ERBB2 and breast cancer: There are multiple BC subtypes based on genome sequencing and the presence or absence of molecular markers for estrogen or progesterone receptors and human epidermal growth factor 2 (ERBB2), also known as human epidermal growth factor receptor 2 (HER2), with the majority of BC tumors expressing estrogen receptors and/or progesterone receptor (PR) [5, 6].