Several serum biomarkers, such as carcinoembryonic antigen (CEA) 13, cytokeratin 19 fragment (Cyfra21-1) 14, tissue polypeptide antigen (TPA) 15, squamous cell carcinoma antigen (SCC) 16, stem cell factor (SCF) 17, granulocyte-macrophage colony-stimulating factor (GM-CSF) 18, and vascular endothelial growth factor (VEGF) 19 had been identified to be specifically associated with lung cancer. The gene discussed is KITLG; the disease is lung cancer.