Alterations in KRAS (Kirsten rat sarcoma viral oncogene homolog), NRAS (neuroblastoma rat sarcoma viral oncogene homolog) and HRAS (Harvey rat sarcoma viral oncogene homolog), the most frequent being the KRAS mutation, which has been described in up to 30% of patients with non-small cell lung cancer predominantly in the adenocarcinoma variant and in smokers [109]. Here, KRAS is linked to adenocarcinoma.