Thoracoscopic Excision of Mediastinal Bronchogenic Cysts in Children: A Case Series

Background

Mediastinal cysts are a diverse group of congenital anomalies that present surgeons with a diagnostic challenge and varied modes of treatment and intervention. They result from abnormal foregut and thymus development. Location within the mediastinum is a key element of diagnostic workup and depends on cyst formation timing during development.^1,2 Anterior mediastinal cysts are often thymic or cystic teratomas and demand a high suspicion of malignancy. ³ Pericardial cysts in the middle mediastinum are generally asymptomatic and rarely require intervention. The posterior mediastinum contains foregut duplication cysts with esophageal or intestinal lining, neurenteric cysts associated with the nervous system, and bronchogenic cysts lined respiratory epithelium, often containing smooth muscle and cartilage.^2,3

Congenital bronchogenic cysts develop from anomalous budding of the tracheal diverticulum and develop into a thin-walled, bronchial epithelium-lined, mucus-filled cavity off the tracheobronchial tree, typically located centrally.^2–4 While bronchogenic cysts do not frequently communicate with the airway, they can obstruct or compress the bronchial tree, leading to dilation and hyperinflation in distal lung structures, especially if cysts enlarge, become infected, or present in older children.^4,5 Most remain asymptomatic; however, mass effect can result in respiratory symptoms or chest discomfort. ³

Bronchogenic cysts are frequently diagnosed on prenatal ultrasound as a mediastinal cystic structure, but can be discovered later in life in a child presenting with respiratory symptoms.^2,4 A computed tomography (CT) scan or magnetic resonance imaging (MRI) can be helpful in solidifying diagnosis and surrounding anatomy. Bronchogenic cysts should be excised regardless of symptoms due to the risk of infection, mass effect on adjacent structures, or malignant transformation. ⁵ Asymptomatic newborns undergo elective resection, typically between three and six months of age; however, symptomatic newborns may require immediate intervention following birth.^4,5 Older children with a late diagnosis should have the cyst excised when identified and clinically stable. ⁵

Video-assisted thoracoscopic surgery is the preferred approach for the resection of bronchogenic cysts as thoracotomy is associated with a longer hospital stay, increased postoperative pain, higher rate of wound infection, worse cosmetic results, and musculoskeletal complications, including chest asymmetry and scoliosis.^4,6–9 However, surgeons can be hesitant to utilize a thoracoscopic approach for mediastinal masses due to their proximity to vital structures. This study describes our experience with children presenting with a mediastinal bronchogenic cyst. Preoperative, intraoperative, and postoperative courses were examined to summarize surgical care and evaluate outcomes.

Methods

A single-institution retrospective review evaluated all mediastinal bronchogenic cyst excisions between January 2012 and November 2022. Institutional review board approval was obtained. Baseline demographic variables included age at diagnosis, presenting symptoms, imaging workup, cyst characteristics, and operative approach. Outcomes included intra-operative and postoperative complications, length of stay, and histopathological examination. Statistical analysis was completed by measuring sums and standard measures of central tendency, including the median and range (Microsoft Excel, 2022).

Results

Five patients were identified, who underwent mediastinal bronchogenic cyst excision during this period. Demographics, presenting symptoms, imaging workup and findings, and cyst location are included in Table 1. No patient was diagnosed prenatally. The median age at diagnosis was 23 months (18–27 months). All patients were symptomatic at the time of diagnosis, with symptoms including recurrent respiratory infections, cough, wheezing, and tachypnea. Two patients had a CT scan performed, 1 had an MRI, and 2 underwent both. Cysts were located in the hilar, carinal, paratracheal, and paraesophageal regions. Concerning features on imaging included mainstem bronchus compression and abutment of the aorta, superior vena cava, pulmonary arteries, and esophagus.

All 5 patients' families elected for resection. As all patients were symptomatic at diagnosis, surgery was delayed between four and six weeks, allowing the resolution of acute infectious or inflammatory processes. Age at resection ranged from 26 to 30 months. Operative approach, port placement, technical challenges, unique operative maneuvers, and surgical pathology are highlighted in Table 2. The side of the operative approach was determined by ease of access based on preoperative imaging.

Three cysts were approached from the left chest, while two were approached from the right. Single lung isolation was achieved in 4 cases; 1 patient had mass effect leading to significant narrowing of the left mainstem bronchus, which was prohibitive. Patients were positioned in a lateral decubitus position. Three ports were placed between the anterior and posterior axillary lines in each case. The specific location of individual ports is included in Table 2, with slight adjustments to placement occurring due to the variable location of individual cysts.

Individual technical challenges included significant mediastinal inflammation, the necessity for cyst evacuation to delineate the extent of the cyst, adherence of cyst wall to bronchus or trachea requiring cold dissection, presence of a stalk of tissue with an intimate connection to the carina that was amputated with an endoloop, and presence of the vagus nerve overlying the cyst requiring gentle retraction. All cysts were successfully excised in their entirety through a thoracoscopic approach. A chest tube was left in 4 patients. Three patients had their chest tubes removed on postoperative day one, while 1 had theirs removed on postoperative day two. All patients were discharged home. No intraoperative or postoperative complication was observed. Surgical pathology was consistent with a bronchogenic cyst in all 5 cases. Symptoms resolved in 3 patients and had improved in the other 2 at their last follow-up visit.

Discussion

Mediastinal bronchogenic cysts present a unique challenge to surgeons due to their proximity to vital structures, including the airway, esophagus, mediastinal vessels, vagus nerve, and recurrent laryngeal nerve. The results of this study demonstrate 5 cases of mediastinal bronchogenic cysts that were successfully excised thoracoscopically. We present this case series to illustrate specific technical maneuvers utilized to aid in dissection, which are discussed here.

The posterior mediastinum is usually best approached through a modified prone position, as described in other series. This allows the collapsed lung to drop out of the field of view with more ergonomic angles of dissection.^6,10 Our series and others like it have found aspiration of cyst fluid to be a key technique to improve thoracoscopic visualization and dissection. ¹¹ Although maintaining cyst integrity is initially helpful in delineating the anatomy, large cysts may obstruct structures in the background view. Aspiration of the cyst contents may facilitate appreciation of the extent of the posterior and contralateral cyst walls. Creating multiple windows of dissection around the cyst helps track the layout of multilobed cysts or cysts that insinuate between structures. Gentle retraction on the cyst wall and surrounding structures, such as the pulmonary artery, is essential. Thoracoscopic excision was well tolerated in each case, with no complication observed.

Thoracoscopic resection can be performed safely with equivalent outcomes to the open approach when surgical expertise permits.^4,5 Several retrospective reviews, case series, and case reports have demonstrated that mediastinal masses of varying complexity and location, including bronchogenic cysts, can be successfully managed thoracoscopically, granting patients the benefits of a thoracoscopic approach over open excision.^7,10–13 In addition, we believe that thoracoscopy offers superior visualization compared to an open approach, thus allowing for a safer dissection.

Prior studies have found that a thoracoscopic resection is associated with less postoperative pain, shorter hospitalization and recovery, decreased need for and duration of chest tubes, improved morbidity, and better cosmetic results (smaller scars and lower risk of chest deformity/keloid) compared to an open procedure.^4,7,11,12 In addition, thoracoscopic magnification can benefit dissection and complete excision when the cyst is closely associated with vital structures or in a hard-to-reach location. ¹¹ Specifically, extra care must be taken to avoid accidental injury to the tracheobronchial tree and esophagus, especially when there is a shared wall with the cyst.^10,14 While none of our cases required conversion to thoracotomy, this option is viable if the dissection proves difficult thoracoscopically or if bleeding obscures thoracoscopic visualization. When complete resection is not possible, the mucosal layer should be excised completely to prevent malignancy or recurrence, and lobectomy may be necessary if bronchus obstruction is present. ⁴

Limitations of the study include those inherent to its retrospective nature and the small sample size. Interestingly, all 5 patients were diagnosed following birth, although mediastinal cysts are frequently detected on prenatal ultrasound.^2,4 Since the sample size is small, this finding is most likely due to a sampling error. Given that all patients were symptomatic at the time of diagnosis, we elected to delay surgery for four to six weeks to allow the resolution of acute infectious or inflammatory processes. As there was no clinical evidence of ongoing infection at the time of resection, we did not send microbiology specimens for analysis. No infection occurred after the resections. However, we recommend sending specimens at the time of surgery if any evidence of acute or chronic infection is encountered.

Conclusion

This series confirms and expands upon previous findings that thoracoscopic surgery is safe and effective for the resection of mediastinal bronchogenic cysts, highlighting specific operative techniques that are helpful for challenging dissections.