KRAS and lung adenocarcinoma: The most common mutation subtypes in KRAS-mutant lung adenocarcinoma are codon 12 substitution mutations (purine is replaced by pyrimidine or vice versa) G12C (39%) and G12V (18–21%), followed by transition mutations (purine is replaced by purine or pyrimidine is replaced by pyrimidine) G12D (14–18%) and G12A (10–11%).