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. This evidence concerns the gene RB1 and parathyroid gland carcinoma.