Comparative evaluation of bronchial washing cytosmear and cell block for the diagnosis of pulmonary neoplasms

Abstract

Introduction
Lung cancer remains a leading cause of global cancer-related mortality. While bronchial washing via flexible bronchoscopy is a standard diagnostic tool, conventional cytology (CC) often suffers from low sensitivity. This study aimed to evaluate the incremental diagnostic yield and accuracy of combining the cell block (CB) technique with CC in the diagnosis of pulmonary neoplasms.


Materials and methods
In this prospective, observational cross-sectional study (2019–2021), 150 patients with suspected pulmonary neoplasms underwent flexible video-bronchoscopy. Bronchial washings were split for CC (H&E stain) and CB preparation (plasma-thromboplastin method). Diagnostic performance was calculated for CC alone and the combined CC + CB approach, using histopathology as the gold standard. Immunohistochemistry (IHC) for TTF-1 and p40 was performed on CB sections to assess subtyping utility.


Results
Of the 150 patients, 120 were confirmed malignant by biopsy (82 Squamous Cell Carcinoma [SCC], 38 Adenocarcinoma [ADC]). CC alone demonstrated a sensitivity of 55.0%, specificity of 86.7%, and an overall accuracy of 61.3%. The combined CC + CB approach significantly improved diagnostic performance, yielding a sensitivity of 84.2%, specificity of 96.6%, and an accuracy of 86.7%. The combined method identified an additional 35 malignancies missed by CC alone, reducing the false-negative rate from 45.0% to 15.8%. CBs provided sufficient formalin-fixed paraffin-embedded (FFPE) material for definitive IHC subtyping in all tested cases, effectively differentiating ADC (TTF-1+/p40-) from SCC (p40+/TTF-1).


Conclusion
The integration of CB with CC significantly enhances the diagnostic sensitivity and reliability of bronchial washings. The CB technique’s ability to preserve tissue architecture and facilitate ancillary IHC studies supports its routine implementation in clinical protocols to ensure timely and accurate diagnosis of lung malignancies.