Surgery of benign neurogenic tumors in adults: single institution experience

The objective of this work is to review retrospectively our experience with 17 patients presenting with benign neurogenic tumors, managed in the department of thoracic surgery, Mohamed V Military Academic Hospital, Rabat, Morocco. Between 2003 and 2011, seventeen patients were surgically treated for benign neurogenic tumors of the mediastinum, among 112 mediastinal tumors operated during the same period. The mean age of the 17 patients was 46 years, including 11 females and 6 males. The information about clinical presentation, diagnostic procedures, surgical techniques and postoperative follow-up were extracted and analyzed from medical records. Symptoms related to the tumor were found in 13 patients (76,4%). The posterior mediastinum was the principal location (16 cases: 94%). Intraspinal extension was shown through MRI in one case. Surgical extirpation was complete in all patients. There were no tumor-related deaths and no significant complications. There were 13 schwannomas, 2 neurofibromas and 2 ganglioneuromas. Neurogenic tumors of the mediastinum in adults are mostly benign. Their only treatment is surgical extirpation. Video-assisted thoracoscopic resection is currently the best approach in selected patients.


Introduction
Benign neurogenic tumors are relatively the third most frequent of all mediastinal tumors behind thymomas and probably lymphomas (20% of all primitive tumors of the mediastinum and 75% of the tumors of posterior mediastinum) [1]. They are neoplasms arising from all the components of intrathoracic nervous formations. The rate of malignancy is very low in adults in comparison to pediatric population (6% and 40% respectively) [2]. The posterior mediastinum rich in neurogenic elements (sympathetic chain, intercostal nerves, vagus nerves...) remains their elective localization [3], especially along the costovertebral gutter. The posterolateral thoracotomy has been the traditional surgical approach, in the aim to carry out the complete resection of these tumors; generally benign. Outside certain contraindications, the video-assisted thoracoscopic surgery (VATS) is actually a good alternative for excising such small tumors [4]. The objective of this study was to report our experience in the management of this disease, since its discovery among our patients, until ensuring regular follow-up after surgery, in order to better relate our results.

Methods
The register of hospitalization of the department of thoracic surgery,

Results
The discovery of the tumor was related to the presence of  Table   1).

Discussion
In adults, neurogenic tumors of the mediastinum are benign in approximately 92% of cases [5,6]. They are the most common type In general, the preoperative diagnosis of benign neurogenic tumor of the mediastinum is most often established by radiographic imaging alone. Chest X-ray can diagnose the thoracic topography of the tumor (often posterior) [10]. CT scan provides information about the topography, the size, the density and the enhancement of the tumor following contrast injection, the presence of calcifications and the relations with adjacent structures; what are criteria for the diagnosis and to predict the difficulties of resection [10,11]. In all our patients the preoperative diagnosis was successfully established by CT scan. MRI should be performed when the tumor is suspected to extend into the spinal canal, so as to determine the longitudinal extent of the tumor in the spine for better neurosurgical procedure [12]. In adults, nerve sheath tumors, such as schwannomas and neurofibromas, are the most frequent followed by the tumors of the autonomic system, such as ganglioneuromas. Tumors arising from the paraganglionic system (paragangliomas) are very rare [7].
Schwannomas, also called neurilemmomas, are the most frequent tumors of nerve sheath, usually developed from the sensory root of an intercostal nerve, and rarely from the phrenic or vagus nerve [13]. Nerve cell tumors of autonomic system are more common in children. Their reported risk of malignancy is between 27% and 76% [14,15]. The malignancy rate in adults is reported to be between 4% and 12% [7,16], represented mainly by malignant shwannoma. In our practice, most tumors were derived from the nerve sheaths (88%), among witch shwannoma was the most frequent (76,5%) of all the histological types. Malignant transformation of a pre-existing shwannoma is very rare, explaining that malignancy was found in none of our patients. Indeed, the rate of recurrence after complete resection is almost null. Schwannomas and ganglioneuromas showed good results after surgery, however the risk of malignant transformation should be considered in neurofibromas, especially when associated to Von Recklinghaussens disease [24].

Conclusion
In conclusion, surgery is the treatment of choice for neurogenic (mostly benign) tumors of the mediastinum in adults. VATS resection is increasingly reported, with convincing results, to be a good alternative in managing benign neurogenic tumors of the thorax in selected patients. Recurrence or the need to an additional therapy should no longer be considered after complete resection.
The combined neurosurgical and thoracic approach is the rule in the surgical management of Dumbell tumors.

Competing interests
The authors declare no competing interests.

Authors' contributions
All authors have read and approved the final version of the manuscript.