Systematic Approach:
1. Adequacy - A good smear shows fat, spicules, and cellular material.
2. Cellularity - Compare hematopoietic cells to fat spaces.
Age-related norms: Cellularity ≈ 100 – age (±10%) (e.g., 40-year-old → ~60% cellularity).
- Hypocellular (e.g., aplastic anemia, marrow suppression).
- Hypercellular (e.g., leukemia, myeloproliferative disorders).
3. E:M/ ratio: erythroid precursors : myeloid precursors ≈ 1:2 to 1:4
- E:M ↑Erythroid Hyperplasia: hemolysis, thalassemia
- E:M ↓Myeloid Hyperplasia/Erythroid Hypoplasia: infections, CML, myeloproliferative neoplasms
4. Erythropoesis:
- Maturation steps: Proerythroblasts → basophilic normoblasts → orthochromatic normoblasts.
- Abnormalities:
Dyserythropoiesis: multinuclearity, nuclear budding, irregular chromatin.
Increased erythropoiesis: hemolytic anemias, blood loss.
Decreased erythrpoiesis: aplastic anemia, marrow infiltration.
5. Myelopoiesis/Granulopoiesis:
- Maturation stages: myeloblasts → promyelocytes → myelocytes → metamyelocytes → bands → neutrophils.
- Look for:
Left shift (immature forms) → infections, leukemias.
Dysgranulopoiesis: hypolobation, hypogranularity.
Blasts >20% = acute leukemia (per WHO).
6. Megakaryopoesis: Normally present in small numbers, large cells with multilobed nuclei.
- Look for:
Increased: myeloproliferative neoplasms (e.g., essential thrombocythemia).
Decreased/absent: aplastic anemia, marrow failure.
Dysplastic forms: micromegakaryocytes, separated nuclei → myelodysplastic syndrome (MDS).
7. Other Cells
- Plasma cells: normally <5%. Increased in plasma cell disorders (e.g., multiple myeloma).
- Lymphocytes: scattered, small.
- Histiocytes/macrophages: may be seen with hemophagocytosis.
- Mast cells: few normally, increased in mastocytosis.
8. Special Features
- Blasts: count percentage (critical for leukemia diagnosis).
- Fibrosis: suggested if “dry tap” on aspiration → confirmed by biopsy.
- Infiltration: metastatic tumors, storage diseases (e.g., Gaucher cells).
- Iron stores (on Prussian blue stain)
a. Normal, increased (anemia of chronic disease), decreased (iron deficiency).
b. Ring sideroblasts → sideroblastic anemia, MDS.
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