Absence or reduced BRCA1 expression in tumours without BRCA1 mutations appears linked to hypermethylation of the BRCA1 promoter region [19], a condition reported in 9.1–37% of sporadic breast cancers and associated with infiltrating ductal type, high (grade II-III) tumour grade, ER negativity, basal markers expression, younger age at diagnosis, low BRCA1 mRNA expression and marked reduction or loss of BRCA1 protein expression [19-25]. This evidence concerns the gene ESR1 and breast cancer.