ProGRP concentrations in patients with clinical suspicion of lung tumors. *, P>0.05; ***, P<0.001. SCLC, small cell lung cancer; LCNEC, large cell neuro-endocrine carcinoma; AC, atypical carcinoid; TC, typical carcinoid; NSCLC, non-small cell lung cancer; BLD, benign lung disease; ProGRP, roles of gastrin-releasing peptide.