CYTOPATHOLOGY OF PLEURAL EFFUSIONS AFTER RADIOTHERAPY

The cytomorphology of pleural effusions following ionizing radiotherap y (IRT) has not been studied systematically. To determine if IRT produ ces alterations in pleural fluids that affect the cytopathologic inter pretation of these specimens, two reviewers, without clinical informat ion, independently assessed 55 specimens obtained following IRT and 39 control specimens obtained from nonirradiated cancer patients. None o f the 24 cytologic features studied were identified significantly more frequently by both reviewers in the irradiated specimens. Only one fe ature (bizarre cells) was found to occur significantly more frequently in the irradiated specimens (36% versus 15%, P=.03) by either reviewe r (reviewer B). Four other features showed a tendency to occur more fr equently in the irradiated fluids by one or the other reviewer. They i ncluded degenerative changes (27% versus 13%, P=.09 [reviewer A]), smu dgy chromatin (16% versus 5%, P=.09 [reviewer A]), large cytoplasmic v acuoles deforming the nuclei (44% versus 26%, P=.07 [reviewer B]) and cytomegaly (38% versus 23%, P=.12 [reviewer B]). The utility of these five features in identifying irradiated specimens was rigorously retes ted in a second masked review conducted jointly by the two pathologist s. None of these features was found more frequently in the irradiated specimens in the second analysis. The results suggest that IRT does no t consistently produce distinctive cytologic changes in pleural effusi ons and that a history of IRT should not affect the interpretation of these specimens.