Removing an Ectopic Cystic Parathyroid Adenoma in the Anterior Mediastinum via Robotic-Assisted Thoracoscopic Surgery

This video demonstrates a case of a seventy-four-year-old woman found to have persistent primary hyperparathyroidism after bilateral neck exploration, implicating an anterior mediastinal cyst as an ectopic parathyroid adenoma. The patient underwent anterior mediastinal mass resection via a left-sided robot-assisted thoracoscopic approach that resulted in normalization of her hypercalcemia. 

The Surgery

First, a 12 mm port was placed in the lateral eighth interspace, an 8 mm port in the axilla, and an 8 mm port in the third rib space laterally. Mediastinal inspection revealed a cystic structure inferior to the innominate vein. The mediastinal pleura was dissected below the sternum from the innominate vein down to the midportion of the diaphragm. Thymic tissue was then separated from the pericardium along the arch of the aorta and the underside of the innominate vein, allowing cyst mobilization toward the right pleural space. Next, thymic material was resected with a good inferior margin to eliminate residual parathyroid tissue. Mobilization of the inferior portion of the cyst was continued from the pericardial and sternal underside, revealing the right pleural space where entry was avoided. The back of the cyst was dissected from the right pleural surface, and the residual pericardium on the right side of the heart was removed, resulting in full mobilization of the cyst. 

Lastly, residual thymic tissue was dissected to ensure good lateral margins. Hemostasis was confirmed, and a 19 French Blake drain was passed into the pleural space. The patient’s postoperative course was uneventful, she was discharged on post-operative day number one, and she remained normocalcemic three months after the surgery. Final pathology revealed an ectopic cystic parathyroid adenoma.

Discussion 

Hypercalcemia is a common laboratory finding on hospital admissions with a broad differential diagnosis (1,2). Treatment of hypercalcemia varies depending on the level of calcium (e.g. mild vs. severe) and can include conservative management, hospital admission with aggressive IV fluids, or surgical interventions, with the fundamental principle being to correct the underlying cause (3). 

Primary hyperparathyroidism (PHPT) is the main culprit of hypercalcemia that can produce elevated or inappropriately normal PTH levels. Furthermore, parathyroid adenoma is the major cause of PHPT, with elevated secretion of PTH from a single gland. However, multiple glands can be involved. Surgery can provide excellent cure rates in the case of parathyroid adenomas, but surgery may not always cure PHPT, leading to persistent PHPT in up to 5 percent of patients (4). Persistent PHPT can be caused by single adenomas, multiglandular disease, parathyroid carcinoma, and multiple endocrine neoplasia. The major etiology of persistent PHPT is the inability to locate the abnormal eutopic or ectopic gland, which is often in a cervical or mediastinal location (5). The abnormal location is a direct consequence of the embryologic development of the thymus, thyroid, and parathyroid glands (6).

Imaging can offer useful spatial location information for surgical approaches of ectopic parathyroid adenomas. Several modalities allow location of ectopic glands, including cervical ultrasonography, Technetium sestamibi scans, 4D CT imaging, MRI, venous sampling, and recent studies have used PET (7,8). However, bilateral neck exploration has remained the gold standard for identifying parathyroid adenomas, with minimally invasive parathyroidectomy (MIP) becoming more common (9). 

This case illustrates that ectopic parathyroid adenoma should remain high on the differential as an etiology of persistent PHPT and that robotic approaches can offer technical and clinical benefits such as improved visualization, decreased postoperative pain, and fast recovery time for curing patients with such etiologies (10).

References

1. Dent DM, Miller JL, Klaff L, Barron J. The incidence and causes of hypercalcaemia. Postgrad Med J. Sep 1987;63(743):745-50. doi:10.1136/pgmj.63.743.745
2. Turner JJO. Hypercalcaemia - presentation and management. Clin Med (Lond). Jun 2017;17(3):270-273. doi:10.7861/clinmedicine.17-3-270
3. Minisola S, Pepe J, Piemonte S, Cipriani C. The diagnosis and management of hypercalcaemia. BMJ. Jun 2 2015;350:h2723. doi:10.1136/bmj.h2723
4. Walker MD, Silverberg SJ. Primary hyperparathyroidism. Nat Rev Endocrinol. Feb 2018;14(2):115-125. doi:10.1038/nrendo.2017.104
5. Nawrot I, Chudzinski W, Ciacka T, Barczynski M, Szmidt J. Reoperations for persistent or recurrent primary hyperparathyroidism: results of a retrospective cohort study at a tertiary referral center. Med Sci Monit. Sep 9 2014;20:1604-12. doi:10.12659/MSM.890983
6. Policeni BA, Smoker WR, Reede DL. Anatomy and embryology of the thyroid and parathyroid glands. Semin Ultrasound CT MR. Apr 2012;33(2):104-14. doi:10.1053/j.sult.2011.12.005
7. Kluijfhout WP, Vorselaars WM, van den Berk SA, et al. Fluorine-18 fluorocholine PET-CT localizes hyperparathyroidism in patients with inconclusive conventional imaging: a multicenter study from the Netherlands. Nucl Med Commun. Dec 2016;37(12):1246-1252. doi:10.1097/MNM.0000000000000595
8. Mohebati A, Shaha AR. Imaging techniques in parathyroid surgery for primary hyperparathyroidism. Am J Otolaryngol. Jul-Aug 2012;33(4):457-68. doi:10.1016/j.amjoto.2011.10.010
9. Wilhelm SM, Wang TS, Ruan DT, et al. The American Association of Endocrine Surgeons Guidelines for Definitive Management of Primary Hyperparathyroidism. JAMA Surg. Oct 1 2016;151(10):959-968. doi:10.1001/jamasurg.2016.2310
10. Ismail M, Maza S, Swierzy M, et al. Resection of ectopic mediastinal parathyroid glands with the da Vinci robotic system. Br J Surg. Mar 2010;97(3):337-43. doi:10.1002/bjs.6905

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