Unit 2: Bone marrow and cellular abnormalities
Applied Haematology-I notes · PTU syllabus (BMLS501-18)
On this page
Unit summary
The bone marrow shows how blood is being made. This unit covers bone marrow composition and function, aspiration technique in adults and children, processing and staining of aspirates and trephine biopsies, differential counts and cell ratios, red cell morphological abnormalities, leucocyte shifts, and the LE cell phenomenon.
After this unit you can
- Describe bone marrow composition and indications for examination
- Describe aspiration and trephine biopsy techniques
- Perform a marrow differential count and M:E ratio
- Identify red cell and white cell abnormalities and the LE cell
PTU syllabus topics
- Bone marrow composition and function
- aspiration technique (adults and children)
- processing and staining of aspirated marrow and trephine biopsy specimens
- differential cell counts and cellular ratios
- red cell morphological anomalies
- leucocyte disorders (shift to left/right)
- the L.E. cell phenomenon and its clinical significance
Sample
Liquid marrow
Solid core of bone and marrow
Shows
Cell morphology and differential count
Architecture and cellularity
Stains
Leishman, MGG, Perl's for iron
H&E, reticulin
Common site
Posterior iliac crest
Posterior iliac crest
Topic 1
Bone marrow composition and function
- Red marrow: active haemopoiesis — erythroid, myeloid and megakaryocytic cells with stroma, fat cells and macrophages; yellow marrow: mostly fat. Adult red marrow is in the sternum, ribs, vertebrae, pelvis and proximal long bones.
- Unexplained cytopenias
- Anaemia, leucopenia, thrombocytopenia
- Leukaemia and lymphoma
- Diagnosis and staging
- Myeloma
- Plasma cells
- Pyrexia of unknown origin
- Culture, granulomas
- Storage diseases
- Gaucher cells
- Iron stores
- Perl's stain
Topic 2
Aspiration technique
- 1
Sites — posterior superior iliac spine (preferred), sternum (adults only), anterior tibia (infants under 1–2 years)
- 2
Consent; aseptic preparation; local anaesthesia
- 3
Insert Salah or Klima needle with stylet into the marrow cavity
- 4
Remove stylet; aspirate 0.2–0.5 mL quickly
- 5
Make films immediately from particles
- 6
Trephine biopsy (Jamshidi needle) for a core when the tap is dry
- Dry tap: fibrosis, hypercellular marrow (leukaemia), metastases — biopsy needed.
Topic 3
Processing and staining
Aspirate smears
Squash or spread films of particles; air dry
Leishman or May–Grünwald–Giemsa; Perl's Prussian blue for iron; cytochemistry
Trephine biopsy
Fix (formalin), decalcify (EDTA or formic acid), embed, section
H&E, reticulin (fibrosis), PAS, immunohistochemistry
- Trephine shows cellularity and architecture; aspirate shows cell detail.
Topic 4
Differential counts and cell ratios
- Count 300–500 nucleated cells; report percentages of each series.
- Myeloid : erythroid ratio
- 2 : 1 to 4 : 1
- Blasts
- Less than 5%
- Lymphocytes
- 10–20%
- Plasma cells
- Less than 3%
- Megakaryocytes
- Several per low-power field
- Cellularity
- About 100 minus age (%) — roughly 50% in adults
- M:E ratio rises in myeloid leukaemia and infections; falls in haemolysis and megaloblastic anaemia (erythroid hyperplasia).
Topic 5
Red cell morphological abnormalities
Microcytes and hypochromia
Small, pale cells
Iron deficiency, thalassaemia
Macrocytes
Large cells; oval macrocytes
Megaloblastic anaemia, liver disease
Spherocytes
Small, dense, no central pallor
Hereditary spherocytosis, autoimmune haemolysis
Target cells
Central dot
Thalassaemia, liver disease, HbC
Sickle cells
Crescent shape
Sickle cell disease
Schistocytes (fragments)
Helmet cells
DIC, microangiopathy
Tear-drop cells
Teardrop
Myelofibrosis
Inclusions
Howell–Jolly bodies, basophilic stippling, Pappenheimer bodies
Post-splenectomy, lead poisoning, sideroblastic anaemia
Poikilocytosis and anisocytosis
Variation in shape and size
Many anaemias
Topic 6
Leucocyte disorders: shift to left and right
Meaning
More immature neutrophils (bands, metamyelocytes) in blood
More hypersegmented neutrophils (5 or more lobes)
Causes
Acute bacterial infection, inflammation, leukaemoid reaction
Megaloblastic anaemia (B12, folate deficiency), uraemia
- Toxic granulation, Döhle bodies and vacuoles suggest severe infection.
Topic 7
The LE cell phenomenon
- LE cell: a neutrophil that has engulfed a homogeneous, swollen nucleus (haematoxylin body) coated with antinuclear antibody. Demonstrated by incubating clotted blood, which damages cells and releases nuclei.
- Significance: found in about 70–80% of systemic lupus erythematosus; now replaced by more sensitive ANA (immunofluorescence) and anti-dsDNA tests.
Key terms
- Trephine biopsy
- Core of bone and marrow
- Dry tap
- Failed aspiration
- M:E ratio
- Ratio of myeloid to erythroid precursors
- Schistocyte
- Fragmented red cell
- LE cell
- Neutrophil containing a phagocytosed antibody-coated nucleus
Quick revision
- Marrow composition; indications.
- Aspiration sites and technique; trephine; dry tap.
- Aspirate and trephine processing and stains.
- Differential count; normal values; M:E ratio changes.
- Red cell anomalies; left and right shifts; LE cell and SLE.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.Name the preferred site for marrow aspiration in adults.
- Q2.What is a dry tap?
- Q3.Give the normal M:E ratio.
- Q4.In which condition are target cells seen?
- Q5.What is a shift to the right?
- Q6.What is an LE cell?
Long-answer questions
- Q1.Describe the technique of bone marrow aspiration and trephine biopsy.
- Q2.Describe the processing and examination of bone marrow.
- Q3.Describe red cell morphological abnormalities.
Stuck on this unit?
Message SBS on WhatsApp for help with Applied Haematology-I, or to ask about studying B.Sc MLS at Synetic.