WT1 and malignant tumor of parathyroid gland: Promoters of three additional tumor suppressor genes, CDKN2B and CDKN2A, encoding, respectively, the p15INK4b and p16INK4 inhibitor of cyclin kinase, and, thus, negatively controlling cell cycle progression, and the Wilm’s tumor 1 (WT1) gene, encoding a transcription factor that plays an important role in cell growth and differentiation, have been found to be hypermethylated, and totally or partially silenced, in both benign and malignant parathyroid tumors [52].