PGR and breast cancer: Furthermore, 30 clinical studies3, 4, 6, 12, 13, 14, 16, 18, 27, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 with a total of 5058 breast cancer patients met our selection criteria for analyzing the association between BRCA1 promoter methylation and clinicopathological characteristics which included early age (<50 years) at diagnosis, premenopausal status, lymph node metastasis, histological grade 3, estrogen receptor (ER), progesterone receptor (PR), human epidermal receptor 2 (Her2), triple-negative phenotype and the expression of BRCA1 protein.