Parathyroid cysts are rare clinical entities of the neck and superior mediastinum. These cysts often present a difficult diagnostic challenge. They often present as a solitary thyroid nodule and may be difficult to differentiate clinically. The objectives of this study were to review our 27 cases of parathyroid cyst and to suggest the method of diagnostic approach and treatment for parathyroid cyst.

A retrospective study was performed for a 24-year period (1981~2004), on 27 patients operated of parathyroid cyst.

Most of these patients (22/27) complained asymptomatic anterior neck mass at presentation. Preoperative radiologic examinations included ultrasonography (70.4%), computed tomography (25.9%), and ^99mTc thyroid scan (22.2%). Hypercalcemia was detected in 3 cases with high serum calcium (11.3 mg/dl) and intact PTH (158.1 pg/mL). Fine Needle Aspiration (FNA) was performed in nineteen cases. It revealed crystal clear aspirate in non-functioning cysts and hemorrhagic in functioning cysts. In the analysis of the aspirate, mean N-terminal PTH (n=10) and intact PTH (n=9) were 22.5 pg/mL (9.3~45.0) and 686.5 pg/mL (138.0~1500.0), respectively. Mean size of the cysts was 4.0 cm (1.0~9.2) and the left inferior parathyroid glands were most commonly involved (63.0%). All parathyroid cysts were surgically removed.

Parathyroid cysts need to be differentiated from other cystic lesions in the neck and superior mediastinum. Aspiration of crystal clear fluid is highly suggestive of a parathyroid cyst. The aspirate should be analyzed for PTH levels as these are always elevated in parathyroid cysts, regardless of the function. Nonfunctioning cysts may be treated with aspiration alone or sclerosing agents. Surgical excision is indicated for functioning cysts and recurrent case of nonfunctioning cysts.