CEACAM5 and neoplasm: Other tumor markers in serum and pleural fluid have been reported to be of diagnostic importance such as cytokeratin-19 fragment (CYFRA 21–1), carcinoembryonic antigen (CEA), cancer antigen 15–3 (CA 15–3), cancer antigen 15–9 (CA 15–9) and tissue polypeptide antigen (TPA); however, these markers are not sensitive or specific enough and, thus, cannot be applied clinically [4].