Ann Thorac Surg 2005;79:1413-1415
© 2005 The Society of Thoracic Surgeons
Case report
A Rare Inferior Middle Mediastinal Tumor Resection Under Extra-Corporeal Circulation
Mehrdad Arab, MDa,
Claire Danel, MDb,
Nicola d'Attellis, MDc,
Karine Juvin, MDd,
Anne Hernigou, MDe,
Jean Noel Fabiani, MDf,
Marc Riquet, MD, PhD*,a
a Thoracic Surgery, Paris, France
b Pathology, Paris, France
c Anesthesia and Critical Care, Paris, France
d Pulmonary Medicine, Paris, France
e Radiology, Paris, France
f Cardiovascular Surgery, Hôpital Européen Georges Pompidou, Paris, France
Accepted for publication October 2, 2003.
* Address reprint requests to Dr Riquet, Service de Chirurgie Thoracique, Hôpital Européen Georges Pompidou, 20 Rue Leblanc, Paris 75015, France
marc.riquet{at}hop.egp.ap-hop-paris.fr
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Abstract
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An inferior middle mediastinal mass was observed in a 51-year-old woman initially presenting as pericardial effusion and mimicking lymph node disease. Thoracotomy demonstrated a tumor invading the posterior atrial wall. Complete resection was possible under the extracorporeal circulation. The tumor proved to be a soft tissue myoepithelioma in an exceptional location. Despite the difficult surgical resection due to location, prognosis of this absolutely rare tumor without cytologic features of malignancy should be good.
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Introduction
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Tumors of the middle and posterior mediastinum comprise approximately 50% of all mediastinal masses [1]. Common mediastinal masses observed in the middle mediastinum are lymphomas, bronchogenic cysts, and pericardial cysts [2]. Mesenchymal tumors may also be observed in any compartment and represent less than 10% of mediastinal tumors [3]. Nevertheless, they are particularly infrequent in the middle mediastinum. Diagnosis of the lesions located in this anatomically crowded region require further investigations because many may be treated by surgery. Sometimes, the presence of adjacent vital organs makes surgical resection limited. We report the successful removal of a very rare tumor located in the inferior middle mediastinum presenting with left atrial invasion.
A 51-year-old female patient who was a heavy smoker was referred to our department for diagnosis of a tumoral mass located within the inferior middle mediastinum. Symptoms appeared 1 year earlier and consisted of exertional dyspnea, and palpitation complicated by hypotension and fatigue. Echocardiography showed moderate pericardial effusion and a hypokinetic septum. Fiberoptic bronchoscopy demonstrated widening of the carina due to extrinsic compression. Thoracic computed tomographic scan revealed a hypo-dense retrocardiac mass (7 x 5 cm) beneath the carina. Furthermore, a left hilar adenopathy was observed with a pericardial nodule (Fig 1A). Tuberculosis was suggested, but further investigations for tuberculosis were negative. The diagnosis of another lymph node disease was suggested and because of the location, other diagnoses (bronchogenic cyst, lymphangioma, and so forth) had to also be considered. A transesophageal echocardiography was performed, which demonstrated a large heterogeneous mediastinal mass with probable left atrial invasion and lymph node involvement. A transesophageal-guided biopsy was not contributive. Because the mass presented with a pre-carinal development (Fig 1B,1C) mediastinoscopy was proposed. The pathology report of the lymph node biopsy was "nonnecrotizing granulomas compatible with sarcoidosis." All tests for sarcoidosis were negative; nevertheless, a trial therapy with corticosteroids was started. A computed tomographic scan performed 2 months later demonstrated no change in the mass; a surgical exploration was proposed to the patient, but she refused and corticotherapy was continued. The patient finally agreed to surgery 8 months after mediastinoscopy, because of progressive exertional dyspnea, and was referred to our department.
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Fig 1. (A) Heterogeneous retrocardiac mass located under the carina-pericardial nodule close to the coronary artery (arrow). (B) Beginning of the mass at the level of the carina. (C) Protrusion of the mass anteriorly from under the carina. (D) Left atrial compression by the mass.
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Surgery was performed through a right posterolateral mini-thoracotomy. The lesion was found to be a large mass located between the carina and right bronchus, posterior to the heart. A primary frozen section was initially negative for malignancy, and surgical dissection was attempted. Intrapericardial control of pulmonary veins and tumor dissection from the right pulmonary artery confirmed left atrial adhesion and extension to left-sided vessels. Repeated biopsies were suggestive of a malignant sarcoma-like tumor, and complete resection was not possible without risk; therefore, only the accessible portion of the right-sided tumor was resected. Pathology demonstrated lesions displaying epithelioid cells within a chondromyxoid matrix, which was in favor of a benign tumor mimicking a chordoma. Because of continuing dyspnea due to atrial compression (Fig 1D) the case was discussed with our cardiac surgical team, and it was decided to resect the tumor under extracorporeal circulation. The operative plan was to replace the "invaded" posterior aspect of the left atrium and if necessary, perform a left coronary bypass at the level of the intrapericardial nodule (Fig 1B).
Surgery was performed through a median sternotomy, and the tumor was approached through the pericardium. The left atrium was opened permitting resection of the mass under control with no need to replace the posterior atrial wall. The tumor was free from the esophagus, the vertebra, the carina, and the aorta without further difficulty. An extension of the tumor between the aorta and the pulmonary trunk was totally resected, as well as the extension along the left coronary artery without requiring revascularization. A pericardial patch at the level of the right pulmonary artery near the pulmonary trunk was also placed to repair a wound due to arterial wall fragility. The tumor appeared completely resected and the patient's postoperative stay was uneventful. The patient is doing well 7 months postoperatively. The definitive pathologic report was an invasive tumoral lesion with involvement of the left atrium muscle fibers. The tumor (Fig 2) demonstrates large areas of uniform-appearing epithelioid cells with clear or vacuolated cytoplasm, arranged in a nest or glandular pattern. These cells are embedded in a chondromyxoid matrix positively stained with periodic acid-Schiff's stain and Alcian blue. Immunohistochemistry was positive for cytokeratins AE1 to AE3 (Fig 3), CK7, vimentin, S-100 protein (Fig 4), calretinin, and carcinoembryonic antigen, but negative for actin, Ber-Ep4 and epithelial membrane antigen. These results suggest a chordoma, mucoepidermoid carcinoma, pericardial mesothelioma, or sarcomatoid, but as a whole these show fairly typical features of a mixed tumor, or a soft tissue myoepithelioma.
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Fig 2. Myoepithelioma and mixed tumor, monomorphic epithelioid myoepithelial cell arranged in nest within a myxoid stroma. (Hematoxylin & eosin, x200.)
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Comment
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Myoepithelioma is a rare tumor predominately or exclusively composed of myoepithelial cells. It is located more frequently in the salivary glands, but it has been reported in deep soft tissues, the breast, the larynx, the retroperitoneum, and the skin [4]. However, no reported case in the mediastinum could be found. Myoepitheliomas should be differentiated from various other tumors, among them chordomas [5], which was our primary diagnosis after the first operation. In fact, myoepitheliomas are known to mimic such lesions and are considered within a spectrum including "parachordoma" [6].
The location of the tumor, in the inferior mediastinum under the carina, initially led to a misdiagnosis toward a lymph node pathology (ie, tuberculosis, sarcoidosis, and lymphoma). Furthermore, the location of a myoepithelioma at this level raises the question of its origin. Original cells of these tumors have not been identified with precision but are considered to arise in the subcutaneous or deep subfascial soft tissues [6]. The present tumor may have originated from the atrial epicardium or myocardium, or in the posterior pericardium further expanding toward the left atrium wall.
Primary benign tumors represent about 90% of all cardiac tumors [7], 92% are myxomas, and only 6% of the remaining 8% are located within the left atrium [7]. Tumors originating from the pericardium are also rare and most often they are mesotheliomas. Localized malignant mesotheliomas need to be differentiated from other pericardial lesions [8] (ie, solitary fibrous tumors of the pericardium, epithelioid angiosarcomas, adenomatoid tumors, synovial sarcomas, and so forth). Localized mesotheliomas are capable of aggressive behavior; however, complete surgical excision may be curative [8]. Approximately 10% of soft tissue myoepitheliomas show obvious cytologic features of malignancy [6], but such features were absent in our patient. The presence of infiltrative margins and the difficult surgical excision due to location (requiring extracorporeal circulation and endocardiac surgical management) may well lead to future problems of local recurrence. Radiation therapy, the usefulness of which is not demonstrated in such rare tumors, was not believed to be advisable because of the cardiac location. On the other hand, the risk of metastasis from a tumor with this morphology remains small.
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Acknowledgments
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The authors thank Doctors Christopher D. M. Fletcher (Brigham and Women’s Hospital, Boston, MA) and Bryan Corrin (Brompton Hospital, London, UK) for their analysis and description of the histology.
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References
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Abstract
Introduction
