The TERT promoter mutations (TPMs) are generally mutually exclusive and occur in >50% of bladder cancer, adult glioblastoma, hepatocellular carcinoma (HCC), and melanoma (Horn et al. 2013; Huang et al. 2013; Killela et al. 2013; Vinagre et al. 2013; Borah et al. 2015; Bell et al. 2016), roughly at par with the various TP53 mutations as the most frequently mutated protein-coding gene (Olivier et al. 2010). The gene discussed is TERT; the disease is glioblastoma.