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PA17.1 | Aplastic Anaemia & Bone Marrow Examination — SDL Guide (Part 3)

Bone Marrow Aspiration and Biopsy — Indications

Infographic showing bone marrow aspiration and trephine biopsy from the iliac crest with the main diagnostic, staging, monitoring, storage disorder, and iron-store indications. — **Panel A:** Posterior iliac crest site; bone marrow aspiration needle; bone marrow aspiration (BMA) liquid marrow for cytology; trephine biopsy (BMB) intact marrow core for histology; same sitting and same site.. **Panel B:** Unexplained pancytopenia or isolated cytopenia; suspected acute leukaemia; suspected lymphoma for Ann Arbor staging; suspected multiple myeloma; suspected myelodysplastic syndrome; metastatic carcinoma infiltration.. **Panel C:** Fever of unknown origin with suspected haematological cause; treatment response after chemotherapy or transplant engraftment; storage disorders including Gaucher and Niemann-Pick; iron stores by Prussian blue stain..

Bone marrow examination encompasses two complementary procedures:
1. Bone marrow aspiration (BMA) — withdrawal of liquid marrow for cytology
2. Trephine biopsy (BMB) — core of intact marrow tissue for histology

Both are usually performed at the same sitting from the same site.

Indications for bone marrow examination:
1. Unexplained pancytopenia or isolated unexplained cytopenia (as in aplastic anaemia)
2. Suspected acute leukaemia — classification and cytogenetics
3. Suspected lymphoma — staging (Ann Arbor system) requires marrow examination
4. Suspected multiple myeloma — plasma cell percentage for diagnosis and response
5. Suspected myelodysplastic syndrome
6. Staging of solid tumours — marrow infiltration by metastatic carcinoma (breast, prostate, lung, neuroblastoma)
7. Fever of unknown origin with suspected haematological cause
8. Monitoring treatment response — post-chemotherapy, post-transplant engraftment
9. Suspected storage disorders (Gaucher, Niemann-Pick) — foam cells in marrow
10. Iron deficiency confirmation — Prussian blue stain for iron stores (rarely needed today; serum ferritin is used)

Technique and Sites

Diagram showing adult and infant bone marrow examination sites with the posterior superior iliac crest emphasized as the preferred site and a stepwise posterior iliac crest biopsy technique. — **Panel A:** Posterior superior iliac crest, posterior iliac crest, sacrum, iliac bone, lateral decubitus position, preferred adult site, aspiration + trephine biopsy.. **Panel B:** Anterior superior iliac crest, sternum/manubrium, aspiration only, no trephine biopsy, cardiac tamponade risk warning, infant anteromedial tibia site, infants under 1 year.. **Panel C:** Lateral decubitus positioning, skin preparation, local anaesthesia to skin/subcutaneous tissue/periosteum, Jamshidi needle, rotary motion through cortex, marrow aspirate, trephine core biopsy..

Sites for bone marrow examination:

Site	Procedure possible	Notes
Posterior superior iliac crest	Aspiration + trephine biopsy	Site of choice in adults; safe, abundant marrow, away from vital structures
Anterior superior iliac crest	Aspiration + trephine biopsy	Alternative; used if posterior site inaccessible
Sternum (manubrium)	Aspiration only	NO trephine here (risk of cardiac tamponade); still used in some centres for quick aspirate
Tibia	Aspiration in infants <1 year	Anteromedial tibia

Technique summary (posterior iliac crest):
1. Patient positioned left or right lateral decubitus
2. Site identified, cleaned, local anaesthesia to skin, periosteum, and subcutaneous tissue
3. Jamshidi needle (trephine) advanced with rotary motion through cortex into medullary cavity
4. Aspirate first (~0.5 mL only; more dilutes with blood) → smears prepared immediately
5. Trephine core taken from same site, slightly deeper; minimum 1.5 cm needed for adequacy
6. Core fixed in formalin → decalcified → paraffin sections

Four-panel medical diagram showing bone marrow biopsy techniques, microscopic comparisons, procedural capabilities, and dry tap causes. — **Panel A:** Posterior superior iliac crest anatomy, aspiration needle placement, trephine biopsy needle position, patient positioning, cortical bone, trabecular bone. **Panel B:** Bone marrow aspirate cellular morphology, trephine core biopsy architecture, individual cell detail, spatial organization, cellularity assessment. **Panel C:** Aspirate capabilities (cell morphology, blast count, M:E ratio), trephine capabilities (architecture, fibrosis detection, cellularity), respective limitations. **Panel D:** Normal marrow architecture, myelofibrosis with reticulin fibers, packed marrow with cellular infiltration, dry tap mechanism illustration.

Aspirate vs Trephine — What Each Shows

A four-panel medical education diagram comparing bone marrow aspirate cell morphology, trephine biopsy architecture, dry tap causes, and normal versus aplastic trephine cellularity. — **Panel A:** Bone marrow aspirate showing iliac crest needle aspiration, syringe, smear field, individual cell morphology, blasts, erythroid and myeloid precursors, megakaryocyte morphology, M:E ratio, iron stores, immunophenotyping, cytogenetics, and FISH.. **Panel B:** Trephine biopsy showing marrow core architecture, trabecular bone, fat spaces, haematopoietic islands, cellularity, fat-to-haematopoietic ratio, topographic distribution, fibrosis, granuloma, metastatic deposit, focal lesion, and lymphoma infiltration.. **Panel C:** Dry tap flowchart showing failed aspiration despite correct placement, causes including myelofibrosis, packed marrow, and technical failure, followed by mandatory trephine biopsy.. **Panel D:** Trephine biopsy comparison of normal marrow versus aplastic anaemia, highlighting normal balanced cellularity versus hypocellular fatty marrow with sparse haematopoietic cells..

The two procedures are complementary, not interchangeable:

Bone marrow aspirate:
- Shows individual cell morphology (cytoplasmic detail, nuclear chromatin, granules)
- Used for: blast morphology and count, erythroid/myeloid ratio (M:E ratio), megakaryocyte morphology, iron stores (Perls stain), cytochemistry, immunophenotyping, cytogenetics/FISH
- Limitation: cannot show architecture (how cells are spatially organised)

Trephine biopsy:
- Shows marrow architecture — cellularity, fat-to-haematopoietic ratio, topographic distribution of cell lineages
- Detects: fibrosis (reticulin/silver stain), granulomas, metastatic deposits, focal lesions, lymphoma infiltration
- Estimates overall marrow cellularity — critical for aplastic anaemia diagnosis
- Limitation: individual cell morphology is inferior to aspirate

The 'dry tap':
When no marrow can be aspirated despite correct needle placement, this is a dry tap. Causes:
1. Myelofibrosis — fibrosis prevents aspiration
2. Packed marrow — very dense infiltration (hairy-cell leukaemia, ALL, marrow metastasis)
3. Technical failure

A dry tap mandates a trephine biopsy to determine the cause.

Side-by-side histological comparison of normal bone marrow showing 50% cellularity versus aplastic anemia showing severe hypocellularity with fat replacement. — **Panel A:** Normal bone marrow with hematopoietic islands, developing blood cells, adipose tissue, 50% cellularity annotation, 100× magnification. **Panel B:** Aplastic anemia marrow with fat replacement, sparse residual lymphocytes, absent hematopoietic elements, <10% cellularity annotation, 100× magnification.