CDKN2A and esophageal squamous cell carcinoma: The shared genetic alterations observed in matched ESD and ESCC samples were considered trunk events and allowed for the identification of driver genes underlying the development of ESCC from ESD; three categories of trunk genes were identified, including DNA repair and apoptosis genes (such as TP53 and CDKN2A); proliferation genes and oncogenes; cell adhesion; and junction genes [10].