Ectopic intrathyroidal nonfunctioning parathyroid cyst

Parathyroid cysts: A review of 359 patients reported in the international literature

BACKGROUND

Parathyroid cysts are lesions that represent 1-5% of neck masses. They are subdivided into two categories: functioning and non-functioning.The aim of the present review is to give a detailed account of all reported cases of parathyroid cysts in the literature and to analyze statistically the available data.

METHODS

A bibliographic research was performed from 1905 until 2016. A database with the patients' characteristics was made and analyzed statistically.

RESULTS

A total of 218 articles were found, reporting 359 cases of cysts. Mean age of patients was 49.24 y/o and the male/female ratio was 1:1.85. The most common locations were left thyroid lobe (113/358 patients, 31.6%), and superior mediastinum (69/358 patients, 19.3%), while the most common symptoms were neck mass (148/355 patients, 41.7%), compressive symptoms (73/355 patients, 206%) and hyperparathyroidism (62/355 patients, 17.5%). Non-functioning cysts were more frequent (220/357 patients, 61.6%). Regarding dimensions, mean diameter was 4.88 cm. Ultrasound and FNA are used for their diagnosis, while cystic fluid analysis may help the differential diagnosis. Recurrences were mentioned in 27/97 patients (27.8%) with available data. No deaths due to parathyroid cysts were mentioned in the literature.

CONCLUSION

Parathyroid cysts should be taken into consideration in case of parathyroid dysfunction or asymptomatic neck mass. The surgeon's careful manipulations on the cyst are crucial for a definitive treatment.

A Case of Primary Hyperparathyroidism due to Intrathyroidal Parathyroid Cyst

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. Tc^99m 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.

Needle aspirate PTH in diagnosis of primary hyperparathyroidism due to intrathyroidal parathyroid cyst

Parathyroid cysts are rare (0.8–3.41% of all parathyroid lesions) and usually arise secondary to cystic degeneration of parathyroid adenomas. Intrathyroidal parathyroid cysts are extremely rare with only three cases reported till date. We present a 24-year-old female with clinical and biochemical features of primary hyperparathyroidism (PHPT; Ca²⁺: 12.1 mg/dl; intact parathyroid hormone (iPTH): 1283 pg/ml) and poor radiotracer uptake with minimal residual uptake in the left thyroid lobe at 2 and 4 h on Tc^99m sestamibi imaging. Neck ultrasonography (USG) revealed 0.6×1 cm parathyroid posterior left lobe of thyroid along with 22×18 mm simple thyroid cyst. USG-guided fine-needle aspiration (FNA) and needle tip iPTH estimation (FNA-iPTH) from parathyroid lesion was inconclusive (114 pg/ml), necessitating FNA of thyroid cyst, which revealed high iPTH (3480 pg/ml) from the aspirate. The patient underwent a left hemithyroidectomy. A >50% drop in serum iPTH 20 min after left hemithyroidectomy (29.4 pg/ml) along with histopathology suggestive of intrathyroidal cystic parathyroid adenoma (cystic lesion lined by chief cell variant parathyroid cells without any nuclear atypia, capsular or vascular invasion surrounded by normal thyroid follicles) confirmed that the parathyroid cyst was responsible for PHPT. This report highlights the importance of FNA-iPTH in localizing and differentiating a functional parathyroid lesion from nonfunctional tissue in PHPT.