DOI: https://doi.org/10.21203/rs.3.rs-757628/v1
Background
Mediastinal teratomas are rare tumors that most frequently occur in the anterior mediastinum. The majority of these tumors are benign and slow growing. Due to their low malignant potential, the treatment for these tumors is surgical resection. The surgical management has shifted from invasive approaches such as a sternotomy to minimally invasive ones such as robotic-assisted thoracoscopic resections. Though many cases of mediastinal teratomas have been reported, we present a rare case of a locally advanced mediastinal teratoma requiring patient repositioning and change in ventilatory management mid-procedure to facilitate complete resection.
Case Presentation
A 43 year-old female was found to have an anterior mediastinal mass during work-up for an intermittent cough in 2009. Chest imaging and biopsy at the time showed evidence of a cystic teratoma without concerning features. She underwent imaging surveillance until 2018, when chest imaging showed increasing growth and worrisome radiologic features concerning for malignant degeneration. She underwent an elective robotic-assisted thoracoscopic resection utilizing double lung ventilation, but due to extensive involvement of the right lung, pericardium, superior vena cava, and right phrenic nerve the patient had to be repositioned and started on single lung ventilation mid-procedure to facilitate a safe and complete resection.
Conclusions
Anterior mediastinal teratomas can be successfully removed by robotic-assisted thoracoscopic resections utilizing single lung ventilation. Though robotic-assisted thoracoscopic resection utilizing double lung ventilation can be effective in performing lung wedge resections and pleural biopsies, it is limited in removing locally advanced mediastinal tumors.
Extra-gonadal teratomas of the mediastinum are very rare tumors that occur most frequently in the anterior mediastinum. The majority of these tumors are benign and slow growing, and as a result, are found incidentally.1–3 Due to their low malignant potential, the treatment for these tumors is surgical resection, which affords excellent long-term disease-free survival.3 Though many cases of mediastinal teratomas have been reported, we present a rare case of a locally advanced mediastinal teratoma requiring an extensive robotic-assisted thoracoscopic resection of the pericardium, lung, superior vena cava, and phrenic nerve. Most of these robotic-assisted resections are performed with the patient in lateral decubitus position and utilizing single lung ventilation. Given the success of double lung ventilation during robotic-assisted thoracoscopic lung wedge resections, we attempted the resection with the patient positioned supine and with double lung ventilation in order to avoid the complications of using a dual-lumen endotracheal tube.
A 43 year-old-female was found to have an anterior mediastinal mass while being worked up for an intermittent cough in 2009. Further workup with computerized tomography (CT) thorax and CT guided percutaneous biopsy showed a benign cystic teratoma with negative tumor markers. The patient subsequently underwent yearly surveillance CT scans. A surveillance CT Thorax done in 2014, showed the anterior mediastinal mass to measure 5.2 x 5.0 x 5.5 cm and composing mostly of fat with some mural calcification and a thickened capsule (Fig. 1A). Subsequent surveillance scans showed a stable mass for which, she presented to our clinic in 2018 for cessation of surveillance. However, repeat CT thorax showed the mass to have enlarged (5.4 x 4.8 x 6.2 cm) with a new lobulation extending to the right of the initial lesion, measuring 15mm (Fig. 1B, 1C). Due to the further increase in size of the mass and new lobulation (15 to 19 mm) (Fig. 1D) there was a concern for malignant degeneration, as such, the plan was for surgical excision of the mass.
The planned procedure was a robotic-assisted thoracoscopic resection via right lateral approach. The patient was brough to the operating room, placed supine, and general anesthesia was started. A single lumen endotracheal tube was used to intubate the patient. The thorax was entered via standard thoracoscopic incisions and a total of 3 8mm ports were used (6th intercostal space in the anterior axillary and mid-clavicular line, and the 4th intercostal space in the anterior axillary line). Upon initial inspection, the mass was adherent to the right upper lobe and the right phrenic nerve. Dissection began medially with a combination of blunt dissection and cautery. The mass was dissected from the anterior chest wall but found to be abutting the innominate vein and densely adhered to the superior vena cava (SVC). The mass was meticulously dissected free from the anterior pericardium, innominate vein, and aortic arch (Fig. 2A). The right phrenic nerve was found to be circumferentially encapsulated by the mass and was sacrificed (Fig. 2B). Anterior dissection was continued until it was deemed difficult to assess the full extent of anterior lung and SVC involvement. The decision was then made to change patient position to left lateral decubitus with additional lateral chest port placement and utilizing single lung ventilation.
The robotic instruments were removed from the patient and the robot was undocked. The single lumen endotracheal intubation was exchanged for a double lumen endotracheal tube to facilitate single lung ventilation. The patient was then placed in the left lateral decubitus position. Four additional 8mm ports were placed along the 7th intercostal space and dissection continued posteriorly and laterally. The mass was attached to portions of the right upper and middle lobe, for which 2 wedge resections were done to free the mass from the respective lung lobes (Fig. 2C). The tumor was found to be too adhered to the SVC, as such, a tangential resection of the mass with the SVC was done with a vascular load using the robotic stapler (Fig. 2D). After the mass was freed circumferentially, it was removed by a specimen bag. After specimen retrieval, a right robotic diaphragmatic plication was done using the initial port incisions, and a 28 French chest tube was left in place.
On gross examination, the tissue specimen was tan-pink in color with a cystic cavity filled with tan-gray gummous material as well as a fatty nodule. Histopathological examination revealed a mature cystic teratoma with an extensive cystic component with negative margins. The patient had an uneventful post-operative course and was discharged on post-operative day 3.
Teratomas are the most common germ cell tumor of the anterior mediastinum. These tumors are often very slow growing and are typically found incidentally on chest x-rays during unassociated work-up.1–4 On CT imaging, they have a heterogenous appearance with images revealing a mass with fluid, fat, and calcification.3 When symptoms do arise, though there are uncommon, they are due to compression of adjacent mediastinal structures. Patients will typically present with symptoms of cough, dyspnea, chest pain, and post-bronchial pneumonia. The treatment of choice is surgical resection, which has shown excellent long-term disease-free survival.2–4
The traditional surgical approach for resection of an anterior mediastinal germ cell tumor has been via a median sternotomy. However, the associated morbidity and mortality associated with a sternotomy has pushed surgeons towards video-assisted thoracoscopic or robotic-assisted thoracoscopic surgery.2 During these procedures patients are often placed in the lateral decubitus or supine positions, with the port placements being more anterior on the chest wall with supine positioning. Though thoracoscopic lung resections are commonly performed with single lung ventilation (SLV), if there is no anticipated lung involvement of the mediastinal mass, then double lung ventilation (DLV) can provide adequate exposure and decrease undesired complications of using a dual lumen endotracheal tube.5 DLV with carbon dioxide insufflation has been typically used for procedures such as thoracoscopic pleural biopsies or lung wedge resections.5,6 A single center retrospective study comparing SLV and DLV for primarily pulmonary wedge and mediastinal mass resections have shown decreased operative time, and time to incision in the DLV group. Moreover, there were no difference in complications such has hemodynamic compromise.7 The hesitancy in applying DLV for more thoracoscopic procedures is mainly attributed to concerns of a tension pneumothorax from carbon dioxide insufflation, but patients were able to tolerate 10-15mmHg of pressure without any hemodynamic compromise.7
Of the patients that undergo resection for mediastinal teratomas, 10–15% require an additional procedure including a lobectomy or pericardiectomy.4 There have not been many reported cases in the literature of anterior mediastinal teratomas involving the lung, phrenic nerve or SVC.4 In this case, the extent of anterior mediastinal involvement of the mass was more than that seen on pre-operative CT scans. Thus, we attempted resection with the patient supine and with DLV in order to facilitate a safe dissection with minimal OR time and without the associated complexity of a dual lumen endotracheal tube. However, after the tumor was found to be involving the anterior upper and middle lung lobes and the SVC, we decided to undock the robot, reposition the patient and use single lung ventilation to better assess the anterior lung involvement and facilitate a safe and complete resection.
There is no consensus on the optimal approach to these tumors but a robotic-assisted thoracoscopic resection is a feasible approach to a benign teratoma. Though DLV has been used for lung wedge resections and pleural biopsies, using DLV during resection of a densely adherent anterior mediastinal mass can make assessing the extent of involvement and safe resection challenging.
CT, SLV, DLV, SVC
Ethics Approval and consent to participate
Written informed consent was obtained from the patient.
Consent for Publication
Written informed consent was obtained from the patient for publication of this case report.
Availability of Data
The data used is available upon request from the corresponding author.
Competing Interests
The authors declare that they have no competing interests.
Funding
Not applicable
Authors Contributions
HR collected the clinical data and drafted the manuscript. JW provided edits to the manuscript. All authors read and approved the final manuscript.
Acknowledgements
Not applicable