In line with this mutational profile, both stable myeloma precursor cases with high APOBEC3A:3B ratio had a translocation between IGH and MAFB reinforcing the notion that APOBEC activity must be assessed in the light of the APOBEC3A:3B ratio, as this appears to highlight different biological and clinical disease entities. This evidence concerns the gene APOBEC3A and plasma cell myeloma.