Multiple Functional Parathyroid Cysts

Abstract

A 43-year-old gentleman was diagnosed with primary hyperparathyroidism during treatment for kidney stones. Serum calcium measured 11.28 mg/dL (normal range, 8.8–10.4), with an elevated serum PTH of 155 pg/mL (normal range, 16–65). He underwent preoperative tumor localization studies. Tc scintigraphy did not show any abnormal tracer uptake. Neck ultrasound identified two large, bilateral, cystic structures in relation to the lower lobes of the thyroid (Figure 1, A and B). Analysis of fluid aspirated from these lesions revealed an extremely high level of PTH ( 5000 pg/mL). The patient underwent neck exploration and removal of bilateral tumors located adjacent to the lower lobes of the thyroid gland and weighing 20 and 2.8 g. The upper parathyroid glands were not enlarged. Histological analysis confirmed cystic parathyroid tumors (Figure 1C). The patient achieved remission postoperatively (serum calcium, 9.52 mg/dL; and PTH, 31 ng/mL). Functional cystic parathyroid tumors are uncommon and occur in only 1–2% of cases of hyperparathyroidism (1). Predominantly cystic multigland disease is exceptionally rare and may not be detected preoperatively. Tumors can be mistaken radiologically for thyroid cysts, but aspiration of the cyst fluid can be useful in confirming their origin (2). Thyroid cyst fluid contains high levels of thyroglobulin, whereas lesions of parathyroid origin have extremely elevated concentrations of PTH. Ultrasound also facilitates the aspiration of cysts with real-time image guidance. This may induce remission of hyperparathyroidism, but relapse is common when cyst fluid accumulates. Injection of ethanol or tetracycline into a functional parathyroid cyst may be curative (3). However, most patients require a parathyroidectomy.