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July - September 2007: 
Volume 20, Issue 3

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A case of two simultaneous thoracic schwannomas
Abstract
SUMMARY. The case is presented of a patient with two thoracic tumours. The diagnostic approach included the use of conventional chest X-ray, thoracic CT scan, 3D CT and an FNA core biopsy. The management was based on surgical excision of the tumours. The histological examination of the surgical tissue biopsy revealed two schwannomas and excluded malignancy. Pneumon 2007; 20(3):258-262
Full text

Introduction

Schwannomas are tumours of the peripheral nerves that originate in the nerve sheath (Schwann cells), and in adults 90% of cases are benign. Thoracic schwannomas are most frequently located in the posterior mediastinum. The presence of two simultaneous schwannomas derived from two contiguous intercostal nerves, as in the case reported here, is extremely rare.

The Case Report

A 62 year-old woman presented at the outpatient department complaining of left-sided chest pain, moderate in intensity, of six months duration. She had no history of smoking. Postero-anterior chest X-ray showed one coin-shaped lesion in the left hemithorax, adjacent to the seventh rib (Figure 1). The chest CT (Figures 2, 4, 6) revealed a 3x3cm tumour in the middle of the seventh rib with endothoracic protrusion. CT guided fine needle aspirate (FNA) (core biopsy) demonstrated fibrosis. A second radiographic approach, 3 months later, with a 3D chest CT scan showed a second tumour 1cm in diameter, located in the left paravertebral space (Figures 3, 5, 7). On surgery, resection of the tumours was effected through a left postero-lateral thoracotomy, without damaging the anterior serratus muscle. The surgical tissue biopsy excluded malignancy, and the histological examination revealed the picture of benign schwannoma in both tumours (Figures 8a, 8b): “The lesion is comprised of short cellular fascicles alternating with less cellular areas arranged haphazardly in the loosely textured matrix. Both components display mild to moderate nuclear atypia of a degenerative nature in an old schwannoma”.

Figure 1. Chest X-ray showing a nodule next to the left seventh rib.
Figure 2. Conventional chest CT scan (transverse plane) showing a schwannoma with endothoracic protrusion located in the middle of the left seventh rib.
Figure 3. 3D chest CT scan (transverse plane) showing a schwannoma with endothoracic protrusion located in the middle of the left seventh rib.
Figure 4. Conventional chest CT scan (transverse plane) showing a left paravertebral schwannoma.


Discussion

Neurogenic tumours are commonly found in the mediastinum, especially in the posterior mediastinum or in the chest wall. In adults most of these tumours are malignant (87-96%). Early surgical excision is considered to be the most acceptable strategy, because of the uncertainty of the preoperative diagnosis, the increasing size of the tumour, the possibility of malignancy and/or the need for alleviation of symptoms1. The majority of patients with posterior mediastinal neurogenic tumours are asymptomatic, and the lesions are discovered incidentally on chest X-ray2. Chest CT and MRI are useful in the diagnosis of early spinal cord involvement, which is present in 10% of these patients. As the tumours become larger in size, they can produce symptoms related to local compression or bone erosion3.

Figure 5. 3D chest CT scan (transverse plane) showing a left paravertebral schwannoma.
Figure 6. Conventional chest CT scan (coronal plane) showing both the schwannoma located in the middle of the left seventh rib and the left paravertebral schwannoma.
Figure 7. 3D chest CT scan (coronal plane) showing both the schwannoma located in the middle of the left seventh rib and the left paravertebral schwannoma.



65% of mediastinal neurogenic tumours arise from the nerve sheath and 35% from nerve cells4. Benign tumours of the nerve sheath include neurilemmomas or schwannomas (most frequent) and neurofibromas. A significant percentage (25-40%) of patients with tumours of the nerve sheath suffer from multiple neurofibromatosis (von Recklinghausen’s disease). This patient did not have von Recklinghausen’s disease (less than 5 ‘cafe au lait’ skin spots and no other nodule found on physical examination). The frequency of malignant thoracic neurogenic tumours (neurogenic sarcoma or malignant schwannoma) is quite low (4-13%) but it appears to be higher among patients with von Recklinghausen’s disease (10-20%)5.

Figures 8. A, B. Histology sections of the tumours. Surgical tissue biopsy detected two benign schwannomas.



Neurocytic tumours originate in peripheral nerve cells and include benign ganglioneuromas, malignant ganglioneuroblastomas and neuroblastomas, which are the most aggressive of the three types. Neuroblastoma is the most common extracranial solid tumour in childhood, accounting for 8-10% of all paediatric malignant tumours, and it is the most frequent tumour among infants6.

Neurogenic tumours are commonly found in the mediastinum, especially in the posterior mediastinum (75% to 95%) or in the chest wall, and they have a variety of clinical and histological features7. Thoracic neurogenic tumours usually originate in the neural crest during the development of peripheral nervous systems, such as those of the autonomic or paraganglionic nerves8. Such tumours are often asymptomatic, and are occasionally found on chest X-ray or chest CT. As they become larger in size, they can produce symptoms related to local compression, bone erosion, and spinal cord involvement. In the reported case the only symptom was moderate chest pain, chest X-ray revealed a lesion, and CT scan pinpointed the location of the tumour. The dual extrapleural location of the tumours (posterior mediastinum and chest wall) is noteworthy, it has not been reported before in the international bibliography. Less than 10% of primary thoracic neurogenic tumours originate in intercostal nerves 9. Such tumours often cause chest pain, which explains the finding that this patient’s symptoms derived from the chest wall tumour, although the other tumour had caused vertebral erosion.

Open biopsy is the standard procedure, which allows for decisions to be made about the appropriate therapeutic approach for the chest wall tumours. Over the last decade, CT guided needle biopsy has changed the management of these tumours. FΝΑ was used in this case, but the the presence of fibrosis led to negative results. Due to the uncertainty of the preoperative diagnosis, the increasing size of the tumour, and the possibility of malignancy, early surgical excision was considered to be the most acceptable strategy.

According to Yamaguchi M. et al only 1.7% of neurogenic tumours are malignant (malignant schwannoma), and the most common histological type is benign neurilemmoma (84%). The same authors report that MRI appears to be the best imaging method for pre-operative control of malignant neurogenic tumours1. In the reported case, 3D chest CT (a cost-effective method with an imaging contribution similar to MRI) proved to be a useful tool for planning the best possible treatment.

The double localization (in the middle of a rib and paravertebral) led to the decision for open surgery. Mediastinal neurogenic tumours can be removed with the use of thoracoscopy (VATS), which minimizes the access trauma and provides better view of the posterior mediastinum10,11. However in this case postero-lateral thoracotomy was chosen, in order to achieve safer manoeuvres in case the tumour was malignant, and to have the opportunity to remove a rib if necessary; this is a frequent procedure in tumours such as fibroelastoma, where because chemotherapy and radiotherapy have not been effective, the curative therapy is considered to be radical resection alone12.

The conclusion derived from the management of this case and from a short review of literature is that neurogenic tumours of the mediastinum, which are mostly asymptomatic, can be successfully studied with the use of 3D chest CT, and the ideal therapeutic approach includes surgical excision, which will also lead to the final diagnosis through the histological examination of the surgical biopsy.

References


1. Yamaguchi M, Yoshino I, Fukuyama S, et al. Surgical treatment of neurogenic tumors of the chest. Ann Thorac Cardiovasc Surg, 2004; 10(3):148-51.
2. Kumar S, Rafiq MU, Ahamed I, et al. Asymptomatic giant thoracic schwannoma. Ann Thorac Surg, 2006; 82(3):e26.
3. Tanaka O, Kiryu T, Hirose Y, et al. Neurogenic tumors of the mediastinum and chest wall: MR imaging appearance. J Thorac Imaging, 2005; 20(4):316-20.
4. Topcu S, Alper A, Gulhan E, et al. Neurogenic tumours of the mediastinum: a report of 60 cases. Can Respir J, 2000; 7(3):261- 5.
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7. Ribet ME, Cardot GR. Neurogenic tumors of the thorax. Ann Thorac Surg 1994; 58: 1091–5.
8. Whooley BP, Urschel JD, Antkowiak JG, et al. Primary tumors of the mediastinum. J Surg Oncol, 1999; 70: 95–9.
9. McClenathan JH, Bloom RJ. Peripheral tumors of the intercostal nerves. Ann Thorac Surg, 2004; 78(2):713-4.
10. Ishida T, Maruyama R, Saitoh G, et al. Thoracoscopy in the management of intrathoracic neurogenic tumors. Int Surg, 1996; 81: 347–9.
11. Satoda N, Hijiya K, Fukuse T. [Two-port video-assisted thoracoscopic excision of an intercostal schwannoma] Kyobu Geka, 2004; 57(3):198-200.
12. Uchiyama M, Shimoyama Y, Usami N. Primary pulmonary malignant schwannoma with extension to the tracheal carina. J Thorac Cardiovasc Surg, 2007; 133(1):265-7.

References