Endocrine Abstracts

Parathyroid cysts (PCs) are rare lesions usually found during exploration of neck and mediastinal masses. Ten percent of PCs can be functional and release parathyroid hormones causing hypercalcemia. Most PCs are small but lesions greater than 1 cm can exert pressure effects on adjacent structures\. Diagnosis can be challenging as PCs can mimic thyroid masses with no focal tracer uptake during most functional imaging modalities. Fine needle aspiration (FNA) can help if coupled with intracystic parathyroid hormone (PTH) measurement. Functional and large cysts require surgical excision. We report a case of a 61-year-old male with incidental finding of severe hypercalcemia (corrected calcium 3.96 mmol/l) with a raised PTH (125.8 pmol/l; normal range 1.6–6.9 pmol/l) level during routine biochemical investigations. He had a large underlying mediastinal mass causing local compression, with inconclusive imaging for preoperative localisation of a suspected parathyroid adenoma. During surgical exploration (via a midline sternotomy), he was found to have a PC originating from the inferior pole of the right lobe of the thyroid gland. He underwent a right hemithyroidectomy with cystectomy resulting in significant reduction in intraoperative PTH levels. Histology was positive for a benign parathyroid adenoma with evidence of thyroid tissue surrounding the cyst. Postoperatively patient was nomocalcaemc with a PTH level in range and normal thyroid function tests. Surgery was complicated by recurrent laryngeal nerve palsy. In essence PCs although rare, should be considered in the differential diagnosis of neck masses warranting early surgical intervention to restore calcium homeostasis rapidly.