Ann Thorac Surg 2009;88:293-295. doi:10.1016/j.athoracsur.2008.11.070
© 2009 The Society of Thoracic Surgeons
Case Reports
Sclerosing Mediastinitis Mimicking Anterior Mediastinal Tumor
Toshio Miyata, MD,
Makoto Takahama, MD, PhD*,
Ryoji Yamamoto, MD, PhD,
Ryu Nakajima, MD, PhD,
Hirohito Tada, MD, PhD
Department of General Thoracic Surgery, Osaka City General Hospital, Osaka, Japan
Accepted for publication November 24, 2008.
* Address correspondence to Dr Takahama, Department of General Thoracic Surgery, Osaka City General Hospital, 2-13-22 Miyakojima hondori, Miyakojima-ku, Osaka, 534-0021, Japan (Email: mktkhm{at}yahoo.co.jp).
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Abstract
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A 54-year-old asymptomatic man presented with an anterior mediastinal mass discovered on chest roentgenogram. Chest computed tomography revealed a noncalcified round mass in the mediastinum. A white solid mass, 5-cm in diameter, had arisen from the pericardial adipose tissue with multiple small nodular lesions mimicking mediastinal tumor with pleural dissemination. Postoperative pathologic examination confirmed a diagnosis of sclerosing mediastinitis. Details of the clinical and radiographic feature are presented.
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Introduction
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Sclerosing mediastinitis is a rare condition characterized by proliferation of fibrous tissue within the mediastinum. Most cases occur idiopathically, with symptoms related to compression of the central airways, superior vena cava, pulmonary veins, pulmonary arteries, and esophagus. We report a rare case of asymptomatic sclerosing mediastinitis mimicking mediastinal tumor with pleural dissemination.
A 54-year-old asymptomatic man was referred to Osaka City General Hospital with an anterior mediastinal mass that had been discovered on chest roentgenogram. He displayed no symptoms related to the mass and had no history of serious illness. Laboratory studies showed no findings of inflammatory reaction.
A contrast-enhanced chest computed tomography (CT) scan revealed a 38- x 25-mm noncalcified mass located by the pericardium, but no disseminated nodular lesions (Fig 1). The mass was poorly enhanced by contrast media. The mass showed signal hypointensity on T1- and T2-weighted magnetic resonance imaging (MRI). This decreased signal intensity was thought to indicate the presence of fibrous tissue.
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Fig 1. Contrast-enhanced computed tomography scan reveals a 38- x 24-mm noncalcified mass in the anterior mediastinum. The mass is poorly enhanced by contrast medium.
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Because malignancies could not be excluded by these examinations, the patient underwent a video-assisted thoracoscopic procedure. A white solid mass, 5 cm in diameter, had arisen from the pericardial adipose tissue with multiple small nodular lesions. The mass was resected with the mediastinal adipose tissue, and part of the lung containing disseminated nodular lesions was resected (Fig 2). The multiple disseminated small nodules in the parietal pleura and diaphragm were left intact.
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Fig 2. (A) A white solid mass, 5 cm in diameter, arising from the pericardial adipose tissue. (B) Multiple small nodular lesions are apparent in the mediastinal adipose tissue. (C) The part of the lung showing small nodular lesions was resected.
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The histopathologic examination showed the lesion was mainly composed of dense fibrous tissue with infiltration of lymphocytes and plasma cells (Fig 3). No granulomatous or neoplastic lesions were evident, and methenamine silver staining for fungi yielded negative results. Results of tests for mesenchymal markers such as CD34 were negative. Sclerosing mediastinitis was diagnosed histologically. The resected disseminated lesion of the lung displayed the same histopathologic diagnosis. The patient's postoperative course was uneventful, and he was healthy at the 6-month follow-up.
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Fig 3. Histopathologic examination with hematoxylin-eosin stain revealed that the lesion mainly comprised dense fibrous tissue with infiltration of lymphocytes and plasma cells. No granulomatous or neoplastic lesions were present. (A) Original magnification x40. (B) Original magnification x400.
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Comment
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Sclerosing mediastinitis, which has also been termed fibrous mediastinitis, is a rare condition resulting in the deposition and proliferation of dense fibrous tissue. This inflammatory process can lead to compression of vital mediastinal structures such as the superior vena cava, esophagus, trachea, and pulmonary arteries and veins [1]. The causes of this disorder are thought to be Histoplasma capsulatum infection, tuberculosis, sarcoidosis, trauma, drugs, malignancies, and autoimmune disease [2]. The pathogenesis of extensive progressive fibrosis within the mediastinum remains unclear. Goodwin and colleagues [3] proposed the most favored hypothesis, that sclerosing mediastinitis results from a delayed hypersensitivity reaction to fungal, mycobacterial, or other unknown antigens. Although many cases in the United States are thought to result from an abnormal immunologic response to H capsulatum infection, the exact cause is unknown in most patients. Flieder and colleagues [4] recently proposed the term idiopathic fibroinflammatory lesion of the mediastinum.
Two types of sclerosing mediastinitis may be identified on CT: focal and diffuse. The focal type, seen in 82% of patients, usually manifests as a localized, frequently calcified (63% of patients) mass in the paratracheal or subcarinal regions of the mediastinum or in the pulmonary hila. The diffuse type manifests as a diffusely infiltrating, often noncalcified mass that affects multiple mediastinal compartments [5]. Because MRI depicts calcification poorly, CT is considered the mainstay for diagnostic evaluation of sclerosing mediastinitis.
Surgical investigation is necessary to achieve a definitive diagnosis in most cases, because the neoplasms that most frequently produce fibrosis, and thus must be included in the differential diagnosis, include sclerosing non-Hodgkin lymphoma and the nodular sclerosis variant of Hodgkin disease. Solitary fibrous tumors of the pleura should also be considered, although a spindle cell origin can be readily excluded by immunohistochemical staining for CD34. Biopsy samples obtained by percutaneous needle technique may be insufficient to rule out malignancy due to the limited size, so open biopsy with extensive sampling is frequently required to establish a definitive diagnosis [2, 6].
In most patients with sclerosing mediastinitis, resecting the fibrous tissue is not possible [1]. Use of antifungal agents or steroids is generally not useful in established cases with extensive fibrosis [7]. Most reports advocate minimal intervention unless symptoms become life-threatening [2]. Loyd and colleagues [1] reported a mortality rate exceeding 30%, with recurrent infection, hemoptysis, and cor pulmonale as typical causes of death. The mortality rate among patients with subcarinal or bilateral mediastinal involvement may be high [1].
In the present patient, sclerosing mediastinitis manifested as a localized round mass with multiple disseminated small nodules mimicking mediastinal tumor with pleural dissemination. CT and MRI could not show the small nodular lesions of the mediastinal adipose tissue and pleura, representing a rare pattern of sclerosing mediastinitis [8].
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Acknowledgments
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We thank Dr Ken Inoue of the Department of Pathology at Osaka City General Hospital for his kind assistance and advice on histopathologic diagnosis.
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References
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Abstract
Introduction
