RASSF1 and medullary thyroid gland carcinoma: The role of epigenetics in MTC is largely defined as hypermethylation of CpG islands in the promoter region of Ras-association domain family member 1A (RASSF1A)[73,74] and telomerase reverse transcriptase (TERT) genes[75], overexpression of histone methyltransferases like EZH2 and SMYD3[76,77], and microRNAs (miRNAs) expression profile (Fig. 4)[78-84].