KRAS and cancer: Previous studies of CRC comparing mutations in the primary tumour and metastases from the same patient have focused on selected mutations in a few or a restricted panel of genes, i.e. mostly known cancer drivers such as KRAS, BRAF and APC. Mutations in the APC and KRAS genes appear early in tumour development and concordance between the primary tumour and metastases is seen in 88–100% of patients for KRAS mutations [7–11].