ABSTRACT
The diagnostic strategy employed in evaluating an effusion with a high index of suspicion for malignancy, as with lymphocytic exudates, is based on the yield and avail ability of the procedures involved. Typically, pleural fluid cytology is the first step in the evaluation process. Cytology is positive in 66% of cases, but the yield depends largely on the skill and experience of the cytopathologist. The optimal volume of fluid needed for cytological analysis is no greater than 100 mL. Blind pleural biopsy is positive in 45% of cases; when performed in combination with pleural fluid cytology, the diagnostic yield for the two procedures is increased to 73%. Further repeated biopsies increase the over all yield by only 2-4%. Flow cytometry for aneuploidy and immunohistochemical staining for tumor markers may define tumor origin or assist in the diagnosis of indis tinct cells. In the remaining undiagnosed patients, medical thoracoscopy is diagnostic in 96% of cases. The negative predictive value of thoracoscopy for malignant pleural disease is 93%.
