BRCA1 and breast cancer: The pooled analysis data revealed a significant correlation between BRCA1 gene hypermethylation and advanced breast cancer disease stage, (OR = 0.75: 95% CI: 0.58–0.97; p = 0.03, fixed effects model, Figure 2b), lymph nodes involvement (OR = 1.22: 95% CI: 1.01–1.48; p = 0.04, fixed effects model, Figure 2d), and pre-menopausal status (OR = 1.34: 95% CI: 1.08–1.66; p = 0.008, fixed effects model, Figure 2f).