KRAS and neoplasm: EGFR and KRAS mutations were detected by ddPCR. Mutated DNA was found in 85% of stage IV NSCLC patients, with a 70% match between primary tumour and CTCs. In two patients, multiple KRAS mutations were detected. Two patients displayed different mutations compared to the primary tumour, and in two out of four patients with a wild type primary tumour, new mutations were identified: EGFR p.746_750del and KRAS p.G12V.