PGR and breast cancer: Lacking expression of estrogen receptor, progesterone receptor, and type II human epidermal growth factor receptor, TNBC accounts for ∼10%–20% of all pathological types of breast cancer.2 Compared with other breast cancer types, TNBC patients have significantly higher 5-year recurrence rate, are more prone to tumor metastasis, and have a shorter survival time after metastasis and higher mortality.3 Currently, there is no specific treatment for TNBC; chemotherapy is still the only choice for adjuvant therapy or tumor metastasis, and only 30% of patients respond to chemotherapy.4