Four BC subtypes were identified: triple-negative BC (TNBC; oestrogen receptor [ER]-, progesterone receptor [PgR]-, and HER2-negative; n = 11), HER2-positive (n = 14), luminal A (ER-positive, low-grade, and low proliferative index; n = 16), and luminal B (ER-positive, high-grade, and high proliferative index; n = 29; Table 1). Here, PGR is linked to breast cancer.