In a comparison of patients with and without adenomas, the methylation of p16, MLH1 and MGMT could not predict the presence of adenoma (Ye et al, 2006); in colorectal cancer patients, significant methylation was observed at the surgical margin (⩽10 cm from tumour) and was shown to be influenced by gender and by a polymorphism in the DNMT3B gene (Shen et al, 2005; Kawakami et al, 2006; Zhang et al, 2006; Iacopetta et al, 2007). This evidence concerns the gene MLH1 and adenoma.