Parathyroid carcinoma: two new cases--diagnosis, therapy, and treatment

Carcinoma of the parathyroid gland is a disease only rarely encountered in clinical practice. As most of these tumors retain the ability to manufacture active parathyroid hormone, most patients with the disease present with hypercalcemia, many times symptomatic. Since the tumor accounts for only 0.5% to 4.0% of cases of primary hyperparathyroidism, the diagnosis of parathyroid carcinoma may be unsuspected and delayed. The clinical index of suspicion should be elevated if there is a palpable neck mass, an exceptionally high serum calcium level, and/or recurrence of hypercalcemia following surgery. We review two patients with parathyroid carcinoma who presented with hypercalcemia. In both, the diagnosis of malignancy was made only after microscopic examination of the operative specimen. Surgery consisted of wide local excision in both cases; radiation therapy was administered in one. Postoperative disease-free status is now 23 and 37 months. One of the patients had a history of radiation therapy to the larynx 20 years prior to the development of parathyroid carcinoma. Also reviewed in this paper are the clinical and histopathologic criteria for making the diagnosis of parathyroid carcinoma and the therapeutic approaches and prognosis of this unusual tumor.