Cytomorphologic Patterns of Tubercular Lymphadenitis and Its Correlation With ZN Stain and CBNAAT: A Six-Year Study in a Tertiary Medical College of North India.

BACKGROUND: India has the world's highest burden of tuberculosis (TB). Tubercular lymphadenitis accounts for approximately 40% of extrapulmonary cases. The incidence, demographic profile, and cytologic spectrum vary in different regions. We analyzed the cytologic spectrum and diagnostic yield of Fine Needle Aspiration Cytology (FNAC), Ziehl-Neelsen (ZN) staining, and Cartridge-Based Nucleic Acid Amplification Test (CBNAAT) in a tertiary medical college of North India.

MATERIALS AND METHODS: A 6-year retrospective study (2018-2023) was performed, where 201 TB cases out of 854 lymph node FNACs were analyzed. Cases were categorized into four patterns: Pattern A (Necrosis with granuloma), Pattern B (Granuloma only), Pattern C (Necrosis only), and Pattern D (Acute suppuration). Findings were correlated with ZN grading and CBNAAT results.

RESULTS: The incidence of tubercular lymphadenitis was 23.5%. 21-30 years was the most common age group involved (37.8%), with a female predilection (69.6%). Cervical nodes were the primary site of involvement (72.1%). Pattern A was the most common (75%). Overall, ZN positivity was 45.3% and CBNAAT was 62.2%. CBNAAT sensitivity was highest in Pattern D (100%) and Pattern B (85%). ZN staining showed the highest sensitivity in Pattern B (60%), though with low bacterial loads (1+). While 38.8% of cases were positive for both ZN and CBNAAT, 23% were detected by CBNAAT alone.

CONCLUSION: FNAC is an effective first-line tool, but morphological patterns may vary. ZN and CBNAAT are complementary; CBNAAT significantly increases sensitivity, particularly in suppurative or paucibacillary cases. A multimodal approach ensures higher diagnostic accuracy and facilitates early initiation of Antitubercular Treatment (ATT).