Therefore, based on the high frequency of EGFR in the post-transformed cases (almost SCLC) [15,30,36,37], the abnormal Rb expression in the non-NEC (mainly ADC) [32], and the above discussions about the reported transformation cases (Table S2) [15,17,18,22,32,36,38,39], the C-NECs all had a common cellular origin. Here, RB1 is linked to neuroendocrine carcinoma.