Interestingly, in four of the 25 non-tumour samples, a very low level of new mutations were identified, including one sample with the R248W TP53 mutation (CBR057, mutation ratio of 2.02%), one sample with a different EGFR E19 deletion variant (CBR060, mutation ratio of 0.26%) and two samples with EGFR E20 insertion variants (CBR115 and CBR135, mutation ratios of 0.06% and 0.04%, respectively). Here, TP53 is linked to neoplasm.