AICDA and urinary bladder cancer: Mutagenesis in bladder cancer is mediated, in part, by aberrant APOBEC activity7,19, and consistent with this, AID/APOBEC-associated tri-nucleotide mutational signatures 2 and 13 (16.3% and 20.9%, respectively) were abundant across the 35 cfDNA samples subjected to WES (Supplementary Data 5 and Supplementary Fig. 6).