NSE distribution in patients with different lung tumors in 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; LCNEC, large cell neuro-endocrine carcinoma; AC, atypical carcinoid; TC, typical carcinoid; NSE, neuron-specific enolase.