Supernumerary ectopic parathyroid adenoma in the aortopulmonary window: Navigating diagnostic and surgical challenges.

Background: Primary hyperparathyroidism (PHPT) is the most common cause of hypercalcemia and has shifted from a rare condition to a common endocrine disorder. Advances in diagnostic methods have led to more incidental diagnoses, particularly in asymptomatic patients. Ectopic parathyroid adenomas are a rare cause of PHPT, with the vast majority of cases involving parathyroid glands in typical anatomical locations. However, the occurrence of a fifth parathyroid adenoma is exceptionally uncommon, especially when located in an ectopic position.

Methods: We report an uncommon case of primary hyperparathyroidism in a 60-year-old male with longstanding hypercalcemia attributed to a fifth ectopic parathyroid adenoma localized in the aortopulmonary window. Initial imaging modalities failed to localize the adenoma, which was detected by 4D-CT but not on SPECT/CT, and remission was achieved through surgical resection, with intraoperative PTH monitoring confirming total resection.

Conclusions: Delayed diagnosis of ectopic parathyroid adenomas can lead to complications, as in our patient with nephrolithiasis and hypercalcemia. Advanced imaging techniques like 4D-CT are crucial when conventional methods fail. Embryological anomalies can result in ectopic or supernumerary parathyroid glands, complicating localization. Intraoperative PTH monitoring ensures complete resection and lowers reoperation rates. Conclusions: This case highlights the challenges of diagnosing ectopic parathyroid adenomas and the importance of considering rare ectopic adenomas in patients with PHPT, particularly when standard imaging doesn't yield conclusive results. We also discuss the role of advanced imaging modalities and intraoperative PTH monitoring in guiding surgical decisions and determining the appropriate point to conclude the procedure, ensuring successful outcomes.