Digital droplet polymerase chain reaction (ddPCR) of the primary tumour and second PM samples for this patient (see Figure 2) showed that KRAS and PIK3CA mutations occurred in the primary tumour at a higher fractional abundance than in the second PM (20.8 versus 0.29 for KRAS and 18.0 versus 0.11 for PIK3CA respectively). Here, KRAS is linked to neoplasm.