PGR and breast carcinoma: Triple‐negative breast cancer (TNBC) represents 15%–20% of newly diagnosed breast carcinoma and is characterized by low expression of progesterone receptor (PR), oestrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2).1, 2, 3 Patients with TNBC have a relatively poor outcome and cannot be treated with endocrine therapy or therapies targeted to HER2.