Triple-negative breast cancer (TNBC), which represents 10–20% of all tumors, is defined by the lack of immuno-histochemical staining for the estrogen and progesterone receptors and the cell surface epidermal growth factor receptor HER2. It has the most unfavorable outcome of all breast cancer subtypes due primarily to its propensity for early metastatic recurrence [26, 27]. Here, PGR is linked to breast cancer.