ERBB2 and breast cancer: According to histological expression of three receptor proteins, estrogen receptor (ERα; ESR1), progesterone receptor (PGR), and human epidermal growth factor receptor 2 (ERBB2; HER2; Neu), BC is divided into Luminal A, Luminal B, HER-2 positive, and triple-negative breast cancer (TNBC) [2].