PGR and breast cancer: These include the oestrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), leading to the classification of BC into specific subtypes: the luminal subtype (ER/PR positive); the HER2 positive subtype (with an overexpression of the HER2 receptor); and the triple-negative or basal-like subtype (TNBC), which lacks all these receptors [3].