CDKN2A and small cell lung carcinoma: Whole genome sequencing (WGS) revealed an enormous mutational burden and a high number of genetic alterations that characterize each SCLC subtype more or less specifically: ~90% biallelic loss of TP53 and RB1, overexpression/amplification of cyclin D1 (CCD1), inactivation of cyclin dependent kinase inhibitor 2A (CDKN2A) and alteration in several genes involved in cell cycle regulation (CDK4/6), receptor kinase signaling (KIT, FGFR1), transcriptional regulation (CREBBP, MYC), apoptosis (SOX2, BCL2) and neuroendocrine differentiation/Notch signaling (22).