The lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression by triple negative breast cancer (TNBC) tumors confers distinct clinical characteristics on this type of breast cancer, particularly aggressive clinical behavior, early recurrence and metastasis, as well as a worse prognosis.[1,2]. The gene discussed is PGR; the disease is breast cancer.