ERBB2 and breast carcinoma: Triple-negative breast cancer (TNBC) accounts for approximately 15–20% of all breast carcinomas and is immunohistochemically characterized by the lack of oestrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor (HER2) (also defined by the lack of HER2 amplification by fluorescence in situ hybridization (FISH)).