with Wright stain or Wright-Giemsa stain. The biopsy material is sectioned onto glass slides and stained with hematoxylin-eosin, Giemsa, and Prussian blue stains. Prussian blue stain is used to evaluate the amount of bone marrow iron, and the other stains are used to contrast cell structures under the microscope. In addition, special stains may be used that aid in the classification of malignant white blood cells.