Intrathyroidal oncocytic parathyroid adenoma in an adult: A diagnostic challenge - Case report

Intrathyroidal parathyroid adenoma ((IPAs) is a rare localization of parathyroid adenomas, potentially leading to both diagnostic and therapeutic challenges. We report a case of primary hyperparathyroidism revealed by bone and joint pain, with an atypical intrathyroidal location of the oncocytic parathyroid adenoma.

A 72-year-old woman was admitted for evaluation and management of chronic bone and joint pain. Laboratory tests revealed hypercalcemia associated with elevated parathyroid hormone (PTH) levels. Cervical ultrasound showed a 3 cm right lobar nodule classified as EU-TIRADS 3. Technetium-99 m sestamibi (MIBI) scintigraphy demonstrated intense uptake at the same location, raising suspicion of either thyroid or parathyroid origin. The patient underwent a right loboisthmectomy. Definitive histological analysis confirmed a 3 cm intrathyroid parathyroid adenoma. Postoperative evolution was favorable, with normalization of serum calcium and PTH levels.

Despite their rarity, IPAs hold significant clinical importance, as their atypical location within the thyroid parenchyma can lead to failed surgical explorations if not properly considered.

This case illustrates the rarity and diagnostic complexity of ectopic intrathyroidal oncocytic parathyroid adenomas, which can lead to failed surgical explorations. This is highlights the importance of a multimodal diagnostic approach including ultrasound, MIBI scintigraphy, and histopathology for optimal management.