Malignant Transformation of Acoustic Neuroma/Vestibular Schwannoma 10 Years after Gamma Knife Stereotactic Radiosurgery

Abstract

Only a handful of cases of de-novo malignancies of the vestibulocochlear nerve have been reported. Even rarer is the malignant transformation of a previously histologically diagnosed benign vestibular schwannoma. We present the case of a young adult who had combined operative/Gamma knife treatment for a benign vestibular schwannoma, followed by further surgery 2 years later. He represented 10 years after original diagnosis with facial numbness and ataxia, MRI showing gross tumor recurrence. After radical resection, histology showed malignant transformation to a malignant peripheral nerve sheath tumor. Within 3 months there was rapid, aggressive recurrence with brainstem compression, requiring further surgery for brainstem decompression. Histology confirmed further de-differentiation to an anaplastic sarcoma. While awaiting radiotherapy the tumor recurred again, the patient succumbing. The patient had no features of neurofibromatosis type 2. In the literature there are 13 other cases of malignant vestibular schwannomata. Only six had radiotherapy and of these only two had histological confirmation of a benign lesion preradiotherapy. Neither of these had neurofibromatosis. Three other cases had histological proof of malignancy postradiosurgery, but with no preradiotherapy histology; of these, two were positive for neurofibromatosis. The tumor biology of vestibular schwannomata as well as the radiobiology in the context of malignant transformation is discussed.

Are the Current Treatment Strategies for Facial Nerve Schwannoma Appropriate Also for Complex Cases?

“…The tumor size remained stable with no sign of growth in 44.5% of the patients, decreased in 42.5%, and increased in 6.4%. Malignant transformation of intracranial schwannoma following stereotactic radiotherapy is an emerging topic in the worldwide literature [Norén, 1998;Hanabusa et al, 2001;Shin et al, 2002;Demetriades et al, 2010]. In 2011, a review of the literature by Husseini et al documented 26 cases of malignant transformation of irradiated vestibular schwannomas.…”

Recruitment and in situ Renewal Regulate Rapid Accumulation of CD11c+ Cells in the Lung following Intranasal Superantigen Challenge

“…CD11c expression is rather promiscuous, with a variety of cell types expressing this marker on their surface [38, 39]. Therefore studying the CD11c+ MHC II– cell population was difficult, as this population was heterogeneous.…”

Late malignant transformation of vestibular schwannoma in the absence of irradiation: case report

“…6,15,20 However, there is a concern that irradiation itself might play a causative role in secondary malignancy, which is a rare but a serious complication after radiation treatment, as reported in several case reports. 1,7,20,30,34 In a large study of 440 patients treated with Gamma Knife surgery for VS and with a median follow-up period of 12.5 years, the authors reported only one case of developing malignant change. The overall malignant transformation rate was calculated to 0.3%, with an annual incidence of 0.02%.…”

“…13,28 The short latency period in these cases could indicate that a malignant component already existed prior to irradiation, and might be aggravated by it, as radiation-induced malignancy usually develops over a longer period of time. 1,7,22,30 However, there is no consensus on the minimum latency period between radiation exposure and tumor development, and further work is necessary to establish a reference latency interval for radiation-induced tumors. Finally, in some case reports, patients with malignant VS have underlying NF2, a genetic condition known to be associated with a higher risk of malignant tumors, especially after radiation treatment, 2,32 and which contests Cahan's Criterion 4.…”