Cytomorphological Patterns of AFB Positive Tubercular Lymphadenitis: A Cross-sectional Study

Abstract

Introduction: Tuberculosis (TB) remains a global threat despite advancements in diagnostic technologies and treatment options. Tubercular lymphadenitis is the most common presentation of Extra Pulmonary Tuberculosis (EPTB) in developing countries, accounting for approximately 30-52% of cases. Fine Needle Aspiration Cytology (FNAC) plays a crucial role in the cost-effective and efficient outpatient diagnosis of tubercular lymphadenitis. Understanding the different cytomorphological patterns and Acid Fast Bacilli (AFB) density in tubercular lymphadenitis aids in early diagnosis, management, and reducing morbidity and mortality. Aim: To analyse the various cytomorphological patterns observed in tubercular lymphadenitis, along with AFB density. Materials and Methods: The present cross-sectional cytomorphological study study was conducted between September and October 2021. Data from September 2020 to August 2021 were collected from the records of Shanthabai Devarao Shivaram (SDS) Tuberculosis Research Centre and Rajiv Gandhi Institute of Chest Diseases, a tertiary care hospital in Bengaluru, Karnataka, India. Out of a total of 128 patients with lymphadenopathy who underwent FNAC, four cases were excluded due to failed aspiration. The remaining 124 cases were available for analysis. Smears that exhibited features suggestive of tuberculosis were selected and categorised based on cytomorphological patterns into the following groups: Pattern-1 (Exudative), Pattern-2 (Epithelioid granuloma without necrosis), Pattern-3 (Epithelioid granuloma with necrosis), and Pattern-4 (Predominantly Necrosis without epithelioid granuloma). Ziehl-Neelsen (ZN) stained AFB positive smears were further categorised into four groups based on mycobacterial load. The categories included scant (1-9 AFB in 100 fields), 1+ (10-99 AFB in 100 fields), 2+ (1-10 AFB per field), and 3+ (>10 AFB per field). Higher numbers indicated greater infectivity. Statistical analysis was performed using the Chi-square test. A probability level of less than 0.05 (p<0.05) was considered statistically significant. Results: Out of the 124 cases studied, 81 (65.32%) were females and 43 (34.68%) were males, with a female preponderance (1.9:1). The overall prevalence of tubercular lymphadenopathy was 89 cases (71.77%), with Pattern 4 (Acellular necrosis without granuloma) being the most common cytomorphological pattern 25 cases (28.09%) followed closely by Pattern-2 (Epithelioid cell granuloma without necrosis) 23 cases (25.84%). AFB positivity was observed in 57 cases (64.04%). Pattern-1 (Exudative pattern) showed 100% AFB positivity (21 out of 21 cases), while Pattern 4 (Predominantly necrosis without epithelioid granuloma) demonstrated 92% AFB positivity (23 out of 25 cases). Conclusion: Understanding the various cytomorphological patterns in tubercular lymphadenitis is crucial for its diagnosis. Additionally, identifying AFB positivity, acid-fast bacilli distribution, and Bacterial Index (BI) in various patterns aids in planning early treatment and ensuring a favourable prognosis. FNAC serves as an easy, inexpensive, and quick procedure that can help avoid unnecessary surgical intervention or biopsy in the diagnosis of tubercular lymphadenitis.

Keywords

• acid fast bacilli
• epithelioid cell granuloma
• fine needle aspiration cytology