PGR and triple-negative breast carcinoma: Triple-negative breast cancers (TNBC), defined as tumors that are negative for estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), nowadays represent the focus of increasing interest at the clinical, biological and epidemiological level [6–8], due to the aggressive behavior of the tumor, poor prognosis and present lack of targeted therapies [9–11].