A Case of Primary Hyperparathyroidism due to Intrathyroidal Parathyroid Cyst

Abstract

Parathyroid cysts constitute 0.08–3.41% of all parathyroid masses. Intrathyroidal parathyroid cysts, however, are rare conditions with only a few cases being reported. Most of the parathyroid cysts are found to be nonfunctional and functional cysts are generally thought to be due to cystic degeneration of parathyroid adenomas. A cystic, smooth contoured lesion of 24 × 19 × 16 mm was observed in left thyroid lobe of a 76-year-old woman during ultrasonography which was performed as routine workup for primary hyperparathyroidism. It was defined as a cystic thyroid nodule at first. Tc99m sestamibi scintigraphy was performed to see any parathyroid lesions, but no radioactive uptake was observed. Intact parathormone (iPTH) level was found to be >600 pg/mL in cyst aspiration fluid. Left lobectomy was performed, with a diagnosis of primary hyperparathyroidism due to functional parathyroid cyst. Serum iPTH level was decreased >50% postoperatively and histopathological evaluation was consistent with an encapsulated parathyroid adenoma with a cystic center. Parathyroid cysts are among rare causes of primary hyperparathyroidism. Diagnosis is made by markedly increased iPTH level in cyst fluid and observation of parathyroid epithelium lining the cyst wall.

A Functional Parathyroid Cyst from the Hemorrhagic Degeneration of a Parathyroid Adenoma

“…In addition, ultrasonography does not provide any information about whether these cysts arise from the parathyroid or thyroid glands, which makes identifying the cystic mass as a parathyroid adenoma difficult (5). The intracystic iPTH levels in fine-needle aspirates are useful for determining whether a cyst is a parathyroid cyst, thyroid cyst, or nonfunctional cyst (6)(7)(8). However, before performing fineneedle aspiration, determining whether or not the cyst is related to parathyroid cancer is important because fine-needle aspiration is contraindicated in parathyroid cancer due to the risk of seeding along the needle tract (10).…”

“…Positive findings on 99m technetium ( 99m Tc) sestamibi scans of functional parathyroid cysts are less frequent than for non-cystic parathyroid adenomas (4), and ultrasonography is not effective at distinguishing between cysts with parathyroid origins and those with thyroid origins (5); therefore, identifying cystic parathyroid adenomas is challenging. However, measuring intracystic PTH levels in fine-needle aspirates from cysts is useful for diagnosing functional parathyroid cysts (6)(7)(8).…”

A case report of a ectopic parathyroid adenoma and literature review

“…Other cases can be found in the tracheoesophageal sulcus, posterior esophageal area, inferior thyroid pole, heart, etc. Based on the histopathology, PA can be divided into solid PA and cystic PA. Studies have suggested that functional parathyroid cysts may be the result of parathyroid adenoma cysts [6,7] . Therefore, cystic PAs are also called functional parathyroid cysts.…”

Intrathyroidal parathyroid adenoma mimicking thyroid cancer

“…According to a previous large series, intrathyroidal PAs account for 1% of all PAs [5]. Cystic intrathyroidal PAs are even rarer, with a few cases described in the literature so far [6][7][8]. The rarity of this entity makes the pre-operative diagnosis elusive.…”