Cytopathology of pleural mesotheliomas.

Pleural mesothelioma is a rare and highly malignant tumor that has shown increasing incidence. In approximately 90% of patients the tumor manifests initially as recurrent, unilateral, bloody pleural effusions; in the remaining 10% of patients the tumor is detected by chest radiography. As a result, pleural mesotheliomas can be diagnosed by cytologic examination of pleural effusions or transthoracic fine-needle aspirates; the cytologic manifestations of such an examination are described in detail. Additionally, the handling of cytologic specimens, diagnostic problems, and the value and limitations of immunocytochemical and electron microscopic studies and other ancillary techniques in the cytologic identification of pleural mesotheliomas are discussed.