Tuberculous lymphadenitis: Comparison of cytomorphology, Ziehl-Neelsen staining, and rapid mycobacterial culture at a pediatric superspecialty hospital

Background: To evaluate and compare the role of Ziehl–Neelsen (ZN) staining and mycobacterial culture in diagnosis of tuberculous lymphadenitis. Materials and Methods: A total of 56 fine needle aspirations (FNAs) from patients who were clinically suspected to have tuberculous lymphadenitis were included. Acid-fast Bacilli detection was attempted by ZN staining on smears as well as culture on Middlebrook 7H9 broth. Percentage positivity of both smears and culture was calculated. Results: Of the 56 cases, 46 showed cytomorphological features consistent with tuberculosis (TB). The most common pattern was only necrosis in 37 cases followed by necrotizing granulomas in 13 cases. ZN-stained smears were positive in 40 cases while culture was positive in only 27 cases. The highest smear and culture positivity was noted in cases with only necrosis. In six cases, diagnosis of TB was made on culture alone since smear was negative in these cases. Conclusion: FNA is a reliable technique for early and accurate diagnosis of tuberculous lymphadenitis in many cases. Mycobacterial culture by newer rapid techniques can assist in bacillary detection in smear-negative cases and also allows for drug sensitivity testing. Hence, culture should be resorted to in such cases.