A definitive diagnosis of malignancy can be made by examination of the pleural tissue. Metastatic malignancy, mesothelioma, lymphoma and leukemia fall into this category. Pleural fluid smears are rarely positive and the yield on fluid culture is very low and time consuming. In the appropriate clinical setting, the demonstration of non-caseating granuloma with negative pleural tissue culture can be considered as acceptable evidence for the diagnosis of sarcoidosis. However, the immunofluorescent stain is diagnostic for lupus.
Drug induced lupus has the same characteristics.
The following lists criteria for selecting a patient with pleural effusion for biopsy. A pleural biopsy will be indicated only in patients with lupus and when another malignancy exists. The main working diagnosis is malignancy in this clinical setting. Most important, I do not want to miss the opportunity to diagnose a granulomatous pleuritis secondary tuberculosis. With increased sophistication, pathologists are able to make a definitive diagnosis of malignancy by pleural fluid cytology.