Cytology of pleural effusions in rheumatoid arthritis.

Rheumatoid pleural effusions are relatively uncommon. The cytologic examination of such effusions can be diagnostic of the underlying disease; this is of great clinical significance when the rheumatoid condition has not been diagnosed prior to the pleural involvement. The diagnostic cytologic abnormalities include large elongated and multinucleated giant cells and macrophages in a background of granular and necrotic debris. The cytologic characteristics parallel the histologic features of pleural rheumatoid nodules.