The studied series consisted of formalin-fixed-paraffin-embedded tissue samples from 70 patients diagnosed with NELT (2000-2006) including tumors of low malignancy potential (3 tumorlets, 33 typical carcinoids), intermediate malignancy potential (3 atypical carcinoids) and tumors of high malignancy potential (10 large cell neuroendocrine carcinomas-LCNEC and 21 small cell carcinoma-SCLC).