We confirm that while the mutational footprints of DNA polymerases η and θ are prominent in some cancers, mutable motifs characteristic of the humoral immune response somatic hypermutation machine, AID, is likely to be the most widespread feature of somatic mutational spectra attributed to any enzyme in cancer genomes (Rogozin et al., 2018b, 2019). The gene discussed is AICDA; the disease is cancer.