Case Study

A patient came for treatment complaining of weakness, fatigue, and malaise. Complete blood count results were as follows:

Bone marrow was hypercellular with 90% myeloid precursors and 10% erythroid precursors. There were 15 megakaryocytes per 10× objective field.

Bone Marrow Anatomy and Architecture

In adults, bone marrow accounts for 3.4% to 5.9% of body weight, contributes 1600 to 3700 g or a volume of 30 to 50 mL/kg, and produces roughly six billion blood cells per kilogram per day in a process called hematopoiesis.¹ At birth, nearly all the bones contain red hematopoietic marrow (see Chapter 7). In the fifth to seventh year, adipocytes (fat cells) begin to replace red marrow in the long bones of the hands, feet, legs, and arms, producing yellow marrow, and by late adolescence hematopoietic marrow is limited to the lower skull, vertebrae, shoulder, pelvic girdle, ribs, and sternum (see Figure 7-2). Although the percentage of bony space devoted to hematopoiesis is considerably reduced, the overall volume remains constant as the individual matures.² Yellow marrow reverts to hematopoiesis, increasing red marrow volume, in conditions such as chronic blood loss or hemolytic anemia that raise demand.

The arrangement of red marrow and its relationship to the central venous sinus is illustrated in Figure 7-3. Hematopoietic tissue is enmeshed in spongy trabeculae (bony tissue) surrounding a network of sinuses that originate at the endosteum (vascular layer just within the bone) and terminate in collecting venules.³ Adipocytes occupy approximately 50% of red hematopoietic marrow space in a 30- to 70-year-old adult, and fatty metamorphosis increases approximately 10% per decade after 70.⁴

Indications for Bone Marrow Examination

Because the procedure is invasive, the decision to collect and examine a bone marrow specimen requires clinical judgment and the application of inclusion criteria. With the development of cytogenetic chromosome studies, flow cytometry, immunohistochemistry, and molecular diagnostics, peripheral blood may often provide information historically available from bone marrow only, reducing the demand for marrow specimens. On the other hand, these techniques also augment bone marrow–based diagnosis and thus potentially raise the demand for bone marrow examinations in assessment of conditions not previously diagnosed through bone marrow examination.

Table 16-1 summarizes indications for examination of bone marrow.⁵ Bone marrow examinations may be used to diagnose and stage hematologic and nonhematologic neoplasia, to determine the cause of cytopenias, and to confirm or exclude metabolic and infectious conditions suspected on the basis of clinical symptoms and peripheral blood findings.⁶

Bone Marrow Specimen Collection Sites

Bone marrow specimen collection is a collaboration between a medical laboratory scientist (medical technologist) and a skilled specialty physician, often a pathologist or hematologist.⁷ Prior to bone marrow collection, the medical laboratory scientist collects peripheral blood for a complete blood count with blood film examination. During collection, the scientist assists the physician by managing the specimens and producing initial preparations for examination.

Red marrow is gelatinous and amenable to sampling. Most bone marrow specimens consist of an aspirate (obtained by bone marrow aspiration) and a core biopsy specimen (obtained by trephine biopsy), both examined with light microscopy using 100× and 500× magnification. The aspirate is examined to identify the types and proportions of hematologic cells and to look for morphologic variance. The core biopsy specimen demonstrates bone marrow architecture: the spatial relationship of hematologic cells to fat, connective tissue, and bony stroma. The core biopsy specimen is also used to estimate cellularity.

The core biopsy specimen is particularly important for evaluating diseases that characteristically produce focal lesions, rather than diffuse involvement of the marrow. Hodgkin lymphoma, non-Hodgkin lymphoma, multiple myeloma, metastatic tumors, amyloid, and granulomas produce predominantly focal lesions. Granulomas, or granulomatous lesions, are cell accumulations that contain Langerhans cells—large, activated granular macrophages that look like epithelial cells. Granulomas signal chronic infection. The biopsy specimen also allows morphologic evaluation of bony spicules, which may reveal changes associated with hyperparathyroidism or Paget disease.⁸

Bone marrow collection sites include the following:

• Posterior superior iliac crest (spine) of the pelvis (Figure 16-1). In both adults and children, this site provides adequate red marrow that is isolated from anatomic structures which are subject to injury. This site is used for both aspiration and core biopsy.

• Anterior superior iliac crest (spine) of the pelvis. This site has the same advantages as the posterior superior iliac crest, but the cortical bone is thicker. This site may be preferred for a patient who can only lie supine.

• Sternum, below the angle of Lewis at the second intercostal space. In adults, the sternum provides ample material for aspiration but is only 1 cm thick and cannot be used for core biopsy. It is possible for the physician to accidentally transfix the sternum and enter the pericardium within, damaging the heart or great vessels.

• Anterior medial surface of the tibia in children younger than age 2. This site may be used only for aspiration.

• Spinous process of the vertebrae, ribs, or other red marrow–containing bones. These locations are available but are rarely used unless they are the site of a suspicious lesion discovered on a radiograph.

Adverse outcomes are seen in fewer than 0.05% of marrow collections. Infections and reactions to anesthetics may occur, but the most common side effect is hemorrhage associated with platelet function disorder or thrombocytopenia.

Less than 24 hours prior to bone marrow collection, the medical laboratory scientist collects venous peripheral blood for a complete blood count and blood film examination using a standard collection procedure. Collection is often done immediately before bone marrow collection. The peripheral blood specimen is seldom collected after bone marrow collection to avoid stress-related white blood cell (WBC) count elevation.

Most institutions purchase or assemble disposable sterile bone marrow specimen collection trays that provide the following:

• Surgical gloves.

• Shaving equipment.

• Antiseptic solution and alcohol pads.

• Drape material.

• Local anesthetic injection, usually 1% lidocaine, not to exceed 20 mL per patient.

• No. 11 scalpel blade for skin incision.

• Disposable Jamshidi biopsy needle (Care Fusion; Figure 16-2) or Westerman-Jensen needle (Becton, Dickinson and Company, Franklin Lakes, N.J.; Figure 16-3). Both provide an obturator, core biopsy tool, and stylet. A Snarecoil biopsy needle also is available (Kendall Company, Mansfield, Mass.). The Snarecoil has a coil mechanism at the needle tip that allows for capture of the bone marrow specimen without needle redirection (Figure 16-4).

• Disposable 14- to 18-gauge aspiration needle with obturator. Alternatively, the University of Illinois aspiration needle may be used for sternal puncture. The University of Illinois needle provides a flange that prevents penetration of the sternum to the pericardium.

• Microscope slides or coverslips washed in 70% ethanol.

• Petri dishes or shallow circular watch glasses.

• Vials or test tubes with closures.

• Wintrobe hematocrit tubes.

• Anticoagulant liquid tripotassium ethylenediaminetetraacetic acid (K₃EDTA).

• Zenker fixative: potassium dichromate, mercuric chloride, sodium sulfate, and glacial acetic acid; B5 fixative: aqueous mercuric chloride and sodium acetate, or 10% neutral formalin. Because Zenker fixative and B5 contain toxic mercury, controlled disposal is required.

• Gauze dressings.

The patient is asked to lie supine, prone, or in the right or left lateral decubitus position (lying on the right or left side). With attention to standard precautions, the skin is shaved if necessary, disinfected, and draped. The skin, dermis, and subcutaneous tissue are infiltrated with a local anesthetic solution, such as 1% or 2% lidocaine or procaine, through a 25-gauge needle, producing a 0.5- to 1.0-cm papule (bubble). The 25-gauge needle is replaced with a 21-gauge needle, which is inserted through the papule to the periosteum (bone surface). With the point of the needle on the periosteum, approximately 2 mL of anesthetic is injected over a dime-sized area as the needle is rotated, after which the anesthesia needle is withdrawn. Next, a 3-mm skin incision is made over the puncture site with a No. 11 scalpel blade to prevent skin coring during insertion of the needle.