AICDA and cancer: In our samples, the common mutational signature according to the catalogue of somatic mutations in cancer (COSMIC) (http://cancer.sanger.ac.uk/cosmic/signatures) was signature 1, which is the result of an endogenous mutational process initiated by spontaneous deamination of 5-methylcytosine at CpG, while other mutations were classified into various signatures, including those correlated with DNA mismatch repair (signatures 6, 15 and 26), transcription-coupled nucleotide excision repair (signature 7) or associated with AID activity (signature 9) (Supplementary Fig. S3).