We report the case of an 82-year-old lady who was admitted with hypercalaemic crisis (adjusted Calcium 4.82 mmol/L) and acute kidney injury (creatinine 169 micromol/L). PTH was 295 pmol/L, raising the suspicion of an underlying parathyroid carcinoma. She had no palpable neck mass. Her ALP was 131 IU/L and Vitamin D 73 nmol/L; myeloma screen was negative and chest radiograph showed no pathology. A DEXA scan revealed osteoporosis. The hypercalcaemic crisis was medically managed with intravenous fluids, calcitonin and pamidronate.
Curiously, in 2013 she had also suffered from a hypercalcaemic crisis complicated by acute pancreatitis (Ca 4.69 mmol/L, PTH 180 pmol/L) but had subsequently been lost to follow-up. She had remained clinically well between the two episodes, but had not had any blood tests for calcium levels.
An ultrasound neck identified a 32×21 mm hypoechoic, avascular, cystic lesion which appeared to arise from the right sternoclavicular joint. As the origin was unclear, FNA and MRI neck were performed. FNA was negative for any malignancy. MRI neck demonstrated a well-circumscribed cystic lesion just posterior to the right sternoclavicular joint, which corresponded to a focus of increased activity on the Sestamibi scan.
As the imaging was concordant, a limited approach parathyroidectomy was undertaken. A 3 g nodule was removed and histology revealed parathyroid tissue, composed of sheets of chief cells with a part cystic/papillaroid arrangement, surrounded by a fibrous capsule. Mitoses and atypia were not evident. The appearances were consistent with a cystic parathyroid adenoma. Postoperatively, her calcium was 2.56 mmol/L and PTH 7.9 pmol/L.
This case highlights a rare case of cystic parathyroid adenoma that mimicked parathyroid carcinoma due to very high PTH levels and a suspicious neck mass. Less than 350 cases of cystic parathyroid lesions have been reported in the literature - accounting for just 0.5-1% of parathyroid pathologies.