KRAS and squamous cell carcinoma: Both LUAD and LUSC risk groups have important gene alterations such as CDKN2A and CDKN2B deletions which are associated with NSCLC [93] and promotes KRAS and EGFR mutant tumorigenesis [94,95] while SOX2 oncogene amplification in LUSC which is a common event in squamous cell carcinomas [96,97] and amplification of PSMD4 in LUAD, with oncogenic roles in breast, hepatocellular, colorectal and prostate cancer cells [98,99,100,101].