SOX2 and esophageal squamous cell carcinoma: Recurring focal SCNAs in ESCC included amplifications of SOX2 (3q26.33), TERT (5p15.33), FGFR1 (8p11.23), MDM2 (12q14.3), NKX2-1 (14q13.2) and deletion of RB1 (13q14.2).