CDKN2A and small cell carcinoma: Luminal cancers harbor fibroblast growth factor receptor 3 (FGFR3) mutations and cyclin-dependent kinase inhibitor 2 A (CDKN2 A) losses whereas basal cancers are rich in tumor protein p53 (TP53) mutations and neuroendocrine cancers show concurrent mutations of TP53 and retinoblastoma (RB1) as seen in small cell neuroendocrine carcinomas [10].