Several conventional cancer biomarkers have been utilized to differentiate MPE and benign pleural effusion, but still with low diagnostic utility, including carcinoembryonic antigen (CEA), carbohydrate antigens 125(CA125), carbohydrate antigen 19-9 (CA19-9), carbohydrate antigen 15-3 (CA15-3), cytokeratin 19 (CK19), and neuron-specific enolase (NSE)9. This evidence concerns the gene CEACAM5 and cancer.