A series of bibliographic databases were reviewed, and among 20 studies investigating the levels of tumor markers in pleural fluid, the following sensitivity/specificity values were derived: CEA + CA 125, 0.65/0.98; CEA + CA 15-3, 0.64/0.98; CEA + CA 19-9, 0.58/0.98; CEA + CYFRA 21-1, 0.82/0.92; CA 15-3 + CYFRA 21-1, 0.88/0.94. The gene discussed is CEACAM5; the disease is neoplasm.