Based on recent suggestions proposed by groups that have been assessing the association of MMTV-like with BC for years [15,39,40], who hypothesized that MMTV-like and APOBEC3-mediated mutagenesis may work together to cause BC oncogenesis, we sought to investigate how APOBEC3A/B and MMTV-like env sequences influence BC susceptibility and clinical presentation. This evidence concerns the gene ERVW-1 and breast cancer.