Parathyroid carcinoma.

Although parathyroid neoplasms are common and cause primary hyperparathyroidism, parathyroid carcinoma is a rare entity. At times it can be difficult to diagnose. Patients with parathyroid carcinoma usually present with profound symptoms of hyperparathyroidism and highly elevated serum calcium and parathyroid hormone (PTH) levels. At the time of neck exploration, a large, gray-white, locally invasive tumor is commonly encountered. The course of patients with parathyroid carcinoma is variable; unfortunately, more than 50% have persistent or recurrent disease due to regional or distant disease. Surgical resection is the principal treatment for patients with parathyroid carcinoma. The optimal surgical treatment is en bloc tumor resection with ipsilateral thyroid lobectomy when the diagnosis is suspected and until it is proven otherwise. Patients who have persistent or recurrent parathyroid carcinoma should have localizing studies to identify loco-regional or distant tumor sites. Reoperation in patients with localized parathyroid carcinoma is recommended because it relieves symptoms of hypercalcemia, and it normalizes serum calcium and PTH levels in most patients. For patients who have unresectable parathyroid carcinoma, a protocol-based treatment with chemotherapy and external radiotherapy should be considered. Additionally, second-generation bisphosphonates and the NPS R-568 calcimimetic agent may be useful in normalizing the serum calcium and improving symptoms of hypercalcemia. However, they do not treat the tumor and are rarely effective in the long term.