Ann Thorac Surg 2005;80:1105-1106
© 2005 The Society of Thoracic Surgeons
Case report
Excision of a Mediastinal Parathyroid Adenoma After Coronary Artery Bypass Surgery
Harold L. Lazar, MD
*
,
Elizabeth Oates, MD,
Robert M. Beazley, MD
Department of Cardiothoracic Surgery and the Divisions of Radiology and Surgery, the Boston Medical Center and the Boston University School of Medicine, Boston, Massachusetts, USA
Accepted for publication March 2, 2004.
* Address reprint requests to Dr Lazar, Department of Cardiothoracic Surgery, Boston Medical Center, 88 E Newton St, B404, Boston, MA02118; (Email: harold.lazar{at}bmc.org).
 |
Abstract
|
|---|
In this report we describe the removal of a mediastinal parathyroid adenoma in a patient who had two previous coronary artery bypass graft procedures. The surgical approach and intraoperative localization of the adenoma under these unusual circumstances are reviewed.
|
Introduction
|
|---|
Parathyroid glands may be located in the mediastinum in as many as 25% of patients; however, only 2% cannot be removed through a cervical incision [1]. Median sternotomy, and most recently, video assisted thorascopic surgery (VATS) procedures have been used to remove mediastinal parathyroid lesions [2]. In this report we describe the removal of a mediastinal parathyroid adenoma in a patient who had two previous coronary artery bypass graft (CABG) procedures. The surgical approach and intraoperative localization of the adenoma under these unusual circumstances are reviewed.
A 70-year-old woman presented with an elevated serum calcium level and worsening renal function. In 1986 she underwent a four-vessel CABG procedure and did well until February 1996, when she was readmitted with unstable angina that required intraaortic balloon pump support. After a cardiac catheterization that showed a 90% left main lesion and extensive three-vessel disease with only one patent vein graft, she underwent an emergent six-vessel CABG procedure, including a left internal mammary artery graft to the left anterior descending artery.
In January 2003 she noted increased fatigue, headaches, and had uncontrolled hypertension. An imaging stress test was negative for any electrocardiographic changes or perfusion defects. Her blood urea nitrogen (BUN) and serum creatinine levels, which were normal in the past, were now elevated at 40 mg/dL and 3.9 mg/dL, respectively. Her serum Ca2+ was 12.0 mg/dL and a parathyroid hormone (PTH) assay was 125 pg/mL (normal = 10 to 65 pg/mL). Planar and tomographic parathyroid imaging with technetium 99m (99mTc) tetrofosmin showed a discrete 2.5 cm x 4.0 cm focus of intense tracer localization in the anterior superior mediastinum in close proximity to the sternum that was consistent with a hyperfunctioning parathyroid gland (Fig 1).
View larger version (133K):
[in this window]
[in a new window]
|
Fig 1. Preoperative technetium-99m tetrofosmin planar image shows a single midline focus of abnormal tracer localization in the superior mediastinum.
|
|
On May 23, 2003, she was taken to the operating room for excision of a mediastinal parathyroid gland. To aid with the intraoperative localization of the gland, 99mTc tetrofosmin (20 mCi) was injected intravenously 30 minutes before surgery. An incision was made parallel to the right second costal cartilage, which was excised. Dense adhesions were encountered, and the ascending aorta, innominate vein, and superior vena cava were dissected free from the sternum. The proximity of the innominate vein and ascending aorta to the sternum significantly increased the background counts, so that it was not possible to localize the gland with a hand-held 
scintillation probe. The sternoclavicular junction was divided, a Favaloro retractor was inserted, and the sternal table was gently elevated. A smooth mass adherent to the undersurface of the sternum was now palpable. Sharp dissection was used to totally excise the mass with an intact capsule. The probe was placed directly over the lesion and increased activity was noted. A frozen section confirmed that the mass consisted of parathyroid tissue.
The patient tolerated the procedure well and had an uncomplicated postoperative course. The final pathologic examination of the sections confirmed that the lesion was a parathyroid adenoma. Seven months after the surgery, all her symptoms have resolved. Her serum Ca2+ level is 9.0 mg/dL, PTH is 12 pg/mL, and BUN (17 mg/dL) and serum creatinine (0.9 mg/dL) have returned to normal levels.
|
Comment
|
|---|
Excision of mediastinal parathyroid tumors can be approached either through a median sternotomy or a VATS procedure. However, this patient’s two previous CABG procedures precluded a redo median sternotomy, which would have increased the risks for hemorrhage and damage to existing grafts. Furthermore, the dense adhesions would have made it difficult to identify the lesion with a VATS procedure. Angiographic ablation of this lesion could have avoided surgery; however, this technique has a success rate of only 60%, can result in neurologic complications, and does not provide tissue for autotransplantation if a subtotal parathyroidectomy has already been performed [3]. An anterior approach has been described for removing mediastinal parathyroid tissue and was helpful in this patient [4]. It avoided injury to the ascending aorta and the innominate vein, which were adherent to the sternum, and prevented damage to patent grafts.
Accurate preoperative localization is always important in identifying mediastinal parathyroid glands, but is crucial in a patient with a previous CABG procedure. Almost all ectopic glands are found within or near the thymus gland. However, the thymic fat pad may either be removed or fibrosed as a result of previous CABG procedures, and this makes intraoperative localization difficult. Intraoperative isotopic guidance with a hand-held probe has been used to assist in the localization of mediastinal parathyroid adenomas, but has been successful in only 50% of patients [5]. The readings may vary with the position of the probe and are best obtained if the probe is placed directly against the lesion. In our patient, the close proximity of the aorta and the innominate vein to the tumor falsely elevated the counts. Intraoperative parathyroid hormone assays may be helpful in determining whether multiple adenomas have been removed, but are not helpful in actually localizing the lesion [6].
Technetium-99m tetrofosmin scintigraphy was very helpful in this patient. It not only identified the position of the culprit gland but also localized it in close proximity and just deep to the sternum. Direct visualization of the gland was not possible because it was covered by a rim of fibrous tissue. Division of the sternoclavicular junction and elevation of the sternum was extremely helpful since it allowed for more careful palpation of the lesion. The fibrous tissue over the gland could then be resected, the lesion visualized, and then totally excised with an intact capsule. A median sternotomy would have divided the gland and made complete excision difficult.
Improved radionuclide imaging techniques mean that the discovery of more mediastinal parathyroid adenomas in patients who have had CABG surgery is likely to increase. Understanding the intimate relationship of these glands to the inferior sternal table and the use of the anterior mediastinal approach should greatly facilitate the safe and complete removal of these lesions.
|
References
|
|---|
- Nudelman IL, Deutsch AA, Reiss R. Primary hyperparathyroidism due to mediastinal parathyroid adenoma Int Surg 1987;72:104-108.[Medline]
- Medrano C, Hazelrigg SR, Landreneau RJ, Baley TM, Shawgo T, Grasch A. Thorascopic resection of ectopic parathyroid glands Ann Thorac Surg 2000;69:221-223.[Abstract/Free Full Text]
- Heller HJ, Miller GL, Erdman WA, Snyder WH, Breslau NA. Angiographic ablation of mediastinal parathyroid adenomas, local experience and review of the literature Am J Med 1994;97:529-534.[Medline]
- Schlinkert RT, Whitaker MD, Argueta R. Resection of select mediastinal parathyroid adenomas through an anterior mediasternotomy Mayo Clin Proc 1991;66:1110-1113.[Medline]
- Inabnet WB, Kim CK, Haber RS, et al. Radioguidance is not necessary during parathyroidectomy Arch Aurg 2002;137:967-970.
- Haciyanli M, Lal G, Morita E, Duh QY, Kebeben E, Clark OH. Accuracy of preoperative localization studies and intraoperative parathyroid hormone assay in patients with primary hyperparathyroidism and double adenoma J Am Coll Surg 2003;197:739-746.[Medline]
Top
Abstract
Introduction
