Evidence for specific factors (such as for example PTEN inactivation) facilitating the development of genomic instability comes also from previous studies by others and us showing a nonrandom accumulation of amplifications of different genomic regions, including HER2 and MYC, in a subset of breast cancers that are considered to show an “amplifier” phenotype [26, 56–59]. This evidence concerns the gene PTEN and breast cancer.