KITLG and lung cancer: So far, several serum biomarkers for lung cancer have been identified, including fragments of cytokeratin 19 CYFRA 21–1, carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC-Ag), stem cell factor (SCF), neuron-specific enolase (NSE), progastrin-releasing peptide (ProGRP), epidermal growth factor receptor (EGFR), and vascular endothelial growth factor (VEGF) [1,8].