Should lymph nodes suspected of tuberculosis be biopsied?

Biopsy of Tuberculosis Lymph Nodes: Diagnostic Approach

Lymph nodes suspected of tuberculosis should be biopsied for definitive diagnosis, with excisional biopsy providing the highest diagnostic yield of approximately 80%. 1, 2

Diagnostic Considerations

Clinical Context

• Tuberculosis (TB) lymphadenitis typically presents as:
  • Painless, unilateral (95%) lymphadenopathy
  • Most commonly affects cervical lymph nodes
  • Insidious onset with possible progression to abscess and sinus formation
  • Minimal systemic symptoms 1

Diagnostic Options

Fine Needle Aspiration (FNA)

• Variable diagnostic yield (50-82%)
• Less invasive than excisional biopsy
• Useful as initial screening procedure
• May be particularly valuable in resource-limited settings and immunocompromised patients 1, 2, 3
• Risk: May lead to fistula formation and chronic drainage if not followed by complete excision 1

Excisional Biopsy

• Highest diagnostic sensitivity (~80%)
• Provides sufficient material for:
  • Histopathology (caseating granulomas)
  • Acid-fast bacilli (AFB) staining
  • Mycobacterial culture
  • Molecular testing 1, 2
• Caution: Excisional biopsy of preauricular lymph nodes carries significant risk of facial nerve injury 1

Needle-Core Biopsy

• Good diagnostic yield (85% in HIV-infected patients)
• Well-tolerated under local anesthesia
• Less invasive than complete excision 3

Diagnostic Algorithm

1. Initial Assessment:

   • Tuberculin skin test (TST) - note that results may be variable in TB lymphadenitis
   • Chest radiograph to rule out pulmonary involvement
   • Contrast-enhanced CT if available (shows asymmetric adenopathy with ring-enhancing masses) 1

2. Biopsy Decision:

   • For accessible peripheral lymph nodes: Proceed with biopsy
   • For mediastinal/hilar nodes: Consider EBUS-TBNA (Endobronchial Ultrasound-guided Transbronchial Needle Aspiration) 1

3. Biopsy Method Selection:

   • First-line: Excisional biopsy for peripheral nodes (except preauricular)
   • Alternative: FNA or needle-core biopsy when:
     • Excision poses significant risk
     • Patient is immunocompromised
     • Resources are limited
     • Rapid preliminary diagnosis is needed 1, 2, 3

4. Sample Processing:

   • Send specimens for:
     • Histopathology (caseating granulomas)
     • AFB staining
     • Mycobacterial culture (gold standard)
     • PCR for M. tuberculosis when available 4

Differential Diagnosis Considerations

• In adults, >90% of culture-proven mycobacterial lymphadenitis is due to M. tuberculosis
• In children, only ~10% of mycobacterial cervical lymphadenitis is due to M. tuberculosis (most are non-tuberculous mycobacteria) 1
• Other causes to consider:
  • Non-tuberculous mycobacterial infection
  • Other infections (bacterial, fungal)
  • Malignancy (lymphoma, metastatic disease)
  • Sarcoidosis 2

Special Populations

Children

• Non-tuberculous mycobacteria more common than TB
• Excisional biopsy generally preferred over FNA 1, 5

HIV-infected Patients

• Higher yield of TB diagnosis from lymph node biopsy
• Needle-core biopsy under local anesthesia is well-tolerated and effective 3

TB-Endemic Areas

• In areas where TB is endemic, non-surgical biopsy may be useful for minimizing unnecessary thoracotomy 1
• EBUS-TBNA has shown high diagnostic yield (79-85%) for TB in mediastinal/hilar lymphadenopathy 1

Biopsy remains the cornerstone for definitive diagnosis of TB lymphadenitis, with the method selection based on node location, available resources, and patient factors. The diagnostic yield is optimized when samples are properly processed for both histopathology and mycobacterial culture.