Diagnostic Utility and Risk of Malignancy Stratification Using the World Health Organization (WHO) Reporting System for Lung Cytopathology: A One-Year Institutional Study

Introduction The World Health Organization (WHO) recently introduced a standardized Reporting System for Lung Cytopathology, classifying respiratory cytology into five diagnostic categories with corresponding risk of malignancy (ROM) and management guidelines. This study applies the WHO system to categorize respiratory tract cytology specimens and assess ROM and diagnostic accuracy for each category. Materials and methods This retrospective study, conducted from July 2023 to June 2024, analyzed respiratory cytology specimens, including bronchoalveolar lavage (BAL), bronchial washings (BW), endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA), and fine-needle aspiration cytology (FNAC). Pleural effusions were excluded. Cytologic diagnoses were correlated with histopathology to determine ROM for individual categories. Results A total of 150 respiratory samples were analyzed, comprising BAL/BW (128), EBUS-TBNA (21), and ultrasonography<i> </i>(USG)-guided FNAC (one). Histopathologic correlation was available for 60 cases (40%). Based on the WHO classification, 28 cases (18.7%) were categorized as insufficient/inadequate/non-diagnostic, 109 (72.7%) as benign, four (2.7%) as suspicious for malignancy, and eight (5.3%) as malignant, and one (0.6%) was categorized as atypical. The estimated ROM for each category was 11.1% (non-diagnostic), 32.5% (benign), 66.6% (suspicious for malignancy), and 75% (malignant). The specificity of BAL/BW and EBUS-TBNA was 100%. Sensitivity varied across sample types, with BAL/BW at 31.25% and EBUS-TBNA at 50%, resulting in an overall sensitivity of 36.4% and a diagnostic accuracy of 71.67%. Conclusion The WHO Reporting System for Lung Cytopathology standardizes diagnostic categorization, improving communication, facilitating risk stratification, and enhancing clinical decision-making. Its implementation supports more accurate malignancy risk assessment, improving patient care.