Triple-negative breast cancer (TNBC), defined by the lack of tumor cell expression of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor type 2, HER2 [1], accounts for approximately 15% of invasive breast cancers [2–4] and is associated with aggressive tumor biology and poor prognosis. This evidence concerns the gene PGR and invasive breast carcinoma.