Ann Thorac Surg 2004;77:1088-1090
© 2004 The Society of Thoracic Surgeons
Case report
A case of thymoma protruding into the superior vena cava through the thymic vein
Yasuji Terada, MDa*,
Nobuhiro Ono, MDa,
Tetsuo Noguchi, MDb,
Kunihiko Kamakari, MDb,
Mitsuru Kitano, MDc
a Departments of Thoracic Surgery, Nagahama City Hospital, Nagahama, Japan
b Pulmonology, Nagahama City Hospital, Nagahama, Japan
c Cardiovascular Surgery, Nagahama City Hospital, Nagahama, Japan
Accepted for publication April 25, 2003.
* Address reprint requests to Dr Terada, Department of Thoracic Surgery, Nagahama City Hospital, Oinui-cho 313, Nagahama 526-8580, Japan.
e-mail: yaterada{at}ex.biwa.ne.jp
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Abstract
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We describe an unusual case of an invasive thymoma protruding into the superior vena cava and left brachiocephalic vein through the thymic veins in a 64-year-old patient. The tumor was resected with a bypass of the right brachiocephalic vein and right atrium. Although this type of growth form is rare for an invasive thymoma, this case suggests that in surgical procedures for thymomas, meticulous examination of the thymic veins is necessary to avoid leaving residual tumor.
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Introduction
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Thymoma is the most common tumor occurring in the anterior mediastinum, and its malignancy is defined by surgical evidence of invasion or the presence of intrathoracic or extrathoracic metastasis [1]. We present an unusual case of an invasive thymoma protruding into the superior vena cava (SVC) and left brachiocephalic vein through the thymic veins. The tumor was resected with a bypass of the right brachiocephalic vein and right atrium.
A 64-year-old patient presented at another hospital with anterior chest discomfort. A chest roentgenogram examination showed slight cardiomegaly (Fig 1), and chest computed tomography (CT) revealed an anterior mediastinal mass with pericardial effusion and filling defects in the SVC and left brachiocephalic vein (Fig 2). The mediastinal tumor did not appear to have any physical connection with the masses in the SVC and left brachiocephalic vein on CT, and therefore metastasis of the tumor was considered. A diagnosis of thymoma was made by CT-guided needle biopsy, but there were no symptoms of myasthenia gravis, and the serum level of antiacetylcholine receptor antibody was within the normal range. The patient underwent the surgical procedure on June 18, 2002, without any preoperative treatment because of the risk that the tumors in the large vessels would become detached from the vascular wall, causing pulmonary embolism. The mediastinal tumor was resected with the invaded parts of the pericardium and the infiltrated part of the right upper lobe of the lung. The roots of the intravascular masses were then recognized in the right and left thymic veins. After temporary external shunting for the right brachiocephalic vein to the right atrium, the intravascular masses were resected with minimum vessel wall resection of the SVC and the left brachiocephalic vein at the thymic veins. The tumors were seen to protrude from the thymic veins, and there was no direct invasion to the wall of the SVC and the brachiocephalic vein. The tumor was resected with clear margins, and the vessel wall was repaired with 5-0 Prolene sutures (Ethicon Inc, Somerville, NJ). The main tumor measured 7.5 x 6.5 cm, the tumor in the SVC measured 20 x 20 mm (Fig 3), and the tumor in the left brachiocephalic vein measured 10 x 7 mm. Histopathologic examination demonstrated a type B2 thymoma (Fig 4). No invading tumor cells were found in the wall of the SVC or the left brachiocephalic vein. After the operation, two cycles of adjuvant chemotherapy (50 mg/m2 cisplatin and 40 mg/m2 doxorubicin on day 1, 0.5 mg/m2 vincristine and 500 mg/m2 cyclophosphamide on day 3) and followed radiotherapy (60 Gy) were performed, and no recurrence has been recognized for 10 months postoperatively.
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Fig 2. Chest computed tomography demonstrates filling defects (arrows) in the superior vena cava and right brachiocephalic vein (Top) and an anterior mediastinal tumor with pericardial effusion (Bottom).
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Fig 3. The resected tumor in the superior vena cava was covered with fibrous tissue, and the root in the thymic vein (arrow) was recognized.
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Fig 4. Histopathologic appearance of the resected tumor, showing a type B2 thymoma with a predominance of epithelial cells but clearly visible lymphocytes (hematoxylin & eosin, original x400).
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Comment
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Invasive thymomas usually infiltrate adjacent organs in the mediastinal pleura, including the lungs, pericardium, great vessels, and heart, and extrathoracic metastases are very uncommon, occurring in only about 5% of cases [2]. Complications of malignant thymomas are usually the result of the local invasion of adjacent organs or are secondary to the development of myasthenia gravis [2]; cardiac tamponade and SVC syndrome are rare [3]. In the present case, the tumor in the SVC almost completely occluded the intravascular space, but there were no symptoms of SVC syndrome. The optimal treatment for invasive thymomas is complete resection, and therefore vascular wall reconstruction is necessary in invasive cases. Reconstructions of the SVC using the pericardium, the saphenous vein, a spiral vein graft [4], and expanded polytetrafluoroethylene (ePTFE) graft replacement or patch angioplasty [5] have been reported. For fibrosing mediastinitis, the use of ringed ePTFE grafts has been recommended to avoid later compression of the conduits [6, 7].
In this case of an invasive thymoma, the tumor protruded into the intravascular space through the thymic veins without direct invasion of the SVC wall. This is a particularly rare growth form for an invasive thymoma. Therefore, in cases in which a tumor in the SVC is associated with a mediastinal tumor, the possibility of an invasive thymoma protruding through the thymic veins should be considered. In addition, during the surgical procedure, a detailed examination of the thymic veins should be done to ensure that there are no residual tumors.
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References
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