Tumour biopsy is the gold standard for lung cancer diagnosis due to the potential of investigating targeted biomarkers including carcinoembryonic antigen (CEA), fragments of cytokeratin ‐19 (CYFRA21‐1), squamous cell carcinoma antigen (SCC) and neuron‐specific enolase (NSE) (13, 14). The gene discussed is CEACAM5; the disease is lung cancer.