Genome-wide analyses have identified recurrent copy number alterations in chromosomal regions 11q (harboring CCND1), 3q (SOX2), 2q (NFE2L2), and 9p (CDKN2A), which represent trunk mutations—early clonal events crucial for the initiation and clonal evolution of ESCC (Liu et al., 2017). The gene discussed is SOX2; the disease is esophageal squamous cell carcinoma.