CEACAM5 and Pleural effusion: Additionally, if cytology is negative, tumor biomarkers in pleural effusion such as carcinoembryonic antigen (CEA), cytokeratin 19 fragments (CYFRA 21-1) and carbohydrate antigen 153 (CA153) can be used for the identification of those patients with a high clinical suspicion for malignancy [4–6].