Mutational signatures in RRMM. (A) A 96-class plot of mutational frequencies in the pyrimidine context, color-coded by nucleotide change and further subdivided on the basis of the 5′ and 3′ nucleotides. (B) De novo extraction of the mutational signatures contributing to the spectrum. (C) Proportion of mutations caused by signature MM1 in people who did not receive (blue) or did receive (yellow) high-dose melphalan before sampling.