Prostatic adenocarcinoma diagnosed by prostate-specific antigen analysis of pleural fluid

Adenocarcinoma of the prostate may result in a malignant pleural effusion. However, most of these cases involve patients with either a known primary prostate cancer or radiographic evidence of pulmonary metastases. Occasionally, the initial diagnosis of prostate cancer is made because of prostate-specific antigen (PSA) staining cells in the pleural fluid. We report a case of adenocarcinoma of the prostate that was suspected only because of an elevated PSA in the pleural fluid in a patient who lacked malignant cytology, a history of prostate cancer, and radiographic evidence of pulmonary disease.