APOBEC3A and breast cancer: In addition to the sporadic off-target mutations induced by AID in B cells, APOBEC3A and 3B are thought to be responsible for many of the non-clustered/non-kataegic mutations at TpC dinucleotides observed not only in breast cancers but in other tumour types where the kataegic signature is not obviously present (Kuong and Loeb, 2013).