Robotic Bilateral Approach for Thymoma Involving the Pericardium, Right Phrenic Nerve, and Right Lung

Patient Selection 

This 42-year-old female patient with seropositive myasthenia gravis was receiving treatment with oral prednisone and pyridostigmine. She presented with persistent generalized weakness. Imaging revealed a 9 cm lobulated mass in the right anterior mediastinum. Magnetic mesonance imaging (MRI) indicated a predominantly cystic lesion with soft tissue nodules, highly suspicious for thymoma, without evidence of infiltration into adjacent cardiovascular structures. A positron emission tomography (PET) scan showed low-grade uptake with no signs of metastatic disease. Pulmonary function tests (PFTs) were within normal limits, and an echocardiogram showed no abnormalities. After presenting the case in a multidisciplinary team (MDT) meeting, surgical resection was recommended. 

Operative Steps 

Patient Positioning

The patient was positioned in supine decubitus with inflatable bags placed under each hemithorax, allowing for selective elevation of the surgical side without repositioning or redraping the operative field. The surgery was performed under general anesthesia, with selective orotracheal intubation, intravenous (IV) and arterial lines placed for monitoring, and defibrillator pads applied in anticipation of potential arrhythmias during the procedure. 

Bilateral Robotic Approach 

A triangular port placement was used on each hemithorax, as is standard for robotic thymectomy. A 30-degree camera was positioned in the fifth intercostal space along the anterior axillary line. Carbon dioxide (CO2) insufflation was performed at a preset pressure of 6 to 8 mm Hg, with a flow rate of 6 to 10 liters per minute. The other two ports were placed as follows: one extra-long port in the third intercostal space along the midaxillary line and another port at the fifth or sixth intercostal space along the midclavicular line. Additionally, 5 mL of 0.50 percent bupivacaine was infiltrated into each interspace at the port sites for local anesthesia. 

Left-Sided Dissection 

The dissection began with mobilizing the left pericardial fat and the lower horn of the thymus. The phrenic nerve was identified as a lateral boundary to avoid thermal or mechanical injury. Dissection continued along the pericardium and posterior surface of the sternum toward the left upper horn. Extensive cranial dissection was performed to prevent residual thymic tissue. The innominate vein was exposed to guide safe dissection and complete mobilization of the left thymic lobe. 

Right-Sided Dissection 

A similar robotic approach was performed on the right side, with three 8 mm ports placed. A large, whitish tumor with infiltration of the pericardium, right phrenic nerve, and right upper and middle lobes was visualized. The right thymectomy began by dissecting the right upper horn and mobilizing the thymus from the innominate vein. Small thymic veins draining into the innominate vein were sealed to prevent bleeding. The lower horn was mobilized, and complete exposure of the pericardium was achieved. 

Pericardial Resection and Tumor Removal 

The pericardium was opened circumferentially around the tumor, with careful attention to macroscopic margins. Transection of the right phrenic nerve was necessary due to its involvement with the tumor. The pericardium was carefully resected from the superior vena cava, ensuring the absence of direct cardiac invasion. Tumor resection continued by carefully separating the posterior pericardium from the right pulmonary hilum. The right superior pulmonary vein was closely monitored to avoid injury. The tumor was then detached from the lung parenchyma using endoscopic staplers, ensuring clear margins while preserving healthy lung tissue. 

In this case, pericardial reconstruction with a mesh was not performed because the defect was limited in size and did not compromise cardiac function or hemodynamic stability. Moreover, unlike in pneumonectomy cases, where the absence of the lung leaves the heart unsupported, the presence of the lung helps to contain and support the heart, further reducing the risk of displacement. Avoiding synthetic mesh also minimized the risk of infection. 

Placement of Surgical Clips 

Several metallic clips were applied to the pericardial surgical margins to assist in identifying resection boundaries and to facilitate potential adjuvant radiotherapy treatment. These clips help define the tumor bed for targeted radiotherapy, should it be necessary as part of the patient's postoperative management. 

Final Step 

After full mobilization, the tumor was placed in an endoscopic retrieval bag and safely removed from the thoracic cavity, completing the resection. 

Preference Card 

The surgical instrumentation included the following: the da Vinci Xi robotic platform, 8 mm robotic ports (one of which was extra-large), a 30-degree camera, Cadiere forceps, Maryland forceps, endoscopic tri-staplers (45 mm, purple reload), and an endoscopic clip applier. 

Tips and Pitfalls 

Tips 

1. Starting Dissection on the Contralateral Side 

In cases of large thymomas that are difficult to manipulate and may infiltrate adjacent structures, it is particularly important to start the dissection on the contralateral side. This approach allows for a more straightforward and radical dissection of the thymus on the contralateral side, which can be completed more easily and safely. Once this side is thoroughly dissected, the tumor side can be approached with greater ease and reduced risk of complications. 

2. Phrenic Nerve Identification and Protection 

Always clearly identify the phrenic nerve and use it as a lateral boundary during dissection. This helps avoid thermal or mechanical injury, especially in cases where the contralateral phrenic nerve might be involved with the tumor (as indicated by diaphragmatic elevation in the preoperative chest X-ray). Bilateral phrenic damage will lead to severe respiratory compromise and morbidity. 

3. Pericardium visualization 

In cases with pericardial involvement, it is advisable to preemptively clean the pericardium for better visualization when performing pericardial resection. This involves completely removing all the fat tissue to clearly expose the pericardium. 

Pitfalls 

1. Incomplete dissection of the upper or lower horns of the thymus, including the pericardial fat, can lead to residual tissue, especially in patients with myasthenia gravis. This may lead to suboptimal outcomes or tumor recurrence. It is recommended to perform an extended radical thymectomy, including the thymoma, and to avoid performing only a thymectomy. 

2. During pericardial manipulation, cardiac arrhythmias such as ventricular ectopy may occur. Always have external defibrillator pads available and be ready for intervention if necessary. 

3. Careful attention must be given to the vascular structures, particularly the superior vena cava, right atrium, and right pulmonary vein, when performing pericardial dissection and tumor removal. Damage of these structures can lead to fatal bleeding. Therefore, a sternotomy set should be always ready. 

References

1. Kneuertz PJ, Kamel MK, Stiles BM, Lee BE, Rahouma M, Nasar A, Altorki NK, Port JL. Robotic Thymectomy Is Feasible for Large Thymomas: A Propensity-Matched Comparison. Ann Thorac Surg. 2017 Nov;104(5):1673-1678.
2. Kamel MK, Rahouma M, Stiles BM, Nasar A, Altorki NK, Port JL. Robotic Thymectomy: Learning Curve and Associated Perioperative Outcomes. J Laparoendosc Adv Surg Tech A. 2017 Jul;27(7):685-690.
3. Muaddi H, Hafid ME, Choi WJ, Lillie E, de Mestral C, Nathens A, Stukel TA, Karanicolas PJ. Clinical Outcomes of Robotic Surgery Compared to Conventional Surgical Approaches (Laparoscopic or Open): A Systematic Overview of Reviews. Ann Surg. 2021 Mar 1;273(3):467-473
4. Xu JX, Qian K, Deng Y, Zheng YY, Ou CM, Liu J, Jiang LH. Complications of robot-assisted thymectomy: A single-arm meta-analysis and systematic review. Int J Med Robot. 2021 Dec;17(6):e2333.

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