ESR1 and breast carcinoma: When we explored ER/PR status of breast cancer in addition to methylation status, early age at menarche was associated with low odds of ER + PR+ breast cancer in the presence of methylated RASSF1A (OR = 0.59; 95% CI = 0.40–0.86) (Additional file 1: Table S1), whereas the corresponding OR among women with unmethylated RASSF1A was 1.64 (95% CI = 0.67–3.99) (multiplicative pinteraction = 0.04) (Additional file 1: Table S1).