ESR1 and breast neoplasm: The results of our study confirmed that BRCA1 promoter methylation was significantly correlated with the increased risk of breast cancer and associated with lymph node metastasis, histological grade 3, ER(-), PR(-), triple-negative phenotype and BRCA1 protein expression, which indicated that BRCA1 promoter methylation may be utilized as an effective biomarker in the management of breast tumors.