High frequency of promoter hypermethylation of RASSF1A in tumorous and non-tumourous tissue of breast cancer

RASSF1A promoter hypermethylation occurred at a high frequency in breast cancer tumorous and nontumorous tissues; the majority of tumours have a higher level of methylation status when compared with non-tumorous tissues. This supports the notion that RASSF1A methylation is an early and premalignant alteration.