HER2 is a member of the epidermal growth factor receptor (EGFR) family of homologous transmembrane receptor tyrosine kinases (RTK) [22,23,24,25] present in 20–30% of breast cancers, having an important role in the progression of the disease, associated with an aggressive disease course and poor survival [22,23,26]. The gene discussed is ERBB2; the disease is breast cancer.