CDKN2A and adenocarcinoma: In adenocarcinoma and squamous cell carcinoma, various important onco-pathways (e.g., mitogen-activated protein kinase and phosphoinositide 3-kinase pathways) [12, 13], oncogenes (e.g., KRAS, EGFR, BRAF), tumor suppressor genes (e.g., TP53, STK11, CDKN2A), and gene rearrangements (e.g., ALK, ROS, and RET) have been found to be important [14–16].