Retrospective Application of WHO Reporting System for Lung Cytopathology with Assessment of Risk of Malignancy

INTRODUCTION The recently introduced World Health Organization (WHO) reporting system for lung cytopathology presents five diagnostic categories with corresponding risk of malignancy (ROM) and management protocols. This study employs the system to categorize our institutional respiratory tract cytology specimens, evaluating ROM and diagnostic accuracy for each category. METHODS In a retrospective analysis (May 2020 to August 2021), following respiratory cytology specimens were classified based on the WHO categories: bronchoalveolar lavage (BAL), bronchial wash/bronchial brushings (BB/BW), endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA), fine needle aspiration cytology (FNAC), sputum, biopsy imprint (BI), and endotracheal wash. Exclusions comprised Pleural effusions and EBUS-TBNA from mediastinal and hilar lymph nodes. Correlation of cytological and histopathological diagnoses was done to assess ROM collectively and individually. RESULTS A total of 1518 respiratory samples (BAL(968), BW/BB(380), EBUS-TBNA(42), FNAC(32), Sputum(80), BI(11) and endotracheal wash(5) of 1410 patients were screened, of which 522 cases (34.3%) had histopathological correlation. One forty-one cases (9.3%) were ‘Insufficient/Inadequate/Non-Diagnostic’(ND), 1221(80.4%) were ‘Benign’ (B), 3(0.2%) were ‘Atypical’ (A), 32(2.1%) were ‘Suspicious for malignancy’ (SM) and 121(8.0%) were ‘Malignant’ (M). The estimated ROM for each category was 49.2% for ND, 13.3% for B, 66.6% for A, 81.5% for SM and 92.7% for M. FNAC and EBUS-TBNA exhibited the highest sensitivity (100%) compared to BW/BB (66.3%). Specificity ranged from 96.8% to 100% across the samples, while diagnostic accuracy varied from 58.8% to 100%. CONCLUSION Application of the WHO reporting system enhances standardized terminology, aiding clinicians in informed decision-making and improving patient care through accurate risk assessment of malignancy.