PGR and breast cancer: Hence, breast cancer types are categorised into the following groups on the basis of their receptor status: (a) oestrogen receptor (ER) or progesterone receptor (PR) positive; (b) human epidermal growth factor receptor 2 positive (amplification of cerbB2) with or without ER and PR positive; and (c) triple-negative breast cancer (TNBC) defined by the absence of ER/PR expression and human epidermal growth factor receptor 2 amplification [2].