The efforts in characterizing the potential mutagenic activity of APOBECs have focused primarily on APOBEC mRNA expression levels, but sometimes the reported enrichment of the mutagenesis associated with a particular A3 enzyme (e.g. A3A) does not correlate with mRNA levels in tumours from the TCGA database [4] raising the possibility that expression levels alone do not determine A3 activity [29]. Here, APOBEC3A is linked to neoplasm.