ERBB2 and breast cancer: HER2+ breast cancer is characterized by the overexpression of the HER2 receptor, encoded in the ERBB2 gene located on Chromosome 17: Amplification of the Chr17q12 locus leads to the overexpression of the receptor that can be identified through immunohistochemical and transcriptomic approaches (Perou et al., 2000; Burstein, 2005).