Unexpected Detection of an Intrathymic Parathyroid Adenoma by Tc-99m-MIBI Scintigraphy

Abstract

Although most parathyroid adenomas are located in the neck, approximately 25% of them are found deep in the mediastinum. These ectopic adenomas are one of the major causes for failure of bilateral neck exploration because it is almost impossible to reach deep mediastinal tissues from a standard neck incision unless sternotomy is performed. So, although preoperative localization methods are not routinely recommended for the surgical planning of primary hyperparathyroidism, whenever ectopic parathyroid tissues is suspected, preoperative localization can guide the surgery and prevent surgical failure. In this report, we present a case with the diagnosis of primary hyperparathyroidism in whom preoperative Tc-99m-MIBI double-phase scintigraphy, performed for an ongoing research project, revealed an unexpected hyperfunctioning parathyroid nodule in the mediastinum. Subsequent computed tomography and magnetic resonance imaging confirmed an ectopic mediastinal parathyroid adenoma. The surgical approach was modified so that a median sternotomy as well as bilateral neck exploration was performed. A large intrathymic parathyroid adenoma was identified and excised through the sternotomy. In this case, Tc-99m-MIBI scintigraphy successfully localized an unexpected hyperfunctioning mediastinal parathyroid adenoma and played a key role in the surgical planning for the patient. Although not recommended for routine preoperative evaluation, scintigraphy can be useful in the preoperative localization of ectopic parathyroid adenomas, and it may make it possible for the surgeon to modify the surgical approach in selected cases. (The Endocrinologist 2005;15: 366 -369) Learning Objectives• Explain the rationale for performing Tc-99m-MIBI scintigraphy when planning surgical treatment of primary hyperparathyroidism as exemplified by this patient, who was scanned as part of an ongoing research project. • Recall which phases of the scintigraphic study displayed increased isotope uptake, and point our whether and how the findings altered surgical planning in this instance. • Compare scintigraphy with various imaging methods for routine preoperative use in patients who are to have an initial parathyroidectomy.P rimary hyperparathyroidism is cured in more than 90% of patients using standard bilateral neck exploration without any need for preoperative localization methods. 1 Parathyroid adenomas are the causative factor for hyperparathyroidism in approximately 85% of cases, and although most of the adenomas are known to be located in the neck, it is been reported in some series that approximately 25% of them can be found deep in the mediastinum. 2,3 These ectopic adenomas are one of the major causes of failure for bilateral neck exploration. 4 Although preoperative localization methods are not routinely recommended for the surgical planning of primary hyperparathyroidism, 1 in some cases, when an ectopic parathyroid pathology is suspected, preoperative localization can be very helpful to the surgery and help avoid surgical failure.

Localization of Ectopic Mediastinal Parathyroid Adenomas Using Indigo Carmine Injection for Surgical Management: A Preliminary Report

“…The EPAs have a variable incidence according to many studies ( 3 , 14 , 15 ). Phitayakorn et al ( 16 ), in a series of 231 patients who underwent surgery for hyperparathyroidism, reported that 16% were ectopic lesions, among which 3% were intra-thymic ( 16 ).…”

The value of intraoperative parathyroid hormone assay in the surgery of mediastinal ectopic parathyroid adenoma (A case series)

“…The ectopic parathyroid adenomas have a variable incidence according to many reported studies [4,5]. Phitayakorn and Mc Henry, in a series of 231 patients operated for hyperparathyroidism, had reported 16% of ectopic lesions among which 3% were intra-thymic [6].…”

An Unusual Mass of Posterior Mediastinum: A Case of Retrotracheal Parathyroid Adenoma Presenting With Primary Hyperparathyroidism

“…The incidence of ectopic intrathymic parathyroid adenomas varies according to authors. 3,4 In the Phitayakorn and Mc Henry 5 series of 231 patients operated for hyperparathyroidism, 16% had ectopic lesions; of which, 3% were intrathymic. In fact, the lower parathyroids and the thymus have a common embryological origin from the third branchial pouch before their respective cervical and mediastinal migration.…”