Functional parathyroid cyst: a rare cause of malignant hypercalcemia with primary hyperparathyroidism-a case report and review of the literature.

Parathyroid cysts are rare lesions found in the neck and anterior mediastinum. They are often nonfunctional (>90%) and rarely in the functional form. This paper discusses a case of severe hypercalcemia (23 mg/dL) secondary to a rare functional parathyroid cyst.