Functional Parathyroid Cyst: A Rare Cause of Malignant Hypercalcemia with Primary Hyperparathyroidism—A Case Report and Review of the Literature

Abstract

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. The patient was later found to have a hemorrhagic cyst with compression of the right recurrent laryngeal nerve. Preoperative diagnosis of the lesion was parathyroid carcinoma. However, reexploration of the parathyroid mass along with microscopic study confirmed the diagnosis of a parathyroid cyst. Following cystectomy, the patient restored her baseline functional status with preservation of the right recurrent laryngeal nerve. Postoperative followup three years later showed no evidence of cyst recurrence. This paper illustrates the rare presentation of parathyroid functional cysts with severe hypercalcemia and primary hyperparathyroidism. Physicians should be aware of the presence of hemorrhage, inflammation, and compressive symptoms in these cysts which mimic parathyroid carcinoma. These patients should be managed with aggressive medical and surgical intervention.

An Unusual Cystic Lesion, Parathyroid Cyst

“…They are commonly found in the left inferior parathyroid gland region. [3,5,7] In general they are asymptomatic; however, there may be swelling at the neck, dysphagia, odynophagia and hoarseness associated with recurrent laryngeal nerve paralysis due to the site of involvement, size and compression of the adjacent structures. Rarely, cysts located in the mediastinum may cause respiratory system symptoms.…”

Parathyroid cysts: the Latin-American experience

“…The localization is variable between mandible and the mediastinum (3,22). Although parathyroid cysts are usually non-functioning, around 10% may secrete PTH (2) and produce a primary hyperparathyroidism (26)(27)(28). This duality suggests differences in the pathogenesis of both types of cysts.…”

Parathyroid cyst: A rare benign mediastinal cyst

“…These theories have suggested that parathyroid cysts originate from (i) embryologic remnants of the third and fourth branchial cleft; (ii) previously existing microcysts coalescing into one large cyst; (iii) simple retention of parathyroid secretions; (iv) atrophied remnants of the Kürsteiner canals of parathyroid glands of embryonic life; and (v) cystic degeneration of preexisting adenomas. [4] However, none of these theories can adequately explain the pathophysiology of parathyroid cysts on its own, and it is likely that more than one mechanism is responsible for their formation.…”

“…[4] About 20 to 40% of cases present with signs of hyperparathyroidism and are accompanied by hypercalcemia symptoms such as nausea, vomiting, constipation, bone and joint pain, and pathological fractures. [5,6] In non-functioning cysts, due to the pressure on intra-thoracic organs, signs and symptoms such as dyspnea, dysphagia, vocal cord paralysis, or findings of thrombi caused by brachiocephalic vein or jugular vein compression are possible.…”

“…These cysts can be confused with bronchogenic cysts, duplication cysts, and thymic cysts. [4] Parathyroid scintigraphy is valuable in determining the cysts originating from parathyroid gland. Parathyroid hormone (PTH) levels of the fluid inside the cyst being higher than serum levels are also useful for the diagnosis.…”