Management of cervical bronchogenic cyst via minimally invasive video-assisted thyroidectomy: a report of two cases

Introduction

Bronchogenic cysts are a rare congenital anomaly arising from aberrant budding of the embryonic foregut diverticulum. The estimated incidence ranges from 1/42,000 to 1/68,000 (1). Based on where it occurs, it can be categorized as mediastinal, intrapulmonary, or ectopic types. In the lungs and mediastinum, patients account for almost 99% of cases. Bronchogenic cysts may also appear in rare sites such as the abdomen, spinal canal, and intracranial region. Less than 1%, however, impacts the thyroid or peri-thyroidal regions. The anatomy of the neck is complex. And there are numerous conditions that require a differential diagnosis. The lack of distinctive features in preoperative imaging studies or biopsy results poses challenges in establishing a preoperative diagnosis of bronchogenic cysts in the head and neck region (2). Since most bronchogenic cysts are asymptomatic in adults, many of them are detected during the diagnosis of other diseases. The treatment of asymptomatic cervical bronchogenic cysts remains unclear. According to current reports, few of the operations in the thyroid region use minimally invasive video-assisted thyroidectomy (MIVAT) (3). In the 1990s, Miccoli performed the first MIVAT, which gradually gained widespread acceptance as a technique (4). MIVAT provides surgeons with magnified vision through an endoscopic view, facilitating easier identification of vital structures within the confined space of the neck (5). In comparison to conventional thyroidectomy, MIVAT is a safe and effective procedure for treating both benign diseases and malignant nodules, particularly low and intermediate-risk differentiated thyroid carcinoma. Additionally, this technique yields better cosmetic outcomes and reduces post-operative pain (6).

Here, we report two cases of distinctly different bronchogenic cysts located in the thyroid region. This analysis aims to offer diagnostic insights by examining the shared and distinct characteristics observed in these two surgical cases. We present this article in accordance with the CARE reporting checklist (available at https://gs.amegroups.com/article/view/10.21037/gs-24-301/rc).

Case presentation

Case 1

A 24-year-old male presented with a neck mass persisting for 2 weeks. Upon physical examination, a significant non-pulsatile and firm mass was detected in the right cervical region, exhibiting mobility during swallowing. Ultrasonography (US) revealed a cyst measuring approximately 41 mm × 18 mm in the right inferior thyroid area (Figure 1). Computed tomography (CT) imaging of the neck demonstrated diffuse enlargement of the right thyroid lobe. The right thyroid gland and trachea were deviated to the left side (Figure 2). The patient’s thyroid hormone levels were within normal range. Notably, the patient remained asymptomatic without any signs of hoarseness or dysphagia while drinking. Despite the patient’s asymptomatic condition, a palpable mass was clearly evident in his neck. Consequently, the patient expressed a strong desire for surgery due to aesthetic concerns. Based on these aforementioned findings, the initial diagnosis of a thyroid cyst was made.

Figure 1 US of case 1. (A) US showing a 4.1-cm cystic mass in the right inferior thyroid area. (B) The normal right thyroid lobe was compressed by the cyst (arrow). US, ultrasonography.

Figure 2 Axial CT view of case 1 showing the tracheal (yellow arrow) was compressed to the left side by the cystic mass (white arrow). CT, computed tomography.

MIVAT was performed. A 2 cm-long incision was made in an existing skin line of the lower neck. The anterior cervical fascia was dissected along the midline, establishing a space between the superficial sternothyroid muscles. The sternothyroid muscle was separated along the linea alba of the neck, and dissection of the thyroid surgical membrane space allowed for the separation of loose connective tissue within it. Intraoperative findings revealed that the mass was located deep beneath the thyroid gland, exerting pressure on adjacent thyroid tissue. There was a distinct border between the cyst and the right thyroid lobe, with small blood vessels running through its surface. On further examination, thick veins were observed extending from the lower pole of the thyroid along the tracheal surface on the medial aspect of the cyst. However, no obvious donor vessels were identified on the cyst’s surface (Figure 3). After considering that the cyst’s location was superficial, it was unnecessary to expose the recurrent laryngeal nerve during the procedure, thereby ensuring the preservation of this crucial anatomical structure.

Figure 3 Intraoperative condition of case 1. (A) Location between right normal thyroid lobe and the cystic mass; (B) the veins adjacent to the trachea on the medial side of the cyst undergo compression and compensatory dilatation; (C) grayish-brown mucus in the cyst.

The cyst was subjected to intraoperative fenestration decompression due to its excessive size, which could potentially impede the surgical field of view. By utilizing precise dissection techniques, complete removal of the cyst was achieved. Intraoperatively, the cyst had a smooth wall with a viscous grayish-brown mucus was observed. Postoperative pathology revealed a cystic structure lined with pseudo-compound ciliated columnar epithelium, while the cyst wall consisted of fibers and smooth muscle with banded lymphocyte infiltration and a few plasma mucus glands, leading to the diagnosis of bronchogenic cyst (Figure 4). The patient experienced an uneventful postoperative recovery without using antibiotics and was discharged on the following day. One month later, an ultrasound examination demonstrated that the right thyroid lobe, previously compressed before surgery, had regained similar dimensions as the left lobe. The reexamination of thyroid function results was all within normal levels. The patient recovered well without any discomfort.

Figure 4 Histopathological examination. In case 1, the cysts are lined by respiratory type epithelium, which is characterized by pseudostratified columnar cells and cilia (H&E stain, 20×). Pseudo-compound ciliated columnar epithelium indicated by arrow. Smooth muscle indicated by *. H&E, hematoxylin and eosin.

Case 2

A 36-year-old male without obvious symptoms was diagnosed with right papillary thyroid cancer by ultrasound-guided fine needle aspiration cytology for 2 months. The preoperative neck ultrasound and CT scans revealed a mass measuring approximately 70 mm × 73 mm arising from the right lower middle lobe of the thyroid gland. Therefore, the minimally invasive video-assisted right total thyroidectomy and prophylactic central neck dissection were decided to be performed.

Incidentally, a 3 mm × 3 mm mass containing mucus fluid was observed at the upper pole of the right thyroid lobe during the procedure (Figure 5). Considering the possibility of tuberculous spheres or metastatic lymph nodes, we decided to resect the mass. During ultrasonic knife resection, we observed the presence of grayish-brown mucus exudate, which was subsequently collected for afterward bacterial culture analysis. During the operation, the nerve monitor detected no diminished nerve signal in the right laryngeal recurrent nerve. The operation was successfully completed. However, after reviewing the surgical video post-operation, it was observed that due to excessive tension on the upper pole of the thyroid gland, there was an upward retraction of a part of the cyst wall during the resection process, resulting in incomplete removal of said cyst wall.

Figure 5 Intraoperative condition of case 2. (A,B) The cyst was located at the upper pole of the right thyroid lobe.

Postoperative pathology showed the results were papillary thyroid cancer (with prelaryngeal lymph node metastases for one out of seven and central lymph node metastases for five out of seven) and bronchogenic cyst (pseudostratified ciliated columnar epithelium is visible) (Figure 6). The bacterial culture results were negative. The patient did not use any antibiotics post-operatively. And did not experience postoperative pyrexia, hoarseness, or any other additional discomforts. Up to now, there have been no indications of recurrence.

Figure 6 Histopathological examination of case 2, the wall of certain bronchogenic cysts is contiguous with normal thyroid follicular tissue [H&E stain, 10× (A) and 5× (B)]. Pseudo-compound ciliated columnar epithelium indicated by arrow. H&E, hematoxylin and eosin.

All procedures performed in this study were in accordance with the ethical standards of the Ethics Committee of Capital Medical University (No. 2017049X) and with the Declaration of Helsinki (as revised in 2013). Written informed consent was obtained from the patients for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

Bronchogenic cysts are an uncommon congenital anomaly that arises from abnormal budding of the pre-intestinal diverticulum during embryonic development. The foregut undergoes dichotomous development during the third week of embryonic development, followed by the emergence of a ventral diverticulum that gives rise to the trachea. During this procedure, developmental anomalies and aberrant cellular division can lead to the formation of bronchogenic cysts. These cysts could appear along the middle compartment of the mediastinum or within the posterior mediastinum close to the esophagus (7). Typical bronchogenic cysts have four main locations: inferior paratracheal area, hilar area, bronchial bifurcation, and inferior pulmonary ligaments. Cervical bronchogenic cyst is more commonly reported in the pediatric population, but rare in adults (8). The male-to-female ratio is 4:1 (9).

Most of the bronchogenic cysts are asymptomatic. The larger bronchogenic cysts may present with common symptoms such as stridor, dyspnea, and dysphagia. Preoperative imaging examinations including US, CT, and magnetic resonance imaging (MRI) can assist in diagnosing bronchogenic cysts. CT can reveal the contents of the cyst which mainly consist of varying proportions of water and protein. MRI demonstrates high signal intensity on T2-weighted images for bronchogenic cysts and aids in distinguishing cysts from soft tissue detail. Imaging methods clearly visualize the relationship between cysts and important neck structures (1). It is quite crucial for surgical planning. However, it is challenging to differentiate bronchogenic cysts from other cervical cystic diseases based solely on imaging features preoperatively. Cervical bronchogenic cysts should be differentiated from branchial cleft cysts, thyroglossal duct cysts, thymic and thyroid cysts, dermoid and lymphangiomas, cystic hygromas, teratomas, and cystic neuromas through examination. Histopathological examination remains the golden standard for diagnosing bronchogenic cysts. Bronchogenic cysts are characterized by a pseudostratified, ciliated, columnar epithelial lining with underlying seromucous glands.

Recently, the management of asymptomatic cysts in adults remains a subject of controversy (2). Although bronchogenic cysts are benign, certain reports have suggested that complete excision is necessary from two perspectives. On the one hand, it can prevent potential complications such as infection, rupture, and malignant transformation. Generally, bronchogenic cysts are unilocular, contain fluid, and lack communication with the airways. However, if the cyst is located superficially or extends deeply, it may form a fistulous tract with skin or trachea. This may lead to a postoperative infection (10,11). In case 2, the bacterial culture results of the cyst fluid verified that the mucus was sterile. And both two patients recovered without using antibiotics postoperatively. Therefore, it is recommended that cyst rupture alone intraoperatively does not necessarily lead to infection. Thorough and repetitive wound irrigation should be performed to minimize implantation caused by leakage of sac fluid. However, when there is close adherence between the cyst and trachea, a meticulous examination for air leakage should be conducted to prevent other potential complications. In addition, according to our intraoperative observation, the bronchogenic cysts both contain typical grayish-brown color mucus, which is seldom described in existing case reports. Thus, we considered this might be the characteristic mucus of bronchogenic cysts. The first documented case of a poorly differentiated adenocarcinoma arising from a bronchogenic cyst in the cervical region was reported in 2011 (12). Thus, complete excision of the cysts is important.

On the other hand, complete excision of cervical bronchogenic cysts is also important for preventing recurrence. The chondroid tissue at the base of the cysts should also be completely resected. Researchers revealed that one pediatric patient experienced recurrence due to incomplete removal of the chondroid tissue during the initial operation (1). Besides, small bronchogenic cysts bear a resemblance to lymph nodes, which are intricately linked to the assessment and prognosis of thyroid cancer. In the previous literature, few reports of video-assisted technology were applied to cervical bronchogenic cysts. Only one reported case has utilized gasless endoscopic resection of neck masses via the axillary approach. However, this operative approach is limited in its ability to perform bilateral thyroidectomy (3). In contrast, MIVAT enables the performance of both bilateral thyroidectomy and cervical lymph node dissection. Also, compared to traditional thyroid surgery, MIVAT is also associated with a minimal incision. The cosmetic outcomes, however, are inferior compared to the axillary approach.

Larger cysts have their own distinct characteristics in terms of the pattern of surrounding blood vessels and their growth patterns. Just like in the first case, if a crossing blood vessel is observed intraoperatively that does not penetrate the mass or an exogenous cyst compresses peripheral blood vessels, it becomes necessary to consider whether the mass originates from the thyroid. The complete removal of asymptomatic cysts is good for preserving thyroid function. In case 1, the cyst seriously compressed the right lobe of the thyroid gland and pushed it towards the head side. One month later, the right thyroid gland was restored to its original position.

Conclusions

The anatomical complexity of the neck necessitates the differentiation of lesions from various neck diseases. Considering the non-specificity of imaging examinations, surgical resection is an effective approach for treating and confirming the diagnosis of bronchogenic cysts while minimizing complications. During surgery, complete cyst removal is essential in order to prevent postoperative recurrence. Given the lack of trustworthy preoperative diagnosis, we advise suitable patients to have all suspected bronchogenic cysts removed via surgery, especially complete excision.

Acknowledgments

Funding: The study was supported by the National Natural Science Foundation of China (No. 62088101).

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://gs.amegroups.com/article/view/10.21037/gs-24-301/rc

Peer Review File: Available at https://gs.amegroups.com/article/view/10.21037/gs-24-301/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://gs.amegroups.com/article/view/10.21037/gs-24-301/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the Ethics Committee of Capital Medical University (No. 2017049X) and with the Declaration of Helsinki (as revised in 2013). Written informed consent was obtained from the patients for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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