🩸 Bone Marrow Examination: A Comprehensive Guide

A key diagnostic tool for evaluating hematopoiesis and hematologic diseases

Bone Marrow Examination is one of the most essential procedures in hematology.
Because bone marrow is the primary site of blood cell production, direct evaluation of its cellular components provides critical information for diagnosing anemia, leukemia, myeloproliferative disorders, and marrow infiltration.

This guide summarizes the purpose, methods, staining techniques, interpretation, and clinical applications of bone marrow evaluation.

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1. 📌 Clinical Purpose of Bone Marrow Examination

1) Evaluate Hematopoiesis

• Assessment of RBC, WBC, platelet production
• Identification of:
  • Hypocellular marrow (e.g., aplastic anemia)
  • Hypercellular marrow (e.g., MPN)
  • Dysplasia (e.g., MDS)

2) Diagnose Hematologic Malignancies

• Determine blast count in AML/ALL
• Evaluate plasma cell infiltration in multiple myeloma
• Assess marrow involvement in lymphoma

3) Differentiate Causes of Anemia

• Iron deficiency vs. hemolytic vs. megaloblastic
• Assess reticulocyte production and erythroid precursors

4) Identify Infectious or Infiltrative Diseases

• Tuberculosis, fungal infections
• Metastatic cancer to bone marrow

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2. 🧪 Procedure: How Bone Marrow Examination Is Performed

Most samples are obtained from the posterior iliac crest, using two complementary procedures:

1) Bone Marrow Aspiration

Liquid sample → optimal for morphology

• Used for differential count
• Blast evaluation
• Iron stores (Prussian blue)

2) Bone Marrow Core Biopsy (Trephine Biopsy)

Solid core tissue → essential for architecture

• Evaluates cellularity
• Fibrosis
• Tumor infiltration

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3. 🎨 Staining Methods & Microscopic Evaluation

Common Stains

• Wright-Giemsa stain: cell morphology
• Prussian Blue (Iron stain): iron stores, ring sideroblasts
• Reticulin / Trichrome: fibrosis grading
• Immunohistochemistry (IHC): identifying lineage markers (CD3, CD20, MPO, etc.)

Microscopic Evaluation

• Aspiration smear: observed under oil immersion (1000×)
• Core biopsy (H&E): cellularity, fibrosis, architectural patterns

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4. 🔬 Key Findings and Their Clinical Significance

🔴 1) Erythroid Line

• Increased: hemolysis, iron therapy recovery
• Decreased: aplastic anemia
• Dyserythropoiesis: suggests MDS

⚪ 2) Myeloid Line

• Blast >20% → AML/ALL diagnosis
• Toxic granulation → severe infection
• Dysmyelopoiesis → MDS

🟣 3) Megakaryocytes

• Decreased: ITP, aplastic anemia
• Increased: MPN (ET, PMF)
• Dysmegakaryopoiesis: MDS hallmark

🟤 4) Fibrosis

• Reticulin grade elevation → PMF, metastatic tumor, lymphoma
• Severe fibrosis → “Dry tap” on aspiration

🔵 5) Plasma Cells

• >10% suggests multiple myeloma

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5. 🩺 Indications for Bone Marrow Examination

CBC abnormalities

• Unexplained anemia
• Leukocytosis or leukopenia
• Thrombocytopenia

Suspected hematologic malignancy

• Blast flag on CBC
• Multiple myeloma suspicion (CRAB criteria: hyperCalcemia, Renal failure, Anemia, Bone pain)

Infection or infiltration

• TB, fungal infection
• Suspected bone marrow metastasis

Therapeutic monitoring

• Post-chemotherapy marrow recovery
• Minimal residual disease (MRD) in leukemia

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6. 📊 Interpretation: Key Considerations

✔ Combine Aspiration + Biopsy

• Aspiration → detailed morphology
• Biopsy → architecture, fibrosis
  Using only one may cause misinterpretation.

✔ Evaluate for “Dry Tap”

Suggests:

• PMF
• MDS with fibrosis
• Leukemic infiltration

✔ Adjust for Age-Related Cellularity

• Children: normally hypercellular
• Elderly: physiologic hypocellularity

✔ Review Medication History

• Chemotherapy → hypocellularity
• Steroids → lymphopenia

✔ Always correlate with Peripheral Blood Smear

PBS findings often provide diagnostic clues.

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7. 📚 References

• Bain BJ. Bone Marrow Pathology, 5th ed.
• Rodak’s Hematology: Clinical Principles and Applications, 6th ed.
• Henry’s Clinical Diagnosis and Management by Laboratory Methods, 24th ed.
• WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, 5th ed.
• CLSI H21-A5: Bone Marrow Examination Guideline.