Diagnosis relies on the characteristic cytopathology of the exudative pleural fluid, which contains elongated and giant multinucleated macrophages in a sea of amorphous granular material. The absence of mesothelial cells is also characteristic (Champion, 1968). While these findings are highly specific for<unk>  (Nosanchuk et al., 1968; Geisinger, 1985; Engel, 1986; Montes, 1988; Shinto, 1988),<unk>  must be considered if more than one of the above cytologic findings are detected.
Rheumatoid pleuritis
Pleural empyema
Pulmonary sequestration
Tuberculous pericarditis
Lung abscess
Malignant pleural effusion
Cryptogenic organizing pneumonia
Tuberculosis