APOBEC3A and breast cancer: APOBEC3A/B has already been associated with a greater burden of mutational signatures consistent with APOBEC3 activity and with an increase in the risk of several types of cancer, including BC [26,27,28,29,30], suggesting that carriers of the deleted allele had greater APOBEC3A activity, since the deletion generates a more stable mRNA isoform for APOBEC3A [24].