Indeed, in invasive breast cancer, the presence of RARβ methylation in both tumour and serum has been associated with poor disease-free and overall survival [48],[49], while the presence of RASSF1A and APC methylation in pre-operative serum samples predicts for poorer overall survival [50],[51], and APC methylation in breast cancer tissue is associated with reduced time to recurrence [17]. Here, RARB is linked to breast cancer.