Large non-functioning substernal parathyroid cyst: A case report and review of the literature

Parathyroid cysts are rare benign lesions of the head and neck that account for less than 1% of cystic neck masses. We present a rare case of a large 6 cm substernal parathyroid cyst.An otherwise healthy 65 year-old female presented to the otolaryngology clinic for evaluation of an anterior, midline neck mass. On physical exam, she was noted to have a fullness in the anterior neck extending to the sternal notch. CT demonstrated an enlarged thyroid with a cyst extending to the aortic arch. Initial evaluation suggested a bilateral goiter with substernal extension. The cyst was managed with drainage and observation. After two years of continued growth, the patient underwent a left thyroid lobectomy and mediastinal mass resection via the cervical approach. Final pathology was consistent with a parathyroid cyst.Parathyroid cysts are a rare cause of neck mass in an adult, and a 6 cm substernal parathyroid cyst represents an unusual site and size for these cysts. Parathyroid cysts are not often considered on the differential of neck and mediastinal cystic lesions. However, appropriate steps should be taken to ensure a proper diagnosis for any cystic lesion in the neck.