Endocrine Abstracts

Introduction: Functional parathyroid cysts represent an uncommon cause of primary hyperparathyroidism (PHPT) and an even rarer cause of a cervical mass.

Case report: A 57-year-old woman was referred to our department following emergency treatment of hypercalcaemic crisis (serum calcium 16.4 mg/dl) with i.v. hydration and zoledronic acid. She was found to have multiple vertebral fractures by plain radiographs one month previously. Despite being diagnosed and treated with cinacalcet for PHPT for a year prior to these events and a neck mass was noted, it was considered a cystic thyroid nodule. At presentation she had generalized weakness and left-sided neck discomfort with pressure symptoms. Her corrected serum calcium was 13.1 mg/dl, phosphate 0.9 mg/dl, PTH 330 pg/ml, alkaline phosphatase 260 (ULN 220 U/l), and kidney function was normal. Past history was notable for partial thyroidectomy in the 1970s. On examination, a firm, fixed cervical mass was palpable from the sternal notch to the jaw angle. On ultrasound, the mass was cystic with various septa and measured 9×4×4 cm. Needle aspiration of the cyst evacuated 45 ml of hemorrhagic fluid, with PTH washout levels measuring 570 pg/ml. Within the next 2 weeks, a hematoma formed that resolved uneventfully, but the cyst recurred almost to its original dimensions, again causing local pressure. At surgery, the cyst measured 6.4×4×4 cm and histology was consistent with hemorrhagic cystic necrosis of parathyroid adenoma surrounded by an intact thick (0.2–0.5 cm) fibrous capsule without evidence of local invasion. Postoperatively, serum calcium and phosphate were 8.6 and 3.8 mg/dl respectively. The patient remains normocalcemic on calcium and vitamin D supplementation 9 months after surgery.

Conclusion: This case highlights that a large functional parathyroid cyst can elude diagnosis because of its rarity; however, early identification is crucial for proper patient management.