ERBB2 and breast carcinoma: It was the basis for the systematic molecular classification of breast cancer initiated by Perou et al.4 Myoepithelial refers to a mammary cell type playing a key role in breast duct secretion.5,6 Overexpression of Her2 (ERBB2) and a group of related genes marks the Her2 + cohort well-known since the 1990s for highly favorable response to the drug trastuzumab (herceptin).