ProGRP and NSE distribution in patients with different lung tumors in stage I–II, III and IV. (A) ProGRP distribution in different lung tumors patients with stage I–II, III and IV; (B) NSE distribution in different lung tumors patients with stage I–II, III and IV. ***, P<0.001; **, P<0.05; *, P>0.05. NSCLC, non-small cell lung cancer; SCLC, small cell lung cancer; AC, atypical carcinoid; TC, typical carcinoid; ProGRP, roles of gastrin-releasing peptide; NSE, neuron-specific enolase.