Parathyroid Carcinoma and Persistent Hypercalcemia: A Case Report and Review of Therapeutic Options.

Parathyroid carcinomas are very uncommon, accounting for 0.1% to 5% of all causes of primary hyperparathyroidism. Parathyroid-jaw tumor syndrome, with a mutation in HRPT2 that encodes parafibromin, is the most common genetic association. Unique features include aggressive clinical course and a lack of preoperative definitive diagnostic criteria. The authors report a case of a 33-year-old male with bilateral nephrocalcinosis, a left-sided neck mass, high calcium, very high parathormone level and a history of parathyroid adenectomy. Computed tomography and 99m-technetium methoxyisobutylisonitrile scan revealed a localized tumor in the left inferior parathyroid region. The patient underwent radical surgery, and histopathology revealed characteristic features of parathyroid carcinoma. Preoperative identification with clinical clues is very important to plan a more radical surgical approach, as both radiotherapy and chemotherapy are ineffective. Recurrence is common and mostly occurs within 2-3 years after surgery. Patient's age, histology and tumor DNA aneuploidy are predictors of survival. Hypercalcemia is controlled with calcimimetics, bisphosphonates and denosumab in inoperable cases. Furthermore, biologic therapy with parafibromin and telomerase inhibitors is under development.