A Challenging Case of a Large Ectopic Mediastinal Parathyroid Adenoma

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 199-237-Disorders of Parathyroid Hormone & Calcium Homeostasis
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-231
Maher T. Al-Samkari*1, David L. Steward1, Julian Guitron-Roig2, Dima L. Diab3 and Mercedes Falciglia3
1University of Cincinnati College of Medicine, Cincinnati, OH, 2University of Cincinnati College of Medicine, 3University of Cincinnati College of Medicine, Cincinnati VA Medical Center, Cincinnati, OH
Background: Parathyroid adenomas account for 80% of all causes of primary hyperparathyroidism. A potential cause of initial surgical failure in parathyroidectomy is the presence of unrecognized or asymmetrical parathyroid hyperplasia or ectopic parathyroid tissue.

Clinical case: A 62 year old male with a history of hypercalcemia secondary to primary hyperparathyroidism was referred for medical management.  Despite 2 prior surgical neck explorations with resection of 2 adenomatous (left superior and inferior) parathyroid glands 17 years prior, he had persistent, symptomatic, moderate-to-severe hypercalcemia with fluctuating serum levels as high as 14.8 mg/dL (ref 8.6-10.2 mg/dL) for nearly 1 year. Neck ultrasound prior to referral was unable to visualize any abnormalities beyond multinodular goiter. Sestamibi scan performed at that time raised suspicion for right paratracheal or inferior parathyroid adenoma, however a subsequent third neck exploration which included the upper mediastinum had failed to isolate any new masses. Further management was coordinated with the otolaryngology service.  Ultrasound of the neck by an experienced ultrasonographer again yielded no evidence of an adenoma.  Treatment with calcimimetic (Cinacalcet) was ineffective largely due to symptoms of nausea from the high-doses required. Ultrasound guided inferior internal jugular venous sampling was employed in an effort to lateralize a potential source.  This found symmetric bilateral elevations of PTH of 500 pg/ml (ref 15-70 pg/ml) compared to peripheral levels of 200-300 pg/ml, raising suspicion of an ectopic lesion.  Sestamibi imaging of the neck and chest with CT overlay demonstrated a 2.8 cm soft tissue density in the AP mediastinal window with increased uptake, prompting a consult to thoracic surgery.  After an unsuccessful second mediastinoscopy, median sternotomy confirmed a 2.7 cm ectopic parathyroid adenoma densely adherent to the trachea behind the aortic arch encased in fibrotic tissue. Postoperatively, calcium and PTH levels decreased to 9.7 mg/dL and 80 pg/ml, respectively.

Conclusion: Ultrasonography of the neck by clinicians experienced in localizing parathyroid adenomas is of vital importance in the evaluation of primary hyperparathyroidism.  Up to 1 in 5 parathyroid glands is located ectopically and may be intrathyroidal, undescended, retroesophageal, or mediastinal. Localizing such adenomas may be a particular challenge, requiring an integrative multidisciplinary approach and multiple diagnostic and therapeutic modalities.

Nothing to Disclose: MTA, DLS, JG, DLD, MF

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm