KRAS and lung adenocarcinoma: The RAS family of genes is composed of three members with high sequence homology: HRAS, NRAS and KRAS, of which there are two alternative splicing isoforms, KRAS 4A and 4B. In lung adenocarcinoma, KRAS is the predominant RAS gene found mutated (20%), whereas HRAS and NRAS are found mutated in other types of epithelial cancers [17].