Malignant Transformation Of Vestibular Schwannoma Research Articles

Malignant transformation of vestibular schwannoma 29 years after Gamma Knife radiosurgery: illustrative case.

Vestibular schwannomas are common posterior fossa tumors, often managed with stereotactic radiosurgery (SRS) due to its low invasiveness and high tumor control rates. However, malignant transformation of vestibular schwannoma (MTVS) is a rare but serious complication with a poor prognosis. The authors present a case of MTVS occurring 29 years after initial SRS, the longest latency reported. A 68-year-old woman developed sudden facial nerve paralysis, with magnetic resonance imaging revealing tumor regrowth. Surgical removal and histopathological analysis confirmed malignant transformation, characterized by spindle-shaped atypical cells and significant p53 positivity. Despite multiple surgeries and radiation therapy, the tumor exhibited rapid regrowth and cerebrospinal dissemination, leading to a poor prognosis. This case underscores the critical importance of long-term monitoring after SRS, as malignant transformation can occur decades later. Additionally, it highlights the potential necessity for early intervention during malignant transformation to improve patient outcomes, despite the challenges in identifying effective treatments for MTVS. https://thejns.org/doi/10.3171/CASE24526.

Spontaneous malignant transformation of vestibular schwannoma: a case report and review of the literature

Background: The malignant transformation of vestibular schwannoma (VS) is a rare identity. We present a case of spontaneous transformation of VS and a short literature review. Case Presentation: A 41-year-old female had presented to us with vertigo, tinnitus, and hearing loss. She was diagnosed with left VS and underwent surgical resection. The initial histology was reported as benign grade 1 schwannoma. She subsequently presented to the hospital with hematoma in the tumor cavity after 4 and 5 months, respectively. Her repeat magnetic resonance imaging (MRI) showed growth of the residual tumor. She underwent a second translabyrinthine excision of the tumor. The histology from the second operation showed components of malignant transformation. One month postoperatively she suffered an acute decline in her conscious level. Repeat MRI demonstrated rapid regrowth of the tumor with further hemorrhage. In view of her rapid decline and perceived futility of further intervention and respecting her premorbid wishes, further escalation of therapy was deemed inappropriate. Conclusion: VS can transform into a malignant tumor even in the absence of radiation therapy. This may be considered in case of rapid regrowth of the tumor.

Evaluation of Reported Malignant Transformation of Vestibular Schwannoma: De Novo and After Stereotactic Radiosurgery or Surgery.

To critically analyze each reported case of malignant transformation of vestibular schwannoma (VS) after either stereotactic radiosurgery (SRS) or microsurgery (MS). We searched the Pubmed/Medline database using the relevant key words vestibular schwannoma, acoustic neuroma, malignant, transformation, radiation, induced, stereotactic, radiosurgery, malignancy, GammaKnife, and CyberKnife and combinations thereof. Inclusion criteria for malignant transformation of VS after SRS included histopathology of initially benign VS, subsequent histopathology confirming malignant VS, reasonable latency period between malignancy and benign diagnoses. A neurotologist and a skull base neurosurgeon independently assessed each case report for quality, entry, exclusion criteria, and comparability of extracted data. We calculated median age, latency times, and survival times for each case report. Malignant transformation has been documented to occur after either SRS or MS. Eight cases were included that showed histopathologic evidence of malignant transformation after SRS and MS. Four cases of malignant transformation were included that demonstrated malignant transformation after MS only. Malignant transformation of VS can also occur de novo, and de novo malignant VSs are also encountered, which can confound a causal inference from either SRS or MS. Eighteen cases of primary malignant VS were included. Studies that were identified but not included in the review are summarized and tabulated. We found 12 studies of malignant transformation associated with NF2. The potential mechanism leading to malignant transformation of VS seems more obvious for SRS and is less understood for MS. Given a low incidence of de novo malignant schwannoma, the possibility that these are spontaneous events in either setting cannot be ruled out. Risk of malignant transformation of VS after either SRS or MS is not zero; however, the magnitude of this risk is probably minimal based on the evidence from eight histopathologically confirmed cases.

What is the risk of malignant transformation of vestibular schwannoma following radiosurgery?

Since the use of radiosurgery to treat vestibular schwannoma (VS) has only become widespread over the last several decades, we are just now beginning to see the long-term outcomes and side effects of this treatment. One particularly concerning complication is malignant transformation of a benign lesion. Although the malignant-inducing potential of radiation is well documented for traditional radiation therapy, there are limited data available regarding this complication in the context of stereotactic radiosurgery (e.g., Gamma Knife [Elektra, Stockholm, Sweden] and Cyberknife [Accuray, Sunnyvale, CA]) for vestibular schwannoma. Compared to standard radiation therapy, the irradiated volume with radiosurgery is significantly smaller, and the high single doses given to this small target should theoretically lead to cytotoxicity and not mutagenicity. However, there have been several recent case reports in the literature of skull base malignancies following stereotactic radiosurgery. These criteria are problematic for our purposes because the diagnosis of a vestibular schwannoma is based on clinical and radiographic diagnosis and pretreatment biopsy is rarely obtained. Given the rarity of aggressive lesions, biopsying every patient that presents with a VS would add time, morbidity, and cost while providing minimal benefit in terms of management and decision making. A recent review by Demetriades et al. found 14 cases of malignant vestibular schwannoma reported in the literature.2 Only six of the 14 patients actually had prior radiotherapy. Of those six, only three had a pathology-proven benign lesion prior to treatment. Of the five cases of malignant VS in the absence of radiosurgery, two even had initial histology showing benign disease.2 These cases highlight the difficulty of definitively establishing a causal relationship between radiosurgery and malignant transformation. A 2014 review by Patel and Chiang examines not only cases of malignant transformation of VS but also cases of radiation-induced malignancy arising from surrounding normal tissue in the treatment field for VS.3 Of 22 cases treated for VS, 13 transformed into malignant peripheral nerve-sheath tumors, whereas five developed glioblastoma multiforme and four developed sarcomas. Overall, the authors estimated the risk of developing a malignancy after stereotactic radiosurgery to be 0.04% at 15 years posttreatment. This calculation is based on stereotactic radiosurgery for any benign lesion. There are significant differences in treatment dose and volume depending on the initial pathology. As with any treatment decision, patient selection is critical. Age at the time of exposure and certain genetic susceptibilities such as neurofibromatosis type 2 (NF-2) have been identified as increasing the risk of radiation-induced oncogenesis. A review by Hosseini et al. also highlighted a possible association with initial tumor size.4 In their review of 17 cases of malignant transformation of VS, none of the patients had a tumor less than 2.5 cm in size. Thirteen of the 17 cases were in patients with NF-2. Hosseini postulates that radiosurgery serves as the final genetic hit that induces malignant transformation in already mutated cells.4 This theory could also explain the increased risk in younger patients. In this scenario, perhaps radiosurgery serves as an earlier genetic insult. Younger patients, having a longer life ahead, have more opportunity to acquire additional mutations in those cells' DNA, eventually leading to malignant transformation. As the duration of posttreatment follow-up increases for these patients, more specific criteria regarding high-risk patients will be established. Hasegawa et al., in a large study of 440 patients treated with gamma knife surgery for VS and followed for a median of 12.5 years, reported only one case of malignant degeneration.5 The patient did not have a preradiosurgery biopsy. Even with the assumption that this lesion was in fact benign pretreatment, the overall malignant transformation rate was calculated as 0.3%, and the annual incidence of malignant change was 0.02%.5 Radiosurgical treatment of vestibular schwannomas is safe and effective. The risk of malignant degeneration is acceptably low for the majority of patients. Caution is particularly required when counseling young patients, patients with genetic susceptibility, and patients with large tumors. This article references one level I, one level III, and three level IV papers.

Unique case of malignant transformation of a vestibular schwannoma after fractionated radiotherapy

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.