RASSF1 and adenoma: ESR1 has been shown to occur in histologically normal colon epithelium in an age dependent fashion [16],[37], CDH13 is also frequently methylated in CRC and seems to be correlated with the adenoma-carcinoma transition, like other genes with methylation frequencies > 30% (CDKN2B, RASSF1, RARB, APC and TIMP3).