BRCA1 and breast cancer: Meanwhile, studies on mammary cancer evaluating the methylation pattern of single genes did not find any evidence of methylation affecting gene expression regulation, as described for BRCA1 (Qiu and Lind, 2016; Ferreira et al., 2019), ESR1 (Brandão et al., 2018) and P15/CDKN2B (Faro et al., 2018).