PA19.1-6 | Tuberculous Lymphadenitis — Pathology & Specimen — Summary & Reflection

REFLECT

A colleague tells you that a FNAC report reads: 'Epithelioid cell granulomas with caseous necrosis. ZN stain for AFB — negative. Culture pending.'

The attending physician asks whether treatment for TB should start immediately or whether you should wait for culture results.

Using what you know about (a) the diagnostic significance of caseating granulomas, (b) AFB sensitivity in lymph node FNAC, and (c) the consequences of an 8-week treatment delay — how would you reason through this clinical decision?

Write 3–4 sentences justifying your position. Then check against the clinical pearl above.

KEY TAKEAWAYS

Tuberculous lymphadenitis at a glance:

• Scrofula = cervical TB lymphadenitis — commonest extrapulmonary TB site in India.
• Driven by Type IV (cell-mediated) hypersensitivity: CD4 Th1 → IFN-γ → macrophage activation → epithelioid histiocytes + Langhans giant cells + caseous necrosis.
• Langhans giant cell: multinucleate, nuclei in horseshoe/peripheral wreath — distinguishes from foreign-body giant cells.
• Gross: matted, cheesy yellow-white centre; cold abscess; collar-stud abscess; sinus tract.
• Micro: confluent caseating epithelioid granulomas; amorphous pink caseous necrosis; ZN reveals slender red AFB on blue background.
• Key differential: Sarcoidosis = non-caseating granuloma (no caseous necrosis) + negative ZN.
• Diagnostic pathway: FNAC → biopsy → GeneXpert + culture.
• Negative ZN stain does not exclude TB in a clinical granuloma picture.