PGR and breast cancer: Triple-negative breast cancer (TNBC) (10–20% of breast cancer) is a subtype of breast cancer with high rates of metastasis and recurrence and lacks of expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), which cannot be treated with traditional hormone therapy and Her2-targeted therapy (Li et al., 2018) (Mouh et al., 2016).