The most striking difference was found in the expression levels of neuroendocrine genes: while type I LCNECs and the majority of SCLC tumors (class III + IV) harbored high levels of neuroendocrine genes (CHGA and SYP; Fig. 3c; Supplementary Fig. 12e; Supplementary Data 12), most LCNECs and some SCLC tumors with RB1 alterations in class II exhibited low levels of these genes (Fig. 3c, Supplementary Fig. 12e). This evidence concerns the gene SYP and small cell lung carcinoma.