RASSF1 and parathyroid gland adenoma: In addition, genes that are frequently subject to epigenetic inactivation in human cancers, such as Ras association domain-containing protein 1 (RASSF1A) [52] and hypermethylated in cancer 1 protein (HIC1) [53], are also frequently hypermethylated in parathyroid adenomas, but it is unclear which of these aberrantly methylated genes may be important to the pathogenesis of parathyroid tumors.