Based on an immunohistochemical study of the expression of oestrogen and progesterone receptors (ER and PR), as well as type 2 epidermal growth factor receptor (HER2/Neu, ERbB2), by breast carcinoma cells, breast cancer can be classified into 4 molecular subtypes that differ in the clinical prognosis and response to pharmacotherapy (Jarman et al., 2020; Fernández et al., 2018; Wessels et al., 2018). Here, PGR is linked to breast cancer.