Atypical Cystic Parathyroid Adenoma Masquerading as a Thyroid Nodule and Presenting with Severe Hypercalcemia

Abstract

Background: Primary hyperparathyroidism occurs as a result of isolated parathyroid adenoma in 80% to 85% of all cases. Severe hypercalcemia due to cystic atypical parathyroid adenoma is rare entity. Method: We report a rare case of severe hypercalcemia associated with cystic atypical parathyroid adenoma. Result: 27 year old female presented with nausea, vomiting and abdominal pain. A serum calcium level of 15.8 mg/dl with PTH of 413 was noted on admission. She was initially treated with IV hydration and had ultrasound of neck which showed 2.8 cm complex nodule in right thyroid lobe. After appropriate work up, she underwent a surgical resection of parathyroid adenoma found on CT with 3D reconstruction. Pathology showed a mixed picture more consistent with possible atypical adenoma. Conclusion: Parathyroid cyst is known but rare entity, which is usually nonfunctional. However, atypical cystic parathyroid adenoma with severe hypercalcemia is very rarely reported. It may exhibit some pathologic features of carcinoma, but angio-invasion and/or metastases are not present. Severe hypercalcemia with a large, cystic neck mass should prompt thoughts of cystic atypical parathyroid adenoma versus carcinoma. In both cases, long-term follow up would be prudent. Also, our case emphasizes the importance of knowing ultrasonographic features to differentiate parathyroid adenoma appearing as thyroid nodule.