Triple-negative breast cancer (TNBC) that do not express estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) represent an aggressive subgroup of breast cancer (Brewster et al., 2014) with poor prognosis and limited treatment options in the clinic (Foulkes et al., 2010). This evidence concerns the gene PGR and breast cancer.