Background: As the accumulation of fluid in the pleural cavity is a common finding in patients with cancer, its diagnosis deserves careful consideration. The aim of this study was to compare the diagnostic value of pleural fluid cytology and biopsy to surgical biopsy in patients with suspected malignant pleural effusions.

Materials and Methods: During a cross-sectional study, patients with exudative pleural effusion admitted to the Massih-Daneshvari hospital (Tehran) during an 18-month period were enrolled to determine the diagnostic value of pleural fluid cytology, closed needle biopsy and surgical biopsy in suspicious cases of malignant pleural effusion followed by a six-month final diagnosis.

Results: A total of 318 patients (218 men and 100 women, aged 15-85) with a mean age of 59 years were recruited in this study. The sensitivity and negative predictive value of cytology for diagnosis of malignant pleural effusion were 32.4% and 65.6% for closed needle biopsy 65.9% and 63.2%, and for surgical biopsy 87.8% and 80%, respectively.

Conclusion: A combination of pleural fluid cytology and biopsy has diagnostic value in 80% of cases of malignant pleural effusion and considering its simplicity, availability and low cost, these methods have acceptable diagnostic values compared to surgical biopsy.