Ann Thorac Surg 2007;84:1754-1756. doi:10.1016/j.athoracsur.2007.05.055
© 2007 The Society of Thoracic Surgeons
Case Reports
Excision of Postesophageal Parathyroid Adenoma in Posterior Mediastinum With Intraoperative 99mTechnetium Sestamibi Scanning
Toshihisa Ogawa, MD, PhD*,
Ei-ichi Tsuji, MD,
Hajime Kanauchi, MD, PhD,
Kazuhiko Yamada, MD,
Yoshikazu Mimura, MD, PhD,
Michio Kaminishi, MD, PhD
Department of Endocrine Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
Accepted for publication May 7, 2007.
* Address correspondence to Dr Ogawa, Department of Endocrine Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan (Email: e05021{at}h.u-tokyo.ac.jp).
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Abstract
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Although approximately 25% of parathyroid tumors in patients with primary hyperparathyroidism are located in the mediastinum, nearly all these tumors can be removed through cervical exploration. However, 1% to 2% of the mediastinal tumors require a transthoracic approach for removal. The mediastinal tumors are usually located in the inferior parathyroid gland, and the ectopic mediastinal tumors derived from the superior glands are extremely rare. We present a case of retroesophageal mediastinal parathyroid adenoma that developed in the left superior parathyroid gland. A thoracotomy was required to remove this tumor. Radioisotope-guided surgery was effective at identifying the tumor.
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Introduction
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Although most pathologic parathyroid glands can be removed through cervical exploration, approximately 1% to 2% of lesions from ectopic mediastinal parathyroid glands can not be extracted using this approach [1]. Because 70% of the ectopic parathyroid glands are located in the thymus, they can be removed through a cervical approach with or without a sternotomy [2]. Rarely, the ectopic glands located deep in the mediastinum require a thoracotomy for removal. In these cases, it is not easy to intraoperatively identify an ectopic gland. We report here an extremely rare case of a posterior mediastinal retroesophageal ectopic parathyroid adenoma that developed in the left superior parathyroid gland. The patient underwent a thoracotomy for the removal of an ectopic parathyroid adenoma deep in the mediastinum through a radioisotope-guided surgery after the preoperative infusion of 99mTechnetium sestamibi (99mTc-MIBI).
A 72-year-old unconscious woman with hypercalcemia was referred to our hospital in February 2005 for further endocrine evaluation. Her serum calcium and intact parathyroid hormone concentrations were 12.5 mg/dL and 650 pg/mL, respectively. A diagnosis of primary hyperparathyroidism was made. Ultrasonographic examination of the neck showed a small hypoechoic nodule in the left inferior and posterior region of the thyroid gland. However a suspicious lesion was not detected by computed tomographic scan. 99mTc-MIBI scintigraphy showed an abnormal accumulation in the left upper mediastinum; therefore a sternotomy was performed to explore the neck. A normal left inferior parathyroid gland, located behind the lower thyroid pole, and a benign follicular adenoma on the left lobe of the thyroid gland were removed. Exploration of the neck, thymus, and left carotid sheath failed to reveal the left superior parathyroid gland. Pathologic examination of the tissues that were removed showed normal parathyroid tissue and adenomatous nodules in a normal thyroid gland. After surgery the patient’s serum calcium concentration remained at 12.0 mg/dL, and an abnormal accumulation of MIBI at the left upper mediastinum remained (Fig 1). Because we failed to detect the tumor on the initial routine computed tomographic scan, multi-slice computed tomography with three-dimensional reconstruction was performed after the first operation. The second computed tomographic scan revealed a flat 3-cm tumor behind the thoracic esophagus, which was considered an ectopic parathyroid adenoma derived from the left superior parathyroid gland (Fig 2). A right-sided thoracotomy was performed to explore the mediastinum. An enlarged parathyroid gland weighing 4,250 mg, situated behind the thoracic esophagus, was easily detected with the use of a gamma probe after the administration of 99mTc-MIBI, and the tumor was removed with a 3-cm mediastinal incision (Fig 3). A pathologic diagnosis of parathyroid adenoma was made. The patient’s plasma calcium and intact parathyroid hormone concentrations were normalized after the removal of the parathyroid adenoma. The patient was discharged from the hospital on postoperative day 7.
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Fig 1. 99mTechnetium sestamibi scintigram showing intense accumulation of the radioisotope in the left upper mediastinum.
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Fig 2. Computed tomographic scan showing an ectopic parathyroid adenoma posterior to the esophagus (between black arrows in A and at white arrow in B).
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Fig 3. (Top) radioisotope-guided navigation system with gamma probe. (Bottom) intraoperative photograph showing the ectopic parathyroid adenoma in the posterior superior mediastinum.
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Comment
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Although the parathyroid tissue is located in the mediastinum in 11% to 25% of all patients, most parathyroid glands in hyperparathyroidism can be removed through a standard cervical exploration. Clark [3] described 64 mediastinal parathyroid tumors in 285 patients with hyperparathyroidism, 56 (88%) of which could be removed through a cervical incision. Most ectopic parathyroid glands in the lower parathyroid gland or supernumerary gland are located in the thymus [4], or usually in the cervical tongue of the thymus in the anterior mediastinum. Most tumors in the thymus can be removed through a standard cervical incision; however some tumors situated deep in the thymus or mediastinum require median sternotomy for removal. Russel and colleagues [5] reported the removal of mediastinal parathyroid tumors through a median sternotomy in 38 of 2,770 patients (1.4%) with hyperparathyroidism at the Mayo Clinic between 1942 and 1980.
The superior parathyroid glands are usually located within a circumscribed area (2 cm in diameter) approximately 1 cm above the intersection of the recurrent laryngeal nerve and the inferior thyroid artery [4]. However, 1% of the superior glands are located on the lateral surface of the esophagus or in the posterior mediastinum or retropharyngeal space. Rarely the superior parathyroid is located in the thyroid parenchyma. In such a case, hemi-thyroidectomy may be required to remove an intrathyroidal parathyroid adenoma. Russel and colleagues [5] reported that of 2,770 patients with hyperparathyroidism, only one tumor that was found alongside the esophagus in the posterior mediastinum was located in the superior parathyroid gland. Therefore superior parathyroid adenoma in the retroesophageal space in the retromediastinum is considered to be extremely rare. They concluded that in this case the superior parathyroid gland had descended along the tracheoesophageal groove after enlargement [5]. An enlarged gland can descend into the mediastinum because of its increased weight as a result of intrathoracic negative pressure and esophageal movement [6]. In the present case we consider that the tumor in the retroesophageal space in the retromediastinum was derived from the superior parathyroid gland, because during the first operation, the left inferior gland, posterior to the lower thyroid lobe, had been removed.
Because most parathyroid tumors remain within or adjacent to the thymus, they can be removed with a transcervical thymectomy [7]. However, 1% to 2% of mediastinal parathyroid glands, including that in the present case, can not be extracted through a cervical approach [1] because the glands are located deep in the posterior mediastinum, aortopulmonary window, and pericardium. In such cases, a transthoracic approach is needed to remove the tumors. Although the patient in the present case underwent a conventional surgical procedure because of pleural adhesion, the benefit of minimally invasive thoracoscopic surgery for resection of mediastinal ectopic parathyroid tumors was originally proposed in 1994 [8]. These studies indicate that thoracoscopic excision of ectopic parathyroid tumors is less invasive than the other procedures and is associated with fewer complications, shorter hospital stays, a lower incidence of postoperative neuralgia, and fewer cosmetic problems. Thus it is not surprising that thoracoscopic surgery for mediastinal tumors resection has become increasingly popular.
Recent advances in computed tomography and magnetic resonance imaging with three-dimensional reconstruction and the excellent specificity of 99mTc-MIBI scintigraphy for parathyroid tumors have enabled the precise localization of mediastinal parathyroid adenomas. Especially 99mTc-MIBI scintigraphy with multidirectional view, including the lateral view, is indispensable to identify the retromediastinal parathyroid tumors. However, occasionally it is not easy to identify the precise location of parathyroid tumors during surgery. Radioisotope-guided navigation with the use of gamma probes targeting 99mTc-MIBI has been used to identify the precise location of parathyroid tumors since 1997 [9], and the usefulness of this procedure has been reported. In the present case we were able to locate the tumor quickly and dissect it safely using this approach.
In conclusion, we present a rare case of ectopic mediastinal parathyroid adenoma located in the retroesophageal space in the left superior parathyroid gland. Thoracotomy was required to remove this tumor. Computed tomography with a three-dimensional reconstruction image was useful to identify such a tumor in the retromediastinum. Accurate and prompt identification and successful dissection of the tumor were achieved using the intraoperative 99mTc-MIBI navigation system.
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References
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Abstract
Introduction
