Breast cancer can be classified into four subtypes based on the expression of oestrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor-2 (HER2), including luminal A, luminal B, and HER-2-overexpressing, and triple-negative breast cancer (TNBC; Burguin et al., 2021). The gene discussed is PGR; the disease is triple-negative breast carcinoma.