More recently, a survey of CpG methylation of six chosen tumor-suppressor genes (ATM, BRCA1, BRCA2, MLH1, RAD51C and TP53) in a single MZ twin pair discordant for childhood leukemia and secondary thyroid carcinoma, identified increased BRCA2 methylation [82]. This evidence concerns the gene BRCA2 and thyroid gland carcinoma.