Parathyroid carcinoma (PC) is a highly aggressive endocrine tumor, with an annual incidence of less than 1 per million. Over 90% of patients present with excess parathyroid hormone (PTH), representing <1-5% of all patients with primary hyperparathyroidism. PC is associated with mutations in the HRPT2/CDC73 gene and with decreased parafibromin and calcium-sensing receptor (CASR) expression. Negative parafibromin staining together with a CDC73 gene mutation increases the likelihood of malignancy and also predicts the clinical outcome, namely local invasion and/or metastases and mortality. An increased mortality is predicted by either of these abnormality combined with down regulation of the calcium-sensing receptor (CaSR) expression.
