The prognostic and predictive markers of breast cancers can be categorized as clinical (e.g., tumor size, lymph node status, stage), morphologic (size, grade, etc.), immunohistochemical (e.g., hormone receptors, Ki-67 labeling index), a single gene (HER2 neu), and multi-gene assays (Oncotype DX (Exact Sciences, Madison, USA); Mammaprint (Agendia, Amsterdam, Netherlands); EndoPredict (Myriad Genetics, Salt Lake City, USA); Prosigna (NanoString Technologies, Seattle, USA)). This evidence concerns the gene ERBB2 and breast cancer.