In this study, we use the amplification of ERBB2/HER2 oncogene in breast precancer as a model system, not only because it is known to drive HER2-amplified breast cancer development and progression, but also it is acquired at the pre-invasive stages such as atypical ductal hyperplasia (ADH) and ductal carcinoma in situ (DCIS) [7]. This evidence concerns the gene ERBB2 and atypical ductal hyperplasia.