Concurrent Parathyroid Carcinoma and Hyperplasia in Hyperparathyroidism

To the Editor, Parathyroid carcinoma is a rare disease that accounts for less than 1% of all hyperparathyroidism [1]. The incidence of parathyroid carcinoma is extremely low, although the apparent incidence of hyperparathyroidism increased after the introduction of multi-channel autoanalyzers. If increased serum calcium and parathyroid hormone (PTH) levels are sustained postoperatively, metastatic lesions should be suspected [2]. Here, we report a case in which high serum calcium and PTH levels were sustained after resection of a parathyroid carcinoma and a final diagnosis of concurrent parathyroid carcinoma and hyperplasia was made. A 74-year-old woman was referred to our hospital following loss of consciousness. She had a 4-year history of severe back pain and was diagnosed with spinal stenosis. Despite medical treatment, her back pain persisted. At presentation, she was stuporous and her blood pressure was undetectable. Mechanical ventilation was started and vasopressors administered. Laboratory results included a serum calcium of 17.7 mg/dL and PTH of 713.9 pg/mL. Computed tomography (CT) revealed a left thyroid mass. Ultrasonography revealed a left parathyroid mass (Fig. 1A). A sesta technetium-99m methoxyisobutylisonitrile (Tc-sestamibi) scintigram revealed no abnormal uptake (Fig. 2). The patient regained consciousness after intravenous hydration and calcitonin treatment. One month later, she underwent a left parathyroidectomy and hemithyroidectomy. Parathyroid carcinoma with capsular invasion was confirmed histologically (Fig. 3). Given her unstable vital signs intraoperatively, the surgeon could not explore the right thyroid gland accurately. The elevated serum calcium and PTH levels decreased after resecting the left parathyroid carcinoma, but were still elevated compared to normal. To detect