CDKN2A and thyroid gland papillary carcinoma: For genes previously reported to be methylated in thyroid cancer, such as TSHR (Xing et al., 2003), or in other cancer types, such as RASSF1A, RAR-β2, p16, CDH1, DAPK, and MLH1, the methylation frequency in papillary thyroid cancer ranges from 15 to 33% (Hoque et al., 2005; Guan et al., 2008; Mohammadi-asl et al., 2011).