Intrathyroidal Parathyroid Adenoma in Primary Hyperparathyroidism: Are We Overdiagnosing? Case Series and Learning Outcomes

Intrathyroidal parathyroid (IP) adenoma as a cause of primary hyperparathyroidism (PHPT) presents a diagnostic challenge in localization and differentiating it from a thyroid nodule. We report here three distinct cases of PHPT where preoperative imaging findings were compared with surgical and histopathological findings. Case 1 was a typical true IP adenoma, as diagnosed by preoperative sestamibi and ultrasound, and confirmed at surgery and subsequent histopathology. Case 2 was diagnosed by sestamibi and ultrasound as bilateral lower pole IP adenomas which turned out to be thyroid nodules at surgery. Postsurgery, the serum PTH levels dropped only partially and PHPT persisted. Revision surgery was performed, and a right inferior parathyroid adenoma was removed, after which PTH was normalized. Case 3 had a preoperative sestamibi diagnosis of left inferior parathyroid. Preoperative ultrasound suggested a left thyroid nodule/IP along with an associated contralateral right inferior parathyroid nodule. Surgery and subsequent histopathology confirmed left follicular adenoma and right inferior parathyroid adenoma. We discuss the limitations of preoperative imaging modalities in these cases along with their learning outcomes. It is very essential that all the involved clinicians, radiologists, and surgeons are well aware of the diagnostic features and pitfalls associated with IPs so as to enable a correct diagnosis and appropriate surgical or medical management.