Pleural fluid cytology: immunocytochemistry usage patterns and significance of nondefinitive diagnoses

There has been little study of how pleural fluids are interpreted in actual practice, including the use of immunocytochemistry and nondefinitive diagnoses. Pleural fluid reports (n = 1,330) from 1991-1997 and the University of Iowa cancer database were retrospectively reviewed to determine the cytologic diagnosis, requisition form history, patient survival, and use of immunocytochemistry. Nondefinitive diagnoses were made in 11.3% of cases. Immunocytochemistry was used in 2.6% of cases and aided in making a definitive diagnosis in 71.9% of cases. For patients with a clinical suspicion of malignancy, the percentages of patients who had a nondefinitive, benign, and malignant diagnosis and died of disease were 81.6%, 94.0%, and 90.6%, respectively. In conclusion, if patients had a history of malignancy and a clinical suspicion of recurrence, patient survival was dismal, regardless of the cytologic diagnosis. Immunocytochemistry was used sparsely but often aided in making a definitive diagnosis.