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Tex Heart Inst J. 2004; 31(3): 309 --312.

Large Mediastinal Teratoma Originating from the Aortic Adventitia
Ufuk Yetkin, MD, Aylin Orgencalli, MD, Gokhan Yuncu, MD, and Ali Gurbuz, MD

Izmir Ataturk Education and Research Hospital, Department of Cardiovascular Surgery, Izmir, Turkey

Address for reprints: Ufuk Yetkin, MD, 1379 Sok. No: 9, Burc Apt. D:13, 35220 Alsancak -- Izmir, Turkey

 Abstract 
 

Many mediastinal tumors do not cause local symptoms, so they are discovered incidentally upon thoracic imaging. We present the case of a patient who had a large, mature, cystic, mediastinal teratoma. The primary tumor arose from the ascending aortic adventitia and was in a highly unusual location ---the medial mediastinum. The teratoma, which was diagnosed in our patient on thoracic computed tomography for follow-up evaluation of empyema, was resected completely. To our knowledge, such a teratoma, arising from the adventitia of the ascending aorta in the medial mediastinum, has not previously been reported in the English medical literature.

We review diagnostic methods and therapeutic approaches to such mediastinal tumors. We conclude that surgical resection is the method of choice for treating these tumors, because it enables radical therapy and tissue diagnosis after extirpation.

Keywords: Magnetic resonance imaging, mediastinal cyst, mediastinal neoplasms/diagnosis/surgery, radiography, thoracic, surgical resection, teratoma/diagnosis/surgery, tomography, X-ray computed, tumor markers, biological/blood/diagnostic use
 Introduction 
 

Many different tumors and cysts can arise from mediastinal anatomic structures.1 Most of these primary mediastinal masses are diagnosed incidentally during routine chest radiography.2,3 Early diagnosis and therapy is rare, because mediastinal masses are generally diagnosed only after they begin to compress the adjacent structures. At that point, these masses can become malignant, and surgery provides the only chance for a cure.3,4 We report the case of a patient who had a large, mature, cystic teratoma of the medial mediastinum that arose from the ascending aortic adventitia. We present our diagnostic methods and our techniques for successful resection of the teratoma.

 
 Case Report 
 

In March 2003, a 19-year-old man was referred to our clinic after a mediastinal cystic lesion was found on a routine, follow-up, thoracic computed tomographic (CT) scan. Six months before admission to our clinic, the patient had undergone an appendectomy and retroperitoneal abscess drainage at another institution. He had then been hospitalized elsewhere on the 17th postoperative day, and was given medical therapy for right pleural empyema (Fig. 1). When he was discharged, he was advised to return for a 3-month follow-up thoracic CT scan. It was this CT scan that revealed the lesion and led to a consultation at our clinic.

The thoracic CT scan showed a mediastinal, cystic lesion, 8 cm in diameter, with smooth borders. The mass extended from the upper mediastinal area, in front of the aorta and pulmonary artery, to the right atrium (Fig. 2). The CT scan was examined for mediastinal cystic lesions such as pericardial or hydatid cysts. Echocardiography showed a paracardiac mass compressing the right ventricular base, the right atrium, and the aorta (the aortic root and ascending aorta). The mass surrounded the proximal part of the ascending aorta. It was encapsulated and contained homogenous granular tissues. We did not see any flow within the mass, and there was no agitated fluid passing to the mass from the heart; therefore, we determined this to be a paracardiac mass compressing the right atrium. On a thoracic magnetic resonance image (MRI), we found a smooth, contoured, cystic lesion beginning in the right ventricle and extending to the right atrium, invading the anterior mediastinum; its dimensions were 8.5 x 6.5 cm. The lesion occupied a large portion of the anterior mediastinum and displaced the main vascular structures and the heart to the left. No disease was evident on complete abdominal ultrasonography, computed brain tomography, or whole-body bone scintigraphy. Thyroid scintigraphic results were normal, as were the levels of serum [alpha]-fetoprotein, human chorionic gonadotropin-[beta] subunit ([beta]-HCG), and other tumor markers. The patient underwent surgery for removal of the cystic mass.


 Surgical Technique 
 

At surgery, with the patient under general anesthesia, the right femoral artery and vein were prepared in case a perioperative complication necessitated emergency cardiopulmonary bypass. Upon pericardial incision, we found a 10- x 10-cm intrapericardial mass that was adherent to the ascending aorta and the pulmonary artery by its pedicle. The mass was resected from the pedicle. We found that the mass arose from the ascending aorta's inner curvature and was adherent to the pulmonary artery. A collateral of the nutritional artery was transected, and the aortic wall, which was injured during the transection, was repaired with continuous Prolene suture and Teflon pledgets. Then the entire mass was resected. Further exploration showed that the mass had not invaded any other region.

The cyst was filled with brown, gelatinous, homogenous, hyperviscous fluid. On histopathologic evaluation, the tumor was diagnosed as a benign, mature, cystic teratoma with scattered mucoid material in its tunica mucosa (Figs. 3 and 4).

The patient was discharged from the hospital 6 days after the operation. Follow-up at an internal oncology and cardiovascular surgery outpatient clinic has shown him to be free of disease.


 Discussion 
 

Most mediastinal teratomas are benign.2,4,5 Although they are seen in patients of all ages, they are most common in young adults. Teratomas consist of 3 germ layers, of which the ectodermal component is dominant.6 Histopathologic evaluation of the tumor in our case showed dominance of the ectodermal structures (Figs. 3 and 4).

Most mediastinal tumors do not cause local symptoms; in adults, two thirds of cases are asymptomatic.4,7 Therefore, these tumors tend to be diagnosed incidentally by thoracic imaging, as was the case with our patient. When symptoms occur, they can be due to compression, invasion of the adjacent intrathorac-ic structures, or various co-syndromes.4,8 Despite the relatively large size of cystic teratomas, compression symptoms are rare, due to the cystic structure.7 The most frequent symptom is chest pain.6

Teratomas are the 2nd-most-frequent tumors of the anterior mediastinum, after thymomas.9 A mass found on thoracic imaging to have smooth contours and calcified areas in the anterior mediastinum is very likely a teratoma.9,10 Whatever its location, size, and shape, a teratoma or another mediastinal mass warrants thoracic CT scanning. The thoracic CT delineates the structural features and the extent of invasion to the adjacent tissues; the mass can be differentiated from vascular structures by use of contrast material.11 A mediastinal mass's homogeneity, density, contour, size, and exact location can also be determined in detail.12 The presence of bony elements on the thoracic CT scan confirms the diagnosis; however, they are not found in all instances.9 In recent years, thoracic MRI has been used to evalu-ate neurogenic tumors in the posterior mediastinum and masses suspected of invading vascular structures.13 This method helps to determine whether a mediastinal mass has invaded the thoracic wall,14 and provides other detailed information about such masses, as it did in our patient. Echocardiography is useful for evaluating the compression by the mediastinal mass to cardiac and major vascular components, as well as the mass's size, location, contents, and flow (both within the mass and from the heart to the mass).15

Serum [alpha]-fetoprotein and [beta]-HCG levels must be measured if a teratoma or similar germ-cell tumor is suspected. An abnormal level of one or both markers is diagnostic.6 If there is an anterior mediastinal mass, the possibility of substernal thyroid must be considered and thyroid scintigraphy with radioactive iodine performed.16

Cystic rupture can occur and is usually caused by infection.17 Rarely, a mediastinal tumor ruptures into the tracheobronchial system, and blood, hair, and gelatinous material can be expectorated.12,18 If the tumor has a connection with a bronchial passage, an air-fluid level is seen. If the tumor ruptures into a pleural or pericardial region, it can cause pleural empyema, acute respiratory distress, and pericardial tamponade.18 None of these events occurred in our patient.

Total surgical excision is indicated for any malignant or benign well-demarcated mass in any part of the mediastinum. The best approach for masses in front of the heart and great vessels is a median sternotomy.4,11 Surgery is necessary because compression will eventually affect the surrounding tissues; in addition, all benign tumors and cysts in the mediastinum can show malignant differentiation with time.19 The tendency toward malignancy extends to all teratomas and mediastinal tumoral or cystic neoplastic growths, and compression or hemorrhage is likely. Therefore, such tumors ---in particular those that have a cytologic or histologic benign diagnosis or are thought to be benign according to their clinical and radiological findings ---must be resected.1,2,6 Complete extirpation enables accurate diagnosis and therapy, as it did in our patient.

To our knowledge, another case of a teratoma arising from the adventitia of the ascending aorta in the medial mediastinum has not been reported in the English medical literature. In our patient, complete extirpation of the benign, mediastinal teratoma led to a successful result. We conclude that surgery is the treatment of choice, because it is best for radical therapy.


 References 
 
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 Figures and Tables 
 


Fig. 1 Posteroanterior radiograph used in the diagnosis of empyema.


Fig. 2 Thoracic computed tomographic scan of the mediastinal cystic lesion.


Fig. 3 Left: Ciliary cylindrical epithelium (a), mixed salivary gland (b), and cartilage (c) covering the cyst, seen on histopathologic section (H&E, orig.


Fig. 4 Left: Image of brain tissue (from the teratoma) containing cartilage (a) and psammoma bodies (b) at histopathologic section (H&E, orig.