Spectrum of Pleural Fluid Cytology in a Tertiary Care Hospital: A Prospective Observational Study

Background: Pleural effusion (PE) is a frequent clinical finding with a wide spectrum of underlying etiologies, including infections, malignancies, and systemic disorders. Cytological examination of pleural fluid remains a valuable first-line diagnostic tool, offering rapid, minimally invasive, and cost-effective results. The adoption of standardized reporting frameworks such as The International System for Reporting Serous Fluid Cytopathology (ISRSFC/TIS) enhances diagnostic clarity and consistency. Methods: This was a prospective observational study conducted at a tertiary care hospital. A total of 155 pleural fluid samples were evaluated using cytological analysis and classified according to the TIS system. Patient demographics, sample adequacy, fluid appearance, predominant cellular patterns, and final cytological diagnoses were recorded and interpreted. Results: Out of 155 samples, mean age of patients was 49.93 years, with male predominance (62.6%). Straw-colored fluid was the most common macroscopic presentation (41.9%). Cytological, chronic inflammation with lymphocyte dominance was observed in 68.4% of cases. Malignant cells were identified in three cases (1.9%). Using the TIS classification, 92.9% of samples were categorized as Category II: Negative for Malignancy (NFM), facilitating standardized reporting system. Conclusion: Cytological examination of pleural fluid remains a valuable initial diagnostic tool for evaluating serous effusions. Incorporating the TIS system enhances diagnostic accuracy and consistency, thereby supporting timely clinical decision-making and improved patient outcomes.