Pitfalls of Intraoperative Parathyroid Hormone Monitoring in Achieving Complete Surgical Resection of Ectopic Mediastinal Parathyroid Adenoma: A Case Report and Literature Review

Ectopic mediastinal parathyroid adenoma is rare and is generally managed by surgical resection as a definitive treatment. Intraoperative parathyroid hormone (ioPTH) monitoring is valuable for ensuring the complete removal of a target lesion. However, there is no consensus criteria regarding the utilization of ioPTH for complete resection in patients with ectopic mediastinal parathyroid adenomas. A 65-year-old woman presented with asymptomatic hypercalcemia, and was subsequently diagnosed as having hyperparathyroidism. Radiological imaging displayed a solid mediastinal tumor, suspected to be ectopic mediastinal parathyroid adenoma. Surgical resection was performed together with ioPTH monitoring. Although a transient increase in intact parathyroid hormone (iPTH) level was noted, a 22% decrease in iPTH level compared with the preoperative peak iPTH level was observed 30 minutes after the resection. Intraoperative frozen section diagnosis confirmed complete resection of the ectopic mediastinal parathyroid adenoma. Serum iPTH and calcium levels rapidly decreased postoperatively. The patient was discharged without any complications, and no recurrence was found. We herein report a case of a patient in whom thoracoscopic removal of an ectopic mediastinal parathyroid adenoma using ioPTH monitoring resulted in a successful postoperative outcome. Our present case demonstrates that although ioPTH monitoring is important, it is also crucial to avoid stimulation of the tumor by intraoperative compression and to confirm complete resection by additional modalities, such as by pathological analysis.