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Three-dimensional computed tomography-guided excision of an intrathoracic giant thymoma with elongated thymic vessels
We report the case of an intrathoracic giant thymoma with elongated thymic vessels, which was successfully resected under three-dimensional computed tomography guidance. A large, left-sided intrathoracic mass was incidentally found in a 41-year-old woman during a routine work-up for uterine cancer. Six vessels were noted arising from the tumor, five of which were connected to the anterosuperior mediastinum. The vasculature suggested that the tumor originated from the thymus and grew into the left pleural cavity, which pulled and elongated the associated vessels. Preoperative computed tomography imaging demonstrated that these vessels were located behind the tumor, which increased the risk for catastrophic intraoperative bleeding. We created a detailed surgical plan using our preoperative computed tomography data and successfully excised the tumor using intraoperative three-dimensional computed tomography guidance. Histopathological examination revealed a type AB thymoma without capsular invasion. This case highlighted the role of preoperative planning and intraoperative imaging in resecting an intrathoracic giant thymoma safely. In the video, we demonstrate how we performed the procedure under three-dimensional navigation.
The differential diagnoses for an intrathoracic giant tumor include mesenchymal tumors, germ cell tumors, neurogenic tumors, lymphoma, and thymic epithelial tumors . Intrathoracic giant thymomas are rare and account for 4% of all intrathoracic giant tumors . Although several cases of intrathoracic giant thymomas have been reported , details on its vasculature and the appropriate surgical approach remain unclear. Herein, we report a case of an intrathoracic giant thymoma in which computed tomography (CT) played a central role in diagnosis and surgical treatment.
A large, left-sided intrathoracic mass was incidentally noted in a 41-year-old woman with uterine cancer who consulted for genital bleeding. The patient denied any chest pain or respiratory symptoms. The intrathoracic mass demonstrated a maximum standardized uptake value of 4.7 on 18-F fluorodeoxyglucose-positron emission tomography but showed no evidence of metastasis. Radiotherapy for clinical stage IIIB squamous cell uterine cancer was administered prior to surgical treatment of the intrathoracic mass. A follow-up CT showed no change in the size of the mass.
1 - Preoperative computed tomography findings (0:13)
Contrast-enhanced chest CT revealed a well-defined 12-cm mass adjacent to the mediastinum, diaphragm, and lungs. The mass occupied more than half of the left lower thoracic cavity.
2 - 3D CT imaging for preoperative planning (0:34)
3D-CT imaging demonstrated three feeding arteries from the superior thyroid, inferior phrenic, and internal thoracic arteries and three drainage veins from the inferior thyroid, proximal innominate, and distal innominate veins. We theorized that the tumor originated from the anterior mediastinum because the origins of the feeding and drainage vessels, with the exception of the inferior phrenic artery, were consistent with the origins of the thymic vessels .
We planned our intraoperative technique based on the preoperative 3D-CT findings. In particular, we noted that the above-mentioned vessels were located posteriorly; accessing them from a conventional thoracotomy incision was associated with an increased risk for injury and catastrophic bleeding during surgery. Based on our preoperative simulation, our surgical plan involved separating the feeding artery from the inferior phrenic artery located over the diaphragm; dissecting the caudal end of the tumor from the pericardium; dissecting the posterior portion of the tumor from the lungs; and dissecting the cephalad end of the tumor from the anterosuperior mediastinum with careful dissection of the vasculature.
For the surgical approach for this giant intrathoracic mass, we opted for a left anterolateral thoracotomy because the main tumor was located in the left pleural cavity, and the tumor was not attached to the sternum. In our institution, we opt for a median sternotomy if the main location of the tumor is the anterior mediastinum. We use a minimally invasive approach if the tumor is less than 5 cm.
3 - 3D CT imaging for intraoperative guidance (1:27)
A lateral 20-cm incision was made along the 5th intercostal space. The 6th rib was divided posteriorly. No pleural effusion or metastasis was observed. A large tumor was noted in the thoracic cavity, abutting the pericardium and left lung and diaphragm and demonstrating wide attachments to the mediastinum and lungs. Preoperatively, we theorized that the tumor arose from the mediastinum because of the vessels identified on imaging; however, intraoperatively, we noted that the tumor was attached to the lungs through adhesions.
Using 3D-CT guidance, we retracted the tumor in a cephalad direction to expose the feeding artery, which was positioned above the diaphragm. We ligated this artery and dissected it from the inferior phrenic artery. We then dissected the caudal end of the tumor from the pericardium. We retracted the tumor anteriorly to expose the adhesions between the posterior portion of the tumor and lungs, which we also dissected. The tumor was then retracted caudally to allow us to dissect the cephalad end of the tumor from the mediastinum. We ligated the feeding and drainage vessels to fully separate the tumor from its bed. In particular, the feeding artery that originated from the internal thoracic artery was ligated and dissected. Behind this artery, we identified and ligated a vein that drained into the inferior thyroid vein. In the following order, we also identified and ligated a vein that drained into the distal innominate vein, a feeding artery that originated from the superior thyroid artery, and a vein that drained into the proximal innominate vein. The tumor was excised successfully.
Outcome
Histopathological examination of the surgical specimen revealed a type AB thymoma without capsular invasion (Masaoka stage I). The patient’s postoperative course was uneventful, and the patient remained disease-free at the 1-year follow-up.
Discussion
This case highlighted the role of preoperative surgical planning and intraoperative navigation using 3D-CT imaging to achieve a safe and secure resection of an intrathoracic giant thymoma. In particular, our 3D-CT data allowed us to create a detailed surgical plan designed to minimize intraoperative injury to the elongated vessels visualized behind the tumor.
In healthy individuals, the arterial supply to the thymus arises mainly from the internal thoracic, pericardiacophrenic, brachiocephalic, and inferior and superior thyroid arteries. The pericardiacophrenic artery is a branch of the internal thoracic artery and accompanies the phrenic nerve. In contrast, the venous drainage of the thymus occurs chiefly through the innominate, internal thoracic, and inferior thyroid veins . In patients with a thymoma, these thymic vessels become the feeding arteries and drainage veins of the tumor. In the present case, two feeding arteries and three drainage veins were observed arising from the anterosuperior mediastinum, which suggested that these vessels had thymic origins. Moreover, the presence of these vessels indicated that the tumor arose from the thymus but shifted into the left pleural cavity, with concomitant elongation of the identified vessels.
Although more than 90% of thymomas are located in the anterosuperior mediastinum , they may occasionally present as intrathoracic giant tumors. Intrathoracic giant thymomas are usually excised through a thoracotomy incision instead of a median sternotomy incision because of their location . However, previous case reports that documented intrathoracic giant thymomas did not describe the vasculature of these tumors. We speculated that the majority of intrathoracic giant thymomas have elongated thymic vessels that originate from the anterosuperior mediastinum, as was observed in our case. However, thymomas may also arise from ectopic thymic tissue in the pleural cavity.
Preoperative simulation and intraoperative navigation using 3D CT images are useful, especially when the surgical vision is limited. Therefore, the usefulness of 3D CT imaging during minimally invasive surgery has been widely accepted. Furthermore, 3D CT imaging-based simulation/navigation is useful in various thoracotomy cases, including our present case. We successfully identified and divided elongated feeding arteries and drainage veins in this patient. To remove the tumor safely, we planned to dissect the caudal and posterior ends of the tumor, followed by the cephalad portion, which was where the elongated vessels were located. We prioritized the caudal and posterior portions of the tumor to maximize the dissection of the surrounding tissues, because we considered that there was a high risk for uncontrollable and catastrophic bleeding from the elongated thymic vessels if we dissected them blindly without prior dissection of the surrounding tissues. In addition, we wanted to have a wide surgical field for hemostasis if we injured the above-mentioned vasculature. Overall, 3D-CT imaging contributed to preoperative planning and helped us identify the main vessels during surgery.
We previously reported the role of 3D-CT reconstruction in pulmonary segmentectomy . In our institute, each surgeon is assigned a personal monitor for 3D-CT visualization during intrathoracic navigation. Working with the monitor allows the surgeon to compare the intraoperative anatomy with the 3D-CT images in real time and confidently and safely perform the operation.
In conclusion, preoperative surgical planning is crucial for intrathoracic giant thymomas, because the location and vascular anatomy of these tumors are complex. 3D-CT imaging effectively demonstrated the relationship between this tumor and its vessels and aided in preoperative planning and intraoperative navigation.
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PubMed Abstract | ICVTS Full Text - Saito T, Makino T, Hata Y, Koezula S, Otsuka H, Isobe K et al. Giant thymoma successfully resected via anterolateral thoracotomy: a case report. J Cardiothorac Surg 2015;10:110.
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PubMed Abstract | EJCTS Full Text
We would like to thank Editage (www.editage.com) for English language editing.
None declared.
Authors
Shunichiro Matsuoka, Takashi Eguchi, Tsutomu Koyama, Tetsu Takeda, Kentaro Miura, Kazutoshi Hamanaka, and Kimihiro Shimizu
Authors' Affiliation
Division of General Thoracic Surgery, Department of Surgery, Shinshu University School of Medicine, Matsumoto, Japan
Corresponding Author
Takashi Eguchi
Division of General Thoracic Surgery, Department of Surgery, Shinshu University School of Medicine, Matsumoto, Japan
Phone: +81-263-37-3576
Email: eguchi_t@shinshu-u.ac.jp
Keywords
© The Author 2021. Published by MMCTS on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
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