Surgical management of intrathyroidal parathyroid adenoma with nodular goiter: a case report highlighting SPECT/CT...

Intrathyroidal parathyroid adenomas (ITPAs) represent a rare subset of ectopic parathyroid glands, accounting for approximately 1-6% of cases. Their preoperative diagnosis remains a significant clinical challenge, as they are frequently misdiagnosed as thyroid nodules on conventional imaging such as ultrasonography and computed tomography (CT). This diagnostic difficulty is compounded in patients with concurrent thyroid pathology, such as nodular goiter. This case report aims to highlight the critical role of dual-phase technetium-99m-methoxyisobutylisonitrile (^99mTc-MIBI) single-photon emission computed tomography/computed tomography (SPECT/CT) in achieving accurate preoperative localization and facilitating successful surgical management in such complex scenarios.

A 69-year-old woman with a history of longstanding bilateral thyroid nodules was referred for evaluation. Laboratory investigations revealed severe primary hyperparathyroidism (PHPT), characterized by significantly elevated parathyroid hormone (PTH; 1,656 ng/L), hypercalcemia (3.04 mmol/L), and hypophosphatemia. Initial ultrasonography and contrast-enhanced CT of the neck, while identifying multiple thyroid nodules, failed to localize any parathyroid lesion in typical or ectopic sites. Subsequent dual-phase ^99mTc-MIBI SPECT/CT was performed, which precisely identified a large (57 mm × 73 mm) cystic-solid lesion with persistent delayed-phase tracer retention within the left thyroid lobe, diagnostic of an ITPA. The patient underwent a total left thyroidectomy and partial right lobectomy. Histopathological examination confirmed the presence of a cystic parathyroid adenoma within the thyroid parenchyma alongside nodular goiter. The procedure resulted in a complete biochemical cure, with rapid normalization of serum PTH and calcium levels postoperatively.

This case underscores the diagnostic limitations of conventional imaging techniques for locating ITPAs, especially when masked by concomitant thyroid disease. It demonstrates that dual-phase ^99mTc-MIBI SPECT/CT is an indispensable, high-yield imaging modality for precise preoperative localization in these challenging cases. The integration of functional SPECT data with anatomical CT details allows for confident differentiation from thyroid nodules and alters surgical strategy, enabling targeted resection and minimizing the risk of failed exploration. We advocate for the expedited use of this hybrid imaging technique in the diagnostic workflow of PHPT when ectopic or intrathyroidal lesions are suspected, ensuring complete resection and biochemical cure while preserving normal parathyroid function.