CEACAM5 and lung cancer: High hopes are placed on the identification of early molecular markers of lung cancer (carcinoembryonic antigen (CEA), Cyfra 21-1, CA72-4 for adenocarcinoma; Cyfra 21-1, squamous cell carcinoma antigen (SCC)), CEA for squamous cell and large cell lung cancer; ProGRP, HCE, CEA for small cell lung cancer) [7].