Abstract
Objective
Malignant transformation of vestibular schwannoma is considered a rare clinical entity. Radiotherapy, as a treatment option for vestibular schwannoma, is regarded as a potential risk factor for secondary malignancy. Recently, radiotherapy with dose fractionation has been proposed, intended to diminish the risk of radiation-induced neuropathy.
Case Presentation
The aim of the present study is to report the first case, to the best of our knowledge, of malignant transformation of a residual vestibular schwannoma 19 years after fractionated radiotherapy, describing its characteristics with regard to those previously reported in the literature.
Conclusions
The main purpose of the present work is to state that the knowledge of the iatrogenic potential pitfalls of any technique of radiotherapy in clinical oncology is becoming a necessity. Finally, our report demonstrates that the irradiated patients must be monitored for life because a secondary malignancy may appear after a very long delay.
1
Introduction
Treatment options for vestibular schwannoma (VS) include either surgery or radiotherapy. Commonly, radiotherapy is delivered using stereotaxy with a single fraction, involving a gamma-knife (gamma-knife radiosurgery; GKR). Recently, radiotherapy with dose fractionation (fractionated radiotherapy; FRT) has been proposed, intended to diminish the risk of radiation-induced neuropathy .
Malignant transformation of benign cranial nerve sheath tumors has been reported on very few occasions . Until now, only 8 cases of secondary malignancies attributable to GKR have been published . No case of malignancy secondary to FRT for treatment of VS has been reported.
The aim of the present study is to report the first case, to the best of our knowledge, of malignant transformation of a residual VS 19 years after FRT, describing its characteristics with regard to those previously reported in the literature.
2
Materials and methods
2.1
Case presentation
In 1986, a 42-year-old woman was operated on for giant left-sided VS by a translabyrinthine approach ( Fig. 1 A ). After a very difficult and long surgery, a partial excision of the tumor, using a translabyrinthine approach, was performed because of its close association to the lower cranial nerves. The patient’s postoperative course was marked by total deafness and transitory facial nerve paralysis, being partially recovered 1 year later (House and Brackmann grade 2). The histopathological examination of the tumor revealed a typical benign schwannoma ( Fig. 2 A –B). Initially, a second surgical procedure was planned for the excision of the residual lesion ( Fig. 1 B). However, the recovery of facial nerve’s function and the stability of the tumor volume, findings of a computed tomography scan, were the reasons for choosing a complementary irradiation using conformal FRT (50 Gy, with 4 converging beams, 1.8 Gy per fraction). Clinical and radiological survey was uneventful until July 2005. At that time, the patient reported an episode of left facial paralysis and symptoms of transitory diplopia. The magnetic resonance imaging (MRI) scan revealed an important increase in the volume of the residual tumor filling the cerebellopontine angle ( Fig. 1 D) compared with the MRI scan findings a few months previously ( Fig. 1 C). In December 2005, the patient was reoperated on by the same approach. The tumor was in close contact with the lower cranial nerves, pushing medially the abducent nerve. The trigeminal nerve was laminated; and the facial nerve was dissected from the tumor, remaining stimulable during surgery. Tumor exeresis was complete. However, patient had complete paralysis of facial and abducent nerves.
Histopathological examination of the tumor demonstrated a malignant peripheral nerve sheath tumor, with characteristic fasciculated growth pattern of densely packed hyperchromatic spindle cells. The cells contained eosinophilic cytoplasm and elongated and hyperchromatic nuclei with mitotic activity ( Fig. 3 A ). In immunohistochemistry, scattered tumor cells expressed S-100 protein ( Fig. 3 B).
After a multidisciplinary consultation, close clinical and imaging monitoring was proposed. At 5-month postoperative assessment, the MRI failed to demonstrate any tumor relapse. A year later, a small nodular mass appeared in the lower part of the cerebellopontine angle, evoking a tumor relapse.
2
Materials and methods
2.1
Case presentation
In 1986, a 42-year-old woman was operated on for giant left-sided VS by a translabyrinthine approach ( Fig. 1 A ). After a very difficult and long surgery, a partial excision of the tumor, using a translabyrinthine approach, was performed because of its close association to the lower cranial nerves. The patient’s postoperative course was marked by total deafness and transitory facial nerve paralysis, being partially recovered 1 year later (House and Brackmann grade 2). The histopathological examination of the tumor revealed a typical benign schwannoma ( Fig. 2 A –B). Initially, a second surgical procedure was planned for the excision of the residual lesion ( Fig. 1 B). However, the recovery of facial nerve’s function and the stability of the tumor volume, findings of a computed tomography scan, were the reasons for choosing a complementary irradiation using conformal FRT (50 Gy, with 4 converging beams, 1.8 Gy per fraction). Clinical and radiological survey was uneventful until July 2005. At that time, the patient reported an episode of left facial paralysis and symptoms of transitory diplopia. The magnetic resonance imaging (MRI) scan revealed an important increase in the volume of the residual tumor filling the cerebellopontine angle ( Fig. 1 D) compared with the MRI scan findings a few months previously ( Fig. 1 C). In December 2005, the patient was reoperated on by the same approach. The tumor was in close contact with the lower cranial nerves, pushing medially the abducent nerve. The trigeminal nerve was laminated; and the facial nerve was dissected from the tumor, remaining stimulable during surgery. Tumor exeresis was complete. However, patient had complete paralysis of facial and abducent nerves.
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