CCND1 and parathyroid gland carcinoma: Examples include retinoblastoma (Rb), p53, breast carcinoma susceptibility (BRCA2), and cyclin Dl/parathyroid adenomatosis gene 1 (PRAD1) genes.(28,29) To date there is no definitive evidence for a primary role of these genes in parathyroid carcinoma, although altered expression of these gene products may participate in the process of malignant transformation.