ERBB2 and breast cancer: Cancers derived from luminal cells are the most common types of breast cancer expressing hormone receptors for estrogen receptor (ER), progesterone receptor (PR), or the amplified human epidermal growth factor receptor (EGFR) 2/erythroblastic leukemia viral oncogene homolog 2 receptor (HER2/ErbB2/ERBB2)[30].