Utility of Fine Needle Aspiration Cytology in Bacille Calmette–Guerin Lymphadenitis: An Institutional Experience

Background: The Bacille Calmette–Guerin (BCG) vaccine is a live attenuated vaccine that is a part of the National Immunization Program in India. It protects infants and children from tubercular meningitis and disseminated tuberculosis. It is usually a safe vaccine but can cause mild and severe adverse reactions including suppurative lymphadenitis as well as osteitis. BCG vaccine-induced regional lymphadenitis can be easily misdiagnosed and can lead to unnecessary therapeutic as well as surgical interventions. Fine needle aspiration cytology (FNAC) in such cases is a minimally invasive procedure for not only making an early and accurate diagnosis but can also have a curative role. Aim: To study the utility of FNAC in BCG lymphadenitis and to create awareness regarding this entity. Materials and methods: This study has been conducted for 3 years (December 2021 to December 2023). We analyzed 16 cases of BCG lymphadenitis diagnosed on FNAC. Their clinical presentation, cytomorphological features, and clinical outcomes were studied. Results: Of all the 16 cases, 10 patients were males and 6 were females. The minimum age for the presentation was 5 months and the maximum was 2 years. The majority had left-sided axillary lymph node enlargement without any constitutional symptoms. FNAC yielded pus aspirates in 80% of cases. Cytological examination showed inflammatory cells (62.5%), reactive lymphoid cells (37.5%), and epithelioid cell granulomas with necrosis (18.7%), along with giant cells in 12.5% of cases. Ziehl–Neelsen staining for acid-fast bacilli was positive in 13 cases. On follow-up, lymphadenitis regressed in most of them within a few months of diagnosis. Conclusion: Bacille Calmette–Guerin lymphadenitis is a benign condition that remits spontaneously within a few weeks without any treatment in most cases. A high index of suspicion, clinical history, and FNAC play an important role in its detection and management.