Triple-negative breast cancers (TNBC) are an aggressive breast cancer subtype devoid of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) amplification, and are, therefore, unresponsive to targeted therapies such as trastuzumab and anti-estrogen therapies. Here, PGR is linked to triple-negative breast carcinoma.