LCNEC shares several clinical characteristics and genomic features with SCLC [8], and, similarly to cases of adenocarcinoma transforming to SCLC [9], the underlying mechanism leading to neuroendocrine differentiation may be the inactivation of retinoblastoma 1 (RB1) and tumor protein 53 (TP53). Here, RB1 is linked to large cell neuroendocrine carcinoma.