Asian Cardiovasc Thorac Ann 2003;11:72-73
© 2003 Asia Publishing EXchange Ltd
Posterior Mediastinal Schwannoma
Nicola Fierro, MD,
Guiseppe D’ermo, MD,
Giuseppe Di Cola, MD,
Luca Salvatore Gallinaro, MD,
Giorgio Galassi, MD,
Giovanni Galassi, MD
Department of Surgical Sciences and Applied Medical Technologies, University of Rome, La Sapienza, Rome, Italy
For reprint information contact: Nicola Fierro, MD Tel: 39 06 3089 2743 Fax: 39 06 3043 9368 email: n.fierro{at}tiscali.it Via Cassia, Rome 1710-00123, Italy.
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ABSTRACT
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An exceptional case of neurilemmoma in a 33-year-old asymptomatic man is described. Complete excision of an encapsulated 7.2-cm mass was achieved successfully. Pathological findings were consistent with a diagnosis of schwannoma with areas of sclerosis.
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INTRODUCTION
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Tumors arising from nervous structures, together with lymphomas and mediastinal cysts, are the most common mediastinal neoplasms. In children, they are usually malignant and tend to metastasize very early, while in adults, they are frequently benign and asymptomatic. They are most often found incidentally during routine chest radiography, and the differential diagnosis is generally difficult.
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CASE REPORT
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A 33-year-old man presented with widening of the mediastinal profile on a routine chest radiograph. Computed tomography of the neck and thorax revealed an abnormal mass with regular margins and a diameter of 3 cm, in the right posterosuperior mediastinum, localized posterior to the epiaortic vessels. The mass contained several large areas of calcification and descended down to the right bronchus, compressing the right lateral wall of the trachea (Figure 1
). Routine laboratory investigations were normal, but a moderate ventilatory difficulty was present. Magnetic resonance imaging indicated no intraspinal invasion of the tumor. Surgery was performed through a right posterolateral thoracotomy (4th space). Complete excision of a well-encapsulated mass measuring 7.2 cm at its widest diameter, was achieved. The excised mass appeared nodular with encapsulated whitish material containing 2 calcified cystic formations. Pathology showed fused cellular elements with eosinophilic cytoplasm and elongate nucleus, grouped into intertwined bands. These cellular elements were surrounded by abundant myxoid stroma and dense hypocellular connective tissue. Vascular ectasia, hemorrhagic effusion, and calcified areas were noted. Immunohistochemical analysis was positive for S-100 protein. These findings were consistent with a diagnosis of schwannoma with areas of sclerosis.
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Figure 1. Computed tomography of the thorax showing a mediastinal neoplasm (arrowed), approximately 3 cm in diameter, with calcifications.
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DISCUSSION
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Schwannomas usually arise in the base of the spinal nerves, but sometimes involve the thoracic nerves. They are often isolated lesions, however, multiple lesions along a nerve have been described. They may occasionally be associated with bone, skin, and central nervous system lesions (Von Recklinghausen’s neurofibromatosis).1 A solitary neurofibroma rarely tends to be malignant, but in patients with Von Recklinghausen’s disease, 4% to 10% of the tumors become malignant.2 Schwannomas of the mediastinum are usually benign, well-encapsulated, and consist of Schwann cells embedded in reticular tissue without nerve or collagen fibrils.3 They tend to be heterogeneous, particularly the large lesions, and have areas of cystic degeneration, low cellularity and necrosis, and small calcifications. Macroscopically, they present as lobular spheroidal masses.
Tumors have been diagnosed both in males and females, with a higher incidence in middle-aged or elderly patients.4 Most patients are asymptomatic, although a small percentage experience pain due to compression of the adjacent structures or intraspinal invasion of the tumor.4 Relapse is very rare. Radiologically, schwannomas appear as spherical paraspinal masses with clean lobular margins, involve one or two posterior intercostal spaces, and can grow to large dimensions.2 In 50% of cases, they cause benign erosions and deformities of the ribs, vertebral bodies, and nerve foramina. Routine chest radiographs rarely show calcifications.6 Computed tomography sometimes shows dots of calcification and areas of hypodensity corresponding to the zones of hypocellularity, which are cystic and hemorrhagic and filled with myelin lipids. After contrast medium infusion, schwannomas can appear homogeneous, heterogeneous, or with peripheral enhancement.6 Ten percent of schwannomas grow across the adjacent intervertebral foremen and extend across the spinal column in an hourglass or dumbbell shape. Magnetic resonance imaging shows medium to low T1-signal intensity and medium to high T2-signal frequency.
Magnetic resonance imaging is mandatory in all patients suspected of having a neurogenic tumor, to investigate intraspinal extension of the tumor.6 Radical surgical excision of the mass by thoracoscopy or thoracotomy is the treatment of choice. However, there is no way to determine the malignancy of the lesion; even benign tumors can grow to large dimensions and cause compression symptoms.7 Fine-needle aspiration or biopsy can be performed but accurate diagnosis may not be possible because of the limited cellularity of these neoplasms. A tumor showing intraspinal extension requires both a neurosurgical and thoracic approach.8 When possible, thoracoscopic excision is performed increasingly for neurogenic tumors of the posterior mediastinum, although this technique needs to be standardized, as evidenced by the reported high rate of conversion for technical reasons.8
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REFERENCES
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ABSTRACT
INTRODUCTION
