Bone Marrow Smear - How to Interpret

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.

Blood Cell Smear - How to Interpret

 Systemic approach:

Red Cells

1. Agglutination? - Hemolysis

2. Rouleux (Stacking)? - Indicative of Paraproteinemia (MM)

3. Nucleated Red Blood Cells? - Hemolysis/Bone marrow stress

4. Polychromasia (Increase in Reticulocytes) -Hemolysis/Blood loss (Increased Demand)/Response to Treatment (Ironsubs. in Iron Def. Anemia)

5. Quantity/Size - MCV, Anisocytosis?

6. Quality - Poikilocytosis 

7. Red Cell Inclusions - 

a. Howell jolly bodies (un-removed nucleus parts/Hyposplenism); normal in neonates; hemolysis and megalobastic anemia 

b. Basophilic stippling (ribosomal RNA; best seen in Reticulocytes) - Hemoglobinopathy, MDS, Heavy Metal poisoning (Lead)

c. Pappenheimer bodies (Hemosiderin granules) - Postspelenectomy, Iron-overload, Sideroblastic anemia

d. Malaria

White Cells:

1. Quantity: estimate the Count, Differential

2. Quality: check, Nucleus+Cytoplasma - reactive?dysplasia?malignant population?

a. pleomorphic (reactive) vs monomorphic (malignant)

b. size - small/mature (as lymphocyte), medium (as monocyte), large/immature (as promyelocyte), 

c. Nucleus to cytoplasma ratio (N/C) - high, moderate

d. Nucleus - immature/open/uncondensed/see-through chromatin (blasts) - mature/condensed chromatin/opaque (mature cells); cleft(visible groove)/cleaved(divided)/overlapping/indented -nucleus

e. Cytoplasma

 - color: clear, pale grey (monocyte); faint basophilic (lymphocyte), deep basophilic (plasma cells)

- inclusions: granules, vacuoles, auer rods?

f. company? - other cytopenias/dysplasia/rouleaux/leukoerythrombastic/tear drops?

g. Lymphocytes - reactive/atypical (pleomorphic + abundant cytoplasma) vs malignant (monomorphic, high N/C)

h. Neutrophiles:

- toxic neutophilia: left shift, toxic granulation, toxic vacuolation, dohle bodies, WC count < 40

- hypo-/hypergranulation

- segments (normal 3-4 sausage like, joined by narrow bridge): hypersegmented (Medication - Hydroxycaramid, MTX; B12/Folic acid deficiency, Dysplasia, rarely Iron Deficiency), hyposegmented (such as pseudo-pelger-huet - Dysplasia) and Tacrolimus.

Platelets: 

1. Quantity - estimate the count, 

2. Quality - size variation, granulation