Gamma Probe Detection of Ectopic Parathyroid Adenoma

Prevalence of Thymic Parathyroids in Primary Hyperparathyroidism During Radioguided Parathyroidectomy

Background:

Radioguided surgery has been an effective tool for identifying hyperfunctioning parathyroid glands during routine parathyroidectomy for hyperparathyroidism. The purpose of this study was to examine the role of radioguided surgery for the identification of intrathymic parathyroid glands.

Material and Methods:

Between March 2001 and February 2018, 2291 patients underwent parathyroidectomy by 1 surgeon for primary hyperparathyroidism. Of these patients, 158 (7%) were identified to have an ectopic intrathymic parathyroid gland. All patients underwent radioguided parathyroidectomy. Ex vivo radionuclide counts were used to confirm parathyroid excision with specimen radioactivity of >20% of the background level.

Results:

The mean age was 56 ± 1 years with 74% of the patients being female. Preoperatively, 122 patients underwent sestamibi scan, which correctly identified the affected gland 61% of the time. Mean background radionuclide count was 208 ± 7, mean ex vivo radionuclide count was 127 ± 9, with ex vivo counts of removed glands >20% in all patients. All ectopic parathyroid glands were successfully identified using gamma probe. Ex vivo counts found to be significantly higher in patients with adenomas. Patients with parathyroid adenomas also were older in age and had higher preoperative calcium levels. While 10% of patients with primary hyperparathyroidism have hyperplasia, 42% of patients with thymic parathyroids had hyperplasia.

Conclusions:

Radioguided parathyroidectomy is useful in detecting ectopic parathyroid glands in the thymus. Patients with hyperplasia disproportionately have clinically significant thymic parathyroid glands.

Gamma probe-assisted excision of an ectopic parathyroid adenoma located within the thymus: case report and review of the literature

Primary hyperparathyroidism due to parathyroid adenomas may be associated with ectopic parathyroid gland localization in 20-25% of the patients. We report herein the excision of an ectopic parathyroid adenoma which was detected in the thymus gland by gamma probe intraoperatively. A 38-year-old patient presented to our clinic with a history of bilateral nephrolithiasis, chronic hypercalcaemia, and PTH elevation. A combination of Technetium-99 m sestamibi scintigraphy and Computed Tomography scan of the chest and neck revealed an ectopic parathyroid adenoma of 8.5 mm in its greatest dimension. The patient underwent sternotomy and the adenoma was found within the right lobe of the thymus gland with the intraoperative use of gamma probe. PTH detection and frozen biopsy were performed during surgery and confirmed the successful excision of the adenoma, while mild hypocalcaemia was noticed postoperatively. We conclude that accurate preoperative and intraoperative localization of an ectopic parathyroid adenoma is crucial to successful surgery. The use of at least two diagnostic modalities before surgical excision minimizes the risk of re-operation for recurrent hyperparathyroidism, while the intraoperative use of gamma probe offers a significant advantage over conventional techniques by reducing surgical time, morbidity and/or complications associated with surgical exploration.