Fig 1: Two-dimensional scatter plot presenting four clusters obtained with mutant K-RAS and its wild-type allele. (A) Analysis of ctDNA extracted from patient’s plasma. (B) Analysis of ctDNA extracted from patient’s brain tumour mass. In both graphs (A,B), the fluorescence of channel 1 (FAM) is plotted against the fluorescence of channel 2 (HEX) for each drop (colour: blue, black, orange, or green). Drops are grouped into the following groups: FAM negative, negative HEX (doubly negative drops—black marking); FAM positive, HEX negative (positive drops for the sample with mutation—blue marking); FAM negative, HEX positive (positive drops for wild-type sample—green marking); FAM positive, HEX positive (doubly positive drops, containing both wild-type and mutated DNA—orange labelling). The ddPCR™ KRAS G12/G13 Screening Kit (Bio-Rad’s catalogue number 1863506) detects seven K-RAS mutations: G12A, G12C, G12D, G12R, G12S, G12V, G13D (blue labelling), without discriminating each one of them.