Specialty area: Endocrine surgery. Introduction: Essential to successful parathyroid surgery is understanding of the possible anatomic variations in parathyroid gland location. In this case-series, we highlight three patients with uniquely located parathyroid glands as noted during primary neck exploration. Methods: This is a case-series that details three different patients' health histories, diagnostic workups, intraoperative findings, and surgical pathology analyses. All three patients were

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... valuated and treated with parathyroidectomy for hyperparathyroidism between May and September of 2020. All data was collected from patient electronic medical records at UIHealth -University of Illinois at Chicago and de-identified in December of 2020. Results: The first case demonstrated an inferiorly descended left superior parathyroid gland in the mediastinum. The second case exhibited bilateral intrathymic inferior parathyroid. The third case demonstrated a parathyroid adenoma intimately associated with the left vagus nerve, deep in the carotid sheath. Conclusion: These three unique cases demonstrate the variations in parathyroid anatomy that may be encountered prior to and during parathyroid surgery. Increased vigilance for parathyroid ectopy amongst endocrine surgeons in the preoperative imaging and intraoperative settings affords an opportunity to maximize success of primary neck exploration.