PGR and breast cancer: BC can also be subtyped based on 4 immunohistochemistry (IHC) markers (estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) and Ki67 [3–5]) as triple-negative (TN), HER2 + , luminal B1 (LB1), luminal B2 (LB2) and luminal A (LA).