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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 52  |  Issue : 1  |  Page : 6-10

Minimally invasive removal of mediastinal ectopic parathyroid glands: A single-center experience


Division of Thoracic Surgery, Chang Gung Memorial Hospital-Linko, Chang Gung University, Taoyuan, Taiwan

Date of Submission29-Mar-2018
Date of Decision25-May-2018
Date of Acceptance18-Jul-2018
Date of Web Publication18-Feb-2019

Correspondence Address:
Dr. Yin-Kai Chao
Division of Thoracic Surgery, Chang Gung Memorial Hospital-Linko, Taoyuan
Taiwan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/fjs.fjs_33_18

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  Abstract 

Background: The last few years have seen the emergence of minimally invasive mediastinal parathyroidectomy. Here, we report our single-center experience with this procedure.
Materials and Methods: Between December 2002 and September 2017, we performed minimally invasive mediastinal parathyroidectomy in 12 patients with primary (n = 4) or secondary (n = 8) hyperparathyroidism (median age: 54.5 years; interquartile range: 50.5 − 62.75 years). The following variables were retrospectively collected from clinical records: demographic characteristics, results of imaging studies, surgical approach, complications, and final pathological diagnosis.
Results: Technetium-99 m sestamibi examinations were performed for preoperative localization of the ectopic parathyroid glands in 11 patients (91.67%). All cases successfully underwent minimally invasive mediastinal parathyroidectomy, without the necessity to convert to open surgery. The most commonly used minimally invasive approach was video-assisted thoracoscopic surgery (n = 10; 83.33%) followed by mediastinoscopy (n = 2; 16.67%). The anatomical locations of the ectopic glands were as follows: intrathymic in six patients (50%), within the aortopulmonary window in 1 patient (8%), and in other intrathoracic sites in five patients (42%). Parathyroid adenomas and parathyroid hyperplasias were diagnosed in 5 (42%) and seven patients (58%), respectively. There were no perioperative deaths, and the median length of hospital stay was 5.5 days.
Conclusion: Minimally invasive removal of mediastinal ectopic parathyroid glands is safe and feasible if their anatomical position is accurately determined. Surgical approaches depend on gland location and the surgeon's preference.

Keywords: Mediastinal parathyroid glands, minimally invasive surgery, video-assisted thoracoscopic surgery


How to cite this article:
Chou PL, Chao YK, Liu YH. Minimally invasive removal of mediastinal ectopic parathyroid glands: A single-center experience. Formos J Surg 2019;52:6-10

How to cite this URL:
Chou PL, Chao YK, Liu YH. Minimally invasive removal of mediastinal ectopic parathyroid glands: A single-center experience. Formos J Surg [serial online] 2019 [cited 2019 May 25];52:6-10. Available from: http://www.e-fjs.org/text.asp?2019/52/1/6/250868


  Introduction Top


Although ectopic mediastinal parathyroid adenomas or hyperplasias are responsible for up to 25% of hyperparathyroidism cases, only 2% of all abnormal parathyroid glands can be removed through a cervical incision.[1],[2] Under these circumstances, the median sternotomy or thoracotomy are considered the procedures of choice. Unfortunately, intraoperative localization failure is common after sternotomy (occurring in 33%−40% of all cases), resulting in complication rates as high as 21%.[3],[4] With the advent of detailed computed tomography (CT) imaging and technetium-99 m sestamibi scintigraphy, preoperative lesion localization improved significantly and minimally invasive surgery has become feasible.[5]

Although the last few years have seen the emergence of minimally invasive mediastinal parathyroidectomy, the literature in the field remains scarce, with published studies limited to isolated case reports and small case series.[6],[7],[8] Here, we describe a single-center series of patients who underwent minimally invasive mediastinal parathyroidectomy using either video-assisted thoracoscopic surgery (VATS) or mediastinoscopy. We specifically examined the safety and feasibility of the two techniques. We also sought to identify objective criteria that may guide the selection of patients who might benefit most from a minimally invasive surgical approach.


  Materials and Methods Top


Study sample

This single-center study was conducted at the Division of Thoracic Surgery, Chang Gung Memorial Hospital-Linko (Taiwan). Ethical approval was granted by the local Institutional Review Board (CGMHIRB-201800518B0). Between December 2002 and September 2017, we performed minimally invasive mediastinal parathyroidectomy in 12 patients diagnosed with primary (n = 4) or secondary (n = 8) hyperparathyroidism (median age: 54.5 years; interquartile range [IQR]: 50.5 − 62.75 years). Before surgery, patients underwent at least one of the following examinations: (1) technetium-99 m sestamibi scintigraphy, (2) neck ultrasound, (3) CT of the neck and chest, and (4) measurements of serum intact parathyroid hormone (iPTH) levels. The following variables were retrospectively collected from clinical records as follows: demographic characteristics, results of imaging studies, surgical approach, complications, and final pathological diagnosis.

Selection of surgical approach

Once the presence of ectopic mediastinal parathyroid glands was confirmed on imaging studies, patients underwent either VATS or mediastinoscopy. Exploration and resection with mediastinoscopy were considered the procedure of choice when preoperative imaging revealed that ectopic parathyroid glands were located as follows: (1) in the anterior mediastinum within 4 cm from the sternal notch or (2) within the middle mediastinum. In contrast, VATS was performed when the ectopic glands were localized either in the lower anterior mediastinum or in a position of the middle mediastinum which was difficult to be accessed through mediastinoscopy. The decision to perform right-sided or left-sided VATS was similarly guided by preoperative parathyroid gland localization on CT images. Following lung isolation with a double-lumen endotracheal tube, the patient was propped up by 30° in a semi-supine position with a roll placed under the shoulder. The ipsilateral arm was held abducted over a padded L screen and the axilla was exposed for port placement. A total of one to three 10-mm ports were inserted. If the ectopic glands were located in the anterior mediastinum, thymectomy, and excision of mediastinal fat were performed. Patients with ectopic glands localized in a part of the middle mediastinum which was difficult to be accessed through mediastinoscopy underwent VATS without removal of thymus and mediastinal fat. The ectopic glands were removed from the thorax inside an Endo Catch bag (Covidien, Mansfield, MA, USA) through a 10-mm port. In the majority of cases, the removed specimens were submitted to frozen section examination. After hemostasis was achieved, the lung was reexpanded and a chest tube was left in place.

Data analysis

Continuous data are summarized as medians and IQRs, whereas categorical variables are expressed as counts and percentages. All calculations were performed with the Statistical Package for the Social Sciences (SPSS), version 20 (IBM, Armonk, NY, USA).


  Results Top


The general characteristics of the 12 study patients (4 with primary and 8 with secondary hyperparathyroidism) are depicted in [Table 1]. Median levels of iPTH and calcium on preoperative laboratory workup were 1356 pg/mL and 11.1 mg/dL, respectively. Of cases with secondary hyperparathyroidism (n = 8), seven had previously undergone neck exploration for parathyroidectomy. All of them showed persistent or recurrent hyperparathyroidism owing to the presence of hypertrophic mediastinal parathyroid glands. In the remaining patient, gland removal via cervical approach was attempted before proceeding on the same day to minimally invasive removal of mediastinal glands through VATS.
Table 1: General characteristics of the 12 study patients

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Pre-, peri-, and post-operative data are summarized in [Table 2]. Preoperative technetium-99 m sestamibi scintigraphy was used to localize the ectopic glands in 11 patients (91.67%). CT of the chest and neck was performed in all cases. [Figure 1] illustrates the anatomical localizations of the ectopic parathyroid glands.
Table 2: Preoperative imaging findings and perioperative outcomes of the 12 study patients

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Figure 1: Surgical approaches used for excision of ectopic parathyroid glands according to their anatomical location

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Two patients (cases #3 and #4) had ectopic glands located in the mediastinum within 4 cm from the sternal notch; both of them were successfully treated with conventional mediastinoscopy. The remaining 10 patients with ectopic glands located deeply in the mediastinum (below the aortic arch level) successfully underwent VATS.

All of the study participants were extubated in the operating room. There were no perioperative deaths, and the median length of hospital stay was 5.5 days (IQR: 3 − 6 days). As far as postoperative complications are concerned, one patient experienced bleeding that required a second VATS on the postoperative day 9 for evacuation of blood clots (resulting in a prolonged 17-days hospital stay). The results of pathology revealed parathyroid adenomas and parathyroid hyperplasias in 5 (42%) and 7 patients (58%), respectively.

All patients had postoperative iPTH levels within the normal range and remained disease-free at follow-up, the only exception being a case with secondary hyperparathyroidism. The latter patient did not undergo additional follow-up because of another systemic disease associated with general weakness.


  Discussion Top


Major improvements to imaging technologies for the preoperative localization of ectopic parathyroid glands have made it possible to implement highly effective, minimally invasive surgical options. In accordance with previously published studies, all of the patients with ectopic parathyroid glands included in this case series were successfully treated with minimally invasive approaches, without necessity to convert to open surgery.[6],[7],[8] A new and important finding in the current study is the identification of objective criteria to select patients who might benefit most from a minimally invasive surgical approach.[9] Specifically, our current experience suggests that the aortic arch on horizontal chest CT images may serve as a suitable guide for the use of cervical mediastinoscopy versus VATS. Specifically, ectopic parathyroid glands located above the aortic arch and within 4 cm of the sternal notch in the superior mediastinum can successfully be removed through a transcervical mediastinoscopy-assisted approach [Figure 2]. In contrast, ectopic mediastinal glands with other locations should preferentially be treated transthoracically with VATS [Figure 3]. In general, a final treatment decision should be made after thorough consultation between endocrine and thoracic surgeons experienced in VATS.
Figure 2: Computed tomography (a) and technetium-99 m sestamibi scintigraphy (b) showed an enlarged parathyroid gland in the pretracheal region between the common carotid arteries. (c) Gross view of the mass after removal via mediastinoscopy

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Figure 3: Computed tomography (a) and technetium-99 m sestamibi scintigraphy (b) showed an intrathymic left nodule. (c) The patient underwent thoracoscopic thymectomy and the pathological diagnosis revealed an adenoma

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Ectopic mediastinal parathyroid glands are generally located within or close to the thymus (as expected based on the common embryological origin of the two organs).[6],[7],[8],[10] Under these circumstances, total VATS thymectomy is the procedure of choice for the radical removal of ectopic parathyroid glands. On the right side, ectopic parathyroid tissue can also be found in the paratracheal position within the superior triangle (bound by the superior vena cava, the azygos vein, and the vagus nerve). The triangle contains the fibro-fatty-nodal block that comprises R2 − 4 nodal stations. On the left side, it is most commonly located in the aorto-pulmonary window. Owing to their soft texture and lack of calcification, ectopic parathyroid glands located in such anatomical positions may erroneously be considered as a lymph node. In dubious cases, a rapid intraoperative iPTH assay is recommended.[11] Owing to its very short half-life (<5 min), intraoperative measurements of iPTH are clinically feasible. According to the Miami criteria, an iPTH decrease by at least 50% (compared with preoperative levels) at 10 min after removal of suspected ectopic parathyroid tissue supports successful resection.

Ectopic parathyroid adenomas might occasionally present as cystic lesions.[12],[13] Under these circumstances, extra care should be taken to avoid intraoperative injury to the cyst walls. For example, direct traction on the cyst must be avoided and the surrounding soft tissue should be dissected to maintain an adequate distance from the lesion. After tumor removal, the use of a retrieval bag is recommended. All of these procedures do actually minimize the chance of the cystic content being spilled into the mediastinal and pleural cavity (an event which has been shown to increase the risk of disease recurrence because of iatrogenic parathyroid implantation).[14],[15]

Our study is limited by the small sample size and its retrospective nature. One known caveat of retrospective analyses is that the validity of the results depends on accurate medical records. These limitations notwithstanding, our data clearly indicate that recent advances in imaging modalities and operative techniques have allowed radical changes in the surgical management of ectopic mediastinal parathyroid glands. We are currently witnessing a surge of interest in minimally invasive approaches, which will hopefully become the standard of care in the near future.


  Conclusion Top


Minimally invasive removal of mediastinal ectopic parathyroid glands is safe and feasible if their anatomical position is accurately determined. Surgical approaches depend on the gland location and the surgeon's preference.

Acknowledgment

This study was financially supported by a grant (CORPG3G0801) from the Chang Gung Memorial Hospital, Taiwan.

Financial support and sponsorship

This study was financially supported by a grant from the Chang Gung Memorial Hospital, Taiwan.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Prinz RA, Lonchyna V, Carnaille B, Wurtz A, Proye C. Thoracoscopic excision of enlarged mediastinal parathyroid glands. Surgery 1994;116:999-1004.  Back to cited text no. 1
    
2.
Soler R, Bargiela A, Cordido F, Aguilera C, Argüeso R, Cao I. MRI of mediastinal parathyroid cystic adenoma causing hyperparathyroidism. J Comput Assist Tomogr 1996;20:166-8.  Back to cited text no. 2
    
3.
Downey NJ, McGuigan JA, Dolan SJ, Russell CF. Median sternotomy for parathyroid adenoma. Ir J Med Sci 1999;168:13-6.  Back to cited text no. 3
    
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Conn J, Goncalves M, Mansour K, McGarity W. The mediastinal parathyroid. Am Surg 1991;57:62-6.  Back to cited text no. 4
    
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Adams BK, Devi RT, Al-Haider ZY. Tc-99m sestamibi localization of an ectopic mediastinal parathyroid tumor in a patient with primary hyperparathyroidism. Clin Nucl Med 2004;29:388-9.  Back to cited text no. 5
    
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Alesina PF, Moka D, Mahlstedt J, Walz MK. Thoracoscopic removal of mediastinal hyperfunctioning parathyroid glands: Personal experience and review of the literature. World J Surg 2008;32:224-31.  Back to cited text no. 6
    
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Randone B, Costi R, Scatton O, Fulla Y, Bertagna X, Soubrane O, et al. Thoracoscopic removal of mediastinal parathyroid glands: A critical appraisal of an emerging technique. Ann Surg 2010;251:717-21.  Back to cited text no. 7
    
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Kim YS, Kim J, Shin S. Thoracoscopic removal of ectopic mediastinal parathyroid adenoma. Korean J Thorac Cardiovasc Surg 2014;47:317-9.  Back to cited text no. 8
    
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Wei B, Inabnet W, Lee JA, Sonett JR. Optimizing the minimally invasive approach to mediastinal parathyroid adenomas. Ann Thorac Surg 2011;92:1012-7.  Back to cited text no. 9
    
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Gilmour J. The embryology of the parathyroid glands, the thymus and certain associated rudiments. J Pathol 1937;45:507-22.  Back to cited text no. 10
    
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Wild JL, Weigel T, Chen H. The need for intraoperative parathyroid hormone monitoring during radioguided parathyroidectomy by video-assisted thoracoscopy (VATS). Clin Nucl Med 2006;31:9-12.  Back to cited text no. 11
    
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McCoy KL, Yim JH, Zuckerbraun BS, Ogilvie JB, Peel RL, Carty SE. Cystic parathyroid lesions: Functional and nonfunctional parathyroid cysts. Arch Surg 2009;144:52-6.  Back to cited text no. 12
    
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Johnson NA, Yip L, Tublin ME. Cystic parathyroid adenoma: Sonographic features and correlation with 99mTc-sestamibi SPECT findings. AJR Am J Roentgenol 2010;195:1385-90.  Back to cited text no. 13
    
14.
Hage MP, Salti I, El-Hajj Fuleihan G. Parathyromatosis: A rare yet problematic etiology of recurrent and persistent hyperparathyroidism. Metabolism 2012;61:762-75.  Back to cited text no. 14
    
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Rattner DW, Marrone GC, Kasdon E, Silen W. Recurrent hyperparathyroidism due to implantation of parathyroid tissue. Am J Surg 1985;149:745-8.  Back to cited text no. 15
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

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