MEN1 and tumor of parathyroid gland: In sporadic parathyroid tumors bearing MEN1 or CDC73 mutations, the deregulation of DNA methylation mechanism and/or of histone modifications, derived by menin or parafibromin loss, substantially concurs to the tumorigenesis, the same way it happens in inherited forms of MEN1- and HPT-JT-related parathyroid tumors.