Ann Thorac Surg 2000;69:280-281
© 2000 The Society of Thoracic Surgeons
Case Reports
Primary tracheal schwannoma
Julia Dorfman, MDa,b,
Bruce M. Jamison, MDa,b,
Jean E. Morin, MDa,b
a Department of Surgery, Cardiothoracic Surgery Service, McGill University, Montreal, Quebec, Canada
b Department of Pathology, Cardiothoracic Surgery Service, McGill University, Montreal, Quebec, Canada
Address reprint requests to Dr Morin, Royal Victoria Hospital, 687 Pine Ave W, Suite S8.30, Montreal, PQ, Canada, H3A 1A1
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Abstract
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We report a case of a primary tracheal schwannoma causing symptoms of airway obstruction in a 33-year-old man. Bronchoscopy and computerized tomography demonstrated a polypoid intratracheal mass obstructing 90% of the lumen. Tracheal resection with primary anastomosis was performed. Histologic analysis revealed a benign neurogenic tumor of Schwann cell origin.
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Introduction
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Primary tracheal tumors are rare. The majority of tracheal tumors are malignant and most of these lesions are of two histologic types: squamous cell carcinoma or adenoid cystic carcinoma [1]. Benign tracheal tumors are much less frequently encountered and comprise a widely heterogeneous group [1]. We report a case of a primary tracheal schwannoma, an exceedingly rare lesion.
A 33-year-old man with a 20 pack/year smoking history complained of difficulty breathing, on exertion and at rest, for a period of 6 months. Treatment with bronchodilators did not alleviate symptoms. Expiratory wheezes could be heard throughout both lung fields. In addition, wheezing was present during auscultation over the trachea. The remainder of the physical examination was normal. The chest roentgenogram was within normal limits. Pulmonary function studies demonstrated a moderate obstructive ventilatory defect with no significant bronchodilator response. The flow-volume loop was suggestive of a fixed upper airway obstruction because of flattening of both the inspiratory and expiratory curves. Flexible bronchoscopy revealed an endotracheal mass, located 8 cm distal to the vocal cords, which appeared to be occupying almost the entire lumen of the trachea. Because of the obstructing nature of the mass, an attempt was not made to advance the bronchoscope past the lesion. The lesion was not biopsied to avoid bleeding and further obstruction. Computed tomography was performed to delineate the distal extension of the mass. It demonstrated a polypoid intratracheal lesion occluding approximately 90% of the lumen and occupying a 2 cm length of trachea (Fig 1). There was no mediastinal extension or adenopathy.
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Fig 1. Contrast-enhanced computed tomogram of the chest. An intratracheal polypoid mass is seen obstructing 90% of the lumen.
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A 2.5 cm segment of trachea was resected and primary anastomosis was performed. The initial approach was a transverse cervical incision, but an upper sternal split was then added due to inadequate exposure with the former. Frozen section suggested a benign neoplasm, but a specific tissue diagnosis was not available. The resection margins were free of tumor. No release maneuvers were performed. Pulmonary function studies were repeated during the second postoperative week and showed that measured lung volumes were 90% of predicted values. Flow-volume loops were also normal at this time. Pulmonary function testing was also normal at the third postoperative month.
The specimen of resected trachea contained a 2.2 cm diameter and 1.2-cm-long spherical, pedunculated mass arising from the membranous portion of the trachea (Fig 2). Microscopic evaluation of the lesion demonstrated a nonencapsulated and focally invasive spindle cell tumor composed of bland cells arranged in either a storiform or interlacing fascicular pattern (Fig 3). Areas of atypical nuclei and increased cellularity were present; however, these areas showed little, if any, mitotic activity. Vague nuclear "palisading" was observed in some areas. Focal areas of necrosis and heightened vascularity were observed in the center of the lesion. The periphery of the tumor, where it met the trachea, revealed insinuation of tumor bundles between smooth muscle fibers of the tracheal submucosa.
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Fig 2. Tracheal mass in situ. The trachea has been transected distal to the lesion (endotracheal tube is within the distal trachea). The mass can be seen within the proximal tracheal segment.
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Fig 3. Microscopic examination of tumor showing features of a benign cellular schwannoma (see text for details) (Hematoxylin and eosin stain, magnification x10).
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Immunohistochemical stains revealed strong uniform positivity for S-100 protein and vimentin throughout the entire lesion. Synaptophysin was focally positive in nerve fiberlike areas. Stains for muscle-specific actin, desmin, and cytokeratin were negative. The histologic features are consistent with a tumor of Schwann cell lineage. In spite of focal evidence of infiltration (with entrapment of muscle cells), hypercellularity, and nuclear atypia, a diagnosis of benign cellular neurilemmoma (cellular schwannoma) is favored. This is supported by the strong expression of S-100 protein, because a malignant tumor is likely to show only focal or minimal expression of this protein. Furthermore, no substantial mitotic activity or tumor necrosis was observed. Results of electron microscopic analysis supported the diagnosis of schwannoma.
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Comment
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Primary tracheal tumors are less frequently observed than bronchial tumors. Even though published series of tracheal tumors span many years, they contain relatively small numbers of patients. Two thirds of all primary tracheal tumors are almost evenly divided between squamous cell carcinoma and adenoid cystic carcinoma [1]. The remaining third is a heterogeneous group composed of malignant, intermediate, and benign lesions [1].
Primary neurogenic tumors of the trachea (schwannomas or neurilemmomas) are extremely uncommon. As with other intraluminal tumors, symptoms of airway obstruction predominate. Diagnosis is usually made endoscopically, but computerized tomography and magnetic resonance imaging are increasingly used to delineate tumor size, location, and extension [2]. The standard management of tracheal tumors is circumferential resection with tracheal reconstruction. Endoscopic laser resection also has been used successfully in the management of benign tracheal tumors [3]. Schwannomas are typically circumscribed and encapsulated tumors. Microscopically, they have regions of high and low cellularity, called Antoni A and B areas, respectively [4, 5]. Foci of palisaded nuclei, called Verocay bodies, may be present in the Antoni A tissue [5]. A tracheal tumor should be considered in the differential diagnosis of patients with obstructive airway symptoms, especially if unresponsive to conventional therapy.
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References
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Grillo H.C., Mathisen D.J. Primary tracheal tumors. Ann Thorac Surg 1990;49:69-77.[Abstract]
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Ikezoe J., Sone S., Higashihara T., et al. Schwannoma of the trachea. Eur J Radiol 1986;6:65-66.[Medline]
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Rusch V.W., Schmidt R.A. Tracheal schwannoma. Thorax 1994;49:85-86.[Abstract/Free Full Text]
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Nass R.L., Cohen N.L. Neurilemmoma of the trachea. Arch Otolaryngol 1979;105:220-221.[Abstract/Free Full Text]
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Inoue H., Tsuneyoshi M., Enjoji M., Ishida T., Yasumoto K., Sugimachi K. Endotracheal neurilemmoma with a lymphoid cuff. An ultrastructural and immunohistochemical study. Acta Pathol Jpn 1989;39:407-412.[Medline]
Accepted for publication June 1, 1999.
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Abstract
Introduction
