CDKN2A and esophageal squamous cell carcinoma: In addition, somatic mutations in several genes with critical roles in carcinogenesis (e.g., TP53, CDKN2A, and BRCA2) have been identified in ESCC patients with LOH in regions that include the genes [7–9], indicating that a wide variety of DNA alterations in numerous genes occur in the development of this tumor.