Parathyroid Cyst: Often Mistaken for a Thyroid Cyst

Parathyroid cysts are rare but clinically significant lesions. They can be functional, mistaken for a thyroid cyst, and/or managed nonoperatively on occasion.

We identified seven patients (1 male, 6 females) with the diagnosis of parathyroid cyst from 1998 to 2003.

Altogether, 33% of the patients had functional cysts. Sestamibi scans were performed in three of the seven patients, including two with functional cysts; none showed focal uptake. In toto, six of the seven cysts (86%) were found in an inferior parathyroid gland. All of the cysts had crystal-clear aspirate. C-terminal parathormone (PTH) levels were obtained from the aspirate from five of the seven (71%) patients. The mean level was 269,736 pg/ml (1970–1,268,074 pg/ml). Surgery was performed in three of the seven (43%) patients. All patients who underwent surgery improved postoperatively based on symptoms and serum levels of calcium and PTH. The four patients (57%) who were treated nonoperatively were subjected to aspiration alone; three (75%) of those patients required multiple aspirations.

Most parathyroid cysts are nonfunctional and are rarely symptomatic. They are usually located in an inferior gland. If aspirated, most of the cysts reaccumulate fluid. Operative management is usually straightforward and alleviates symptoms and any biochemical abnormalities caused by the cyst.