Mediastinal parathyroid cyst resected via a cervical incision using video-mediastinoscopy

Abstract

Parathyroid cysts are rare, benign, cystic lesions usually located in the neck region, and those located in the mediastinum are extremely unusual. Traditionally, thoracotomy or sternotomy has been used to resect mediastinal parathyroid cysts, and recently, video-assisted thoracoscopic surgery has also been employed. Here, we describe a case of non-functional mediastinal parathyroid cyst that was successfully resected via a cervical incision using video-mediastinoscopy.

Introduction

Parathyroid cysts are rare, benign, cystic lesions and usually located in the neck region. Mediastinal parathyroid cysts are extremely unusual, fewer than 150 cases having been reported worldwide to date [1–5]. In most cases, parathyroid cysts are asymptomatic and discovered incidentally by roentgenography [1, 2]. Here, we report a case of non-functional mediastinal parathyroid cyst that was treated by resection via a cervical incision using video-mediastinoscopy.

Case report

A 72-year-old asymptomatic woman with no underlying disease consulted our institution for investigation of a rightward shift of the trachea on a chest roentgenogram without any other apparent cause (Fig. 1a). The blood calcium level was normal, and the parathyroid hormone level was not measured. Chest computed tomography (CT) demonstrated a large cystic mass (7 cm in long diameter) with serous liquid at the left side of the trachea, which was shifted laterally due to the mass effect of the cyst (Fig. 1b). On magnetic resonance imaging (MRI), the mass appeared hypointense on T1-weighted images (Fig. 1c) and hyperintense on T2-weighted images (Fig. 1d). Although the patient was asymptomatic and the mass was thought to be a benign cystic lesion, tracheal deviation was demonstrated by chest CT, and there was a high possibility that dyspnea might occur due to the increase in the size of the cyst. Moreover, the possibility of a malignant tumor could not be completely excluded without resection, and the patient wished for surgical removal of the cyst. Surgical resection was therefore performed. Preoperative fine-needle aspiration or CT-guided biopsy is not indicated because of the risk of cellular dissemination in cases of malignant disease.

Fig. 1.

Chest roentgenogram demonstrated rightward shift of the trachea. a Chest computed tomography demonstrated a large cystic mass at the left side of the trachea, which was shifted laterally due to the mass effect of the cyst. b On magnetic resonance imaging (MRI), the mass appeared hypointense on T1-weighted images (c) and hyperintense on T2-weighted images (d)

Although the cystic tumor extended from the left cervix to the middle mediastinum, we attempted to resect it via a cervical incision using video-mediastinoscopy. After induction of general anesthesia, the patient was placed in supine position with the neck extended. A transverse skin incision about 4-cm long was placed slightly cephalad to the supraclavicular fossa. After dividing the anterior cervical muscles, a tight thin-walled cyst was revealed. The content of the cyst was clear and watery fluid (bacterial culture: negative, cytology: class II). The cyst was easily dissected from the surrounding tissues and removed completely. Video-mediastinoscopy was useful for dissection and hemostasis at the site distal from the cervical incision (Fig. 2). Histological study of the resected specimen demonstrated a thin-walled cyst lined by a single layer of cubical cells and scattered nests of parathyroid cells within a fibrous cyst wall (Fig. 3). These pathological findings were compatible with a benign parathyroid cyst. The patient was discharged from hospital on postoperative day 2 with no complications. Currently, 3 years after surgery, there has been no recurrence.

Fig. 2.

Video-mediastinoscopy findings after tumor resection. Trachea (asterisk), left recurrent laryngeal nerve (white arrow head) and esophagus (white arrow) at deep mediastinum were well visible

Fig. 3.

Histological study of the resected specimen demonstrated a thin-walled cyst lined by a single layer of cubical cells and scattered nests of parathyroid cells within a fibrous cyst wall. (Hematoxylin and eosin stain (a) ×20, (b) ×100)

Discussion

Parathyroid cysts are rare cystic lesions whose origin has not been fully elucidated [1–4, 6]. Several theories to explain their etiology have been reported, including (1) fluid accumulation within a parathyroid gland forming a retention cyst, (2) development from a rudimentary fetal complex of gland-like structure derived from parathyroid or thymic tissue (Kursteiner canal), (3) formation through coalescence of preexisting microcysts, (4) cystic degeneration of a parathyroid gland or preexisting adenoma, and (5) formation from the embryologic remnants of the third or fourth branchial cleft [3, 6]. Parathyroid cysts usually arise in the neck, and those arising in the mediastinum account only for about 10% of all parathyroid cysts [1]. It has been postulated that atypically located parathyroid cysts are due to enlargement and descent of cervical parathyroid tissue into the mediastinum due to their weight and intrathoracic negative pressure or formation from heterotopic mediastinal parathyroid glands [3].

Parathyroid cysts are divided into two categories: functional and non-functional. Functional parathyroid cysts can cause symptoms of hyperparathyroidism such as hypercalcemic crisis and other stigmata of hypercalcemia. Although non-functional parathyroid cysts are mostly asymptomatic, dyspnea resulting from tracheal deviation or narrowing, dysphagia due to esophageal compression, and hoarseness due to impingement upon the recurrent laryngeal nerve are the most commonly reported symptoms arising from large mediastinal parathyroid cysts [1, 6]. In this case, tracheal deviation was demonstrated by chest CT, and there was a high possibility that dyspnea might occur due to the increase in the size of the cyst.

Preoperative diagnosis of parathyroid cyst is usually based on the findings of CT, MRI, and laboratory tests, and the patient’s symptoms [2, 6, 7]. However, preoperative diagnosis of parathyroid cyst, especially the non-functional type, can be difficult and definitive diagnosis is usually established only after resection [2, 3]. Fine-needle aspiration has often been performed, and analysis of the level of parathyroid hormone in fluid from the cyst has been used to confirm the diagnosis of cervical parathyroid cyst [1, 5, 8]. However, in cases of mediastinal parathyroid cyst, preoperative fine-needle aspiration or CT-guided biopsy is not indicated because of the high risk of cyst rupture into the pleural space with cellular dissemination in cases of malignant disease [2, 6, 7].

The mainstay of treatment for parathyroid cyst has been resection. All functional parathyroid cysts and non-functional parathyroid cysts causing local symptoms should be removed surgically [2, 6, 9]. The choice of surgical access depends on the location and dimensions of the mass. Up to 20% of patients who have parathyroid cyst extending into the mediastinum can undergo radical resection via the neck [2]. Sternotomy and thoracotomy have traditionally been the preferred approaches for intrathoracic parathyroid cyst, but recently, thoracoscopic surgery has been used with some degree of success [1, 2, 6, 9, 10]. In the present case, resection was performed via a cervical incision. The merit of a cervical approach is that resection can be performed via a single incision, a postoperative thoracic drain is not required, and postoperative intercostal neuralgia does not occur. Moreover, if pleural adhesion is present, a thoracoscopic approach requires exfoliation of adhesions, making the procedure difficult. However, visualization of the caudal side of the cystic tumor via the cervical incision was not good, and there was a potential risk of damaging the phrenic or recurrent laryngeal nerve and lymphatic ducts. Therefore, video-mediastinoscopy was used in combination to obtain a better view of the deep mediastinum, and this was useful for dissection and hemostasis at the site distal from the cervical incision.

In conclusion, we have presented a rare case of non-functional mediastinal parathyroid cyst, which was resected via a cervical incision using video-mediastinoscopy instead of standard thoracotomy or video-assisted thoracoscopic surgery. Although parathyroid cysts are rare lesions, they should be considered in the differential diagnosis of mediastinal cystic tumors. Resection via a cervical incision using video-mediastinoscopy is one of the effective treatment procedures for mediastinal parathyroid cyst.

Compliance with ethical standards

Conflict of interest

All authors declare that they have no conflict of interest.

Statement of human rights

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. For this type of study, formal consent is not required.