It has to be noted, however, that lack of correlation of APOBEC3A expression with the deletion genotype may result from (i) very low levels of APOBEC3A expression (in comparison to APOBEC3B) in some tissues and cell subsets, including T- and B-lymphocytes and breast cancer cell lines [55, 64, 71–73], or (ii) high homology between APOBEC3A and APOBEC3B and other APOBEC family members that might lead to the mismapping of RNAseq reads or cross-hybridization of APOBEC3A-specific probes [55, 64]. This evidence concerns the gene APOBEC3B and breast cancer.