In summary, our results show that co-occurring KRAS mutations exist in up to 8% of KRAS c.34G>T-positive NSCLC tumours, with KRAS c.35G>T being the most frequent and translating to either G12F or G12C & G12V double mutant, when occurring in cis or trans respectively. This evidence concerns the gene KRAS and non-small cell lung carcinoma.