CEACAM5 and lung adenocarcinoma: However, no biomarker of lung adenocarcinoma is available for use in clinical practice owing to insufficient evidence of their diagnostic specificity, despite numerous tumour-specific proteins or molecules in blood such as carcinoembryonic antigen (CEA), neurone specific enolase (NSE) and CYFRA21-1, having been shown to be potential biomarkers [2,3].