Malignant transformation of a recurrent vestibular schwannoma

Intracranial malignant peripheral nerve sheath tumor: A case report and comprehensive literature review

Background

Malignant peripheral nerve sheath tumors (MPNSTs) are rare malignant soft-tissue sarcomas arising from peripheral nerves. Little data exist regarding MPNST originating intracranially. Here, we present a 7th/8th nerve complex MPNST, discuss the treatment strategy and patient outcome, and provide a comprehensive review of existing literature.

Methods

Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, PubMed and crossed references were queried, yielding 37 publications from 1952 to the present. Fifty-three cases of primary intracranial and extra-axial MPNST were identified.

Results

We additionally report a 40-year-old female presented with acute onset dizziness and subsequent hearing loss with associated right-sided facial numbness. Magnetic resonance imaging revealed a 0.5 cm × 1.7 cm enhancing lesion within the right internal auditory canal extending into the cerebellopontine angle. The patient was initially treated with retro sigmoid craniotomy for tumor resection followed by a trans labyrinth approach for residual tumor resection. She completed adjuvant fractionated radiation therapy and underwent facial nerve transfer to restore complete hemifacial paralysis. The most common cranial nerves involved were V and VIII (43.4% each), with 66% of patients male and 34% female. The average age was 43.4 ± 17.4 years. The mean survival time for reported non-survivors after tissue diagnosis was 15 ± 4 months. Two-year survival for patients receiving gross total resection was 33.3% versus 22.8% with subtotal resection.

Conclusion

MPNSTs comprise a group of highly aggressive neoplasms that rarely arise intracranially. Gross total surgical resection should be pursued when feasible.

Malignant peripheral nerve sheath tumour transformation of histological benign vestibular schwannoma after stereotactic radiosurgery in patients without neurofibromatosis

Stereotactic radiosurgery (SRS) poses a minimal but important risk for tumour transformation, typically occurring 8-10 years after the treatment. Malignant peripheral nerve sheath tumour (MPNST) is the most common tumour arising from a vestibular schwannoma treated with SRS, with only 14 cases previously reported. We present the fifteenth case and describe its evolution and clinical course. A 56-year-old man without a history of neurofibromatosis was diagnosed 9 years prior with a vestibular schwannoma. SRS to the residual tumour was given 3 months later. During the current hospitalisation, he was reoperated where histology confirmed a MPNST. All 15 MPNST cases were analysed, showing a 77% female predominance presenting a malignant transformation at a mean age of 51. The diagnosis was made at a mean time of 74 months after SRS. The mean survival time after diagnosis was 16 months. MPNST arising from benign vestibular schwannoma after SRS treatment is an uncommon but devastating complication.

Tumor Control Following Stereotactic Radiosurgery in Patients with Vestibular Schwannomas - A Retrospective Cohort Study

BACKGROUND

To better counsel vestibular schwannoma patients, it is necessary to understand the tumor control rates of stereotactic radiosurgery (SRS).

OBJECTIVES

To determine tumor control rates, factors determining control and complication rates following SRS.

METHODS

Tertiary hospital retrospective cohort.

RESULTS

579 tumors (576 patients) were treated with SRS. 477 tumors (474 patients, 82%) had ≥1 year follow up and 60% (344) ≥3 years follow up. 88% of tumors had primary SRS and 6.7% salvage SRS. Median follow up time was 4.6 years. At 3 years, the tumor control rate of primary SRS was 89% (258 of 290) in sporadic tumors compared to 43% in Neurofibromatosis type II (3 of 17) (p < 0.01). Our bivariable survival data analysis showed that Neurofibromatosis type II, documented pre-SRS growth, tumor measured by maximum dimension, SRS given as nonprimary treatment increased hazard of failure to control. There was one case of malignancy and another of rapid change following intra-tumoral hemorrhage. For tumors undergoing surgical salvage (25 of 59), 56% had a total or near-total resection, 16% had postoperative CSF leak, with 12% new facial paralysis (House-Brackmann grade VI) and worsening of facial nerve outcomes (House-Brackmann grade worse in 59% at 12 mo).

CONCLUSIONS

Control of vestibular schwannoma after primary SRS occurs in the large majority. Salvage surgical treatment was notable for higher rates of postoperative complications compared to primary surgery reported in the literature.

Outcomes of stereotactic radiosurgery in young adults with vestibular schwannomas

PURPOSE

Vestibular schwannomas (VSs) are comparatively rare in younger patients, and stereotactic radiosurgery (SRS) outcome data are limited. We aimed to evaluate long-term SRS outcomes concerning sporadic VSs in patients aged ≤ 40 years.

METHODS

Of 383 patients with VS who had undergone SRS at our institution between 1990 and 2017, we retrospectively compared younger and older patients' tumor control and radiation-induced complication rates using case-control propensity score (PS) matching.

RESULTS

The mean follow-up was 83 and 92 months in older and younger patients, respectively. Compared with older patients, younger patients were more likely to have a history of resection (20% vs. 39%, p = 0.006) and be treated with higher marginal doses (median, 12 Gy vs. 14 Gy; p = 0.014). Cumulative 5- and 10-year tumor control rates were higher in older patients (97.7% and 93.9%, respectively) than in younger patients (90.2% and 85.4%, respectively, p = 0.024). After PS matching, younger patients' cumulative tumor control rates (93.6%, 85.4%, and 85.4% at 5, 10, and 15 years, respectively) were similar to those of older patients (p = 0.411). No significant between-cohort differences in hearing preservation rates or other cranial nerve complications were observed. Two younger patients had malignant tumors several years post-SRS, with one patient having confirmed histological transformation.

CONCLUSIONS

SRS is equally effective for younger and older patients. Complications other than hearing deterioration are uncommon. However, malignant transformation is possible, and long-term post-SRS surveillance MRI is important. These data are useful for decision-making involving young adults with VSs.

Malignant Transformation in Vestibular Schwannoma: Clinical Study With Survival Analysis

Aim

Vestibular schwannomas (VSs) are generally considered benign tumors, and malignant transformation of VSs (MTVSs) are rare findings. The clinical features, treatment strategy, outcomes and prognostic factors remain unclear. We endeavored to analyze the natural history, management, outcomes and prognostic factors of MTVSs.

Materials and Methods

The clinical features, radiologic findings, pathological investigations and surgical outcomes of 4 patients with MTVSs treated at the authors' institution between 2010 and 2019 were retrospectively collected. Related literature published until December 2019 (63 articles, 67 patients) was evaluated. The authors also made a pooled analysis to evaluate the risk factors for overall survival (OS) time.

Results

Of the 4 cases in our series, 3 cases were malignant transformation following previous treatment (surgery and radiosurgery) and 1 was primary MTVS. Of the 71 MTVSs from the literature, 27 were male and 39 were female, with the mean age of 47.2 ± 17.5 years old. Twelve patients (18.5%) were diagnosed with NF2 (15.4%) or NF1 (3.1%). Forty-three (61.4%) patients underwent previous treatment (surgery and/or radiotherapy) prior to the pathological diagnosis of MTVSs. The mean size of the MTVSs was 35.1 ± 13.2mm. The mean Ki-67 index was 30.6% ± 18.8%. Twenty-four (49.0%) patients underwent gross total resection, 25 (51.0%) patients underwent incomplete resection. Twenty-five (44.6%) underwent adjuvant radiotherapy (RT) postoperatively. During the average follow-up of 9.9 ± 9.5 months (range, 0-40 months), 37 (82.2%) patients developed a local recurrence or metastasis. Forty-seven (73.4%) patients died of tumor progression or postoperative complications. The overall 1-year and 2-year survival rate was 42.3% and 18.6% respectively. Log-rank testing for Kaplan-Meier survival analysis identified that size (P = 0.047) and adjuvant radiotherapy (P=0.001) were significant prognostic factors for OS. Multivariate analysis revealed that adjuvant RT was the only prognostic factor for longer OS (P = 0.005).

Conclusions

MTVSs are rare, fatal disease, prone to recur and metastasize rapidly, resulting in death in most of the cases. We found that GTR did not improve the survival in MTVSs but postoperative adjuvant RT can significantly improve the OS, and we recommend early postoperative RT in MTVSs regardless of extent of resection.

High-Grade Sarcoma Arising within a Previously Irradiated Vestibular Schwannoma: A Case Report and Literature Review

BACKGROUND

Vestibular schwannomas are benign tumors of the cerebellopontine angle that are often treated with radiation therapy. Radiation therapy maintains good tumor control rates but involves a small risk of radiation-induced malignancies. We present a case of high-grade sarcoma arising within a previously irradiated vestibular schwannoma and a literature review of this rare but important clinical entity.

METHODS

A 66-year-old woman presented with rapid clinical and radiographic deterioration 17 years after receiving stereotactic radiosurgery for vestibular schwannoma. After resection, pathology revealed a high-grade sarcoma arising within a conventional schwannoma. After further decline and tumor growth, the patient died of her disease 7 months postoperatively. Literature review was performed using PubMed and EMBASE databases and key words "vestibular schwannoma," "acoustic," "triton," "malignant," "sarcoma," "malignant peripheral nerve sheath tumor," "radiation," and "radiosurgery." All previous cases and the clinical circumstances related to these radiation-induced malignancies were assessed and quantified.

RESULTS

The systematic review yielded 20 prior cases of radiation-induced malignant transformation of a vestibular schwannoma in patients without neurofibromatosis. Most tumors (60%) transformed into malignant nerve sheath tumors. At the time of presentation, 70% of patients had new cranial neuropathies, and all had evidence of tumor growth with brainstem compression. Prognosis was poor with mean time to death of 7.6 months.

CONCLUSIONS

Radiation-induced malignant transformation of vestibular schwannomas is a rare but important clinical entity. Given its scarcity, the risk of malignancy should not sway initial management, but rapid clinical deterioration and radiographic growth during follow-up should prompt consideration of malignant transformation.

Glioblastoma multiforme as a secondary malignancy following stereotactic radiosurgery of a meningioma: case report

The documentation and exact incidence of stereotactic radiosurgery (SRS)-induced neoplasia is not well understood, with most literature restricted to single case reports and single-center retrospective reviews. The authors present a rare case of radiosurgery-induced glioblastoma multiforme (GBM) following radiosurgical treatment of a meningioma. A 74-year-old patient with a sporadic meningioma underwent radiosurgery following surgical removal of a WHO grade II meningioma. Eighteen months later she presented with seizures, and MRI revealed an intraaxial tumor, which was resected and proven to be a glioblastoma. As far as the authors are aware, this case represents the third case of GBM following SRS for a meningioma. This report serves to increase the awareness of this possible complication following SRS. The possibility of this rare complication should be explained to patients when obtaining their consent for radiosurgery.

The impact of the MIB-1 index on facial nerve outcomes in vestibular schwannoma surgery

Background

Facial nerve palsy is a severe morbid condition that occurs after vestibular schwannoma (VS) surgery. The objective of this study was to evaluate facial nerve outcomes based on surgical techniques, tumour size, and immunohistochemical factors.

Methods

One hundred eighteen patients with VS were retrospectively analysed. Gross total resection (GTR) was achieved in 83 patients, and subtotal resection (STR) was achieved in 35 patients. Follow-up was 60 months (median). Facial nerve outcomes were assessed for 24 months after surgery. Analysis of the MIB-1 index was performed in 114 patients (97%) to evaluate recurrence and facial nerve outcomes.

Results

Immediately after surgery, 16 of 35 patients (45.7%) with STR and 21 of 83 patients (25.3%) with GTR had a good (House-Brackmann (HB) score ≤ 2) facial nerve outcome (p = 0.029). Semi-sitting positioning (p = 0.002) and tumour size class of 3 (> 4 cm) were also associated with worse HB outcomes after 2 years (p = 0.004) in univariate analyses. The MIB-1 index was significantly correlated with diffuse infiltration of tumour-associated CD45⁺ lymphocytes (r = 0.63, p = 0.015) and CD68⁺ macrophages (r = 0.43, p = 0.021). ROC analysis found an AUC of 0.73 (95% CI = 0.60–0.86, p = 0.003) for the MIB-1 index in predicting poor facial nerve outcomes. Binary logistic regression analysis revealed an MIB-1 index ≥ 5% (16/28 (57.1%) vs. 5/40 (12.5%); p < 0.001, OR = 14.0, 95% CI = 3.2–61.1) and a tumour size class of 3 (6/8 (75.0%) vs. 2/8 (25.0%); p = 0.01, OR = 14.56, 95% CI = 1.9–113.4) were predictors of poor HB scores (≥ 3) after 1 year.

Conclusions

An MIB-1 index ≥ 5% seems to predict worse long-term facial nerve outcomes in VS surgery.

TIM-3 plays a more important role than PD-1 in the functional impairments of cytotoxic T cells of malignant Schwannomas

Cancer immunotherapy using cytotoxic T cells demonstrates dramatic survival benefits in lymphomas, but its efficacy in solid tumors is limited. Here, we investigated the possibility of using cytotoxic T cells to treat malignant Schwannoma, a rare but aggressive nerve sheath tumor, by examining the native T-cell immunity in the host. We found that compared to CD8⁺ T cells from healthy controls or benign Schwannoma patients, the CD8⁺ T cells from malignant Schwannoma patients were present at normal frequencies but were substantially enriched with PD-1^-TIM-3⁺ and PD-1⁺TIM-3⁺ cells. Compared to the PD-1^-TIM-3^- CD8⁺ T cells, the PD-1^-TIM-3⁺ and PD-1⁺TIM-3⁺ CD8⁺ T cells presented significantly lower proliferation capacity, reduced interleukin 2 and interferon gamma expression, and/or dramatically decreased perforin and granzyme B secretion, indicating a whole-spectrum immunosuppression and reduced cytotoxicity. TIM-3 expression alone was associated with lower proliferation and less perforin and granzyme B secretion, whereas PD-1 expression alone was not associated with functional impairments, suggesting that TIM-3 expression was a better marker of exhausted CD8⁺ T cells. The expression of galectin 9, a TIM-3 ligand, in CD4⁺ Th cells was significantly elevated in malignant, but not benign, Schwannoma patients and were enriched in CD25⁺ Treg cells. Both the PD-1^-TIM-3⁺ and PD-1⁺TIM-3⁺ CD8⁺ T cells responded to Treg-mediated and galectin 9-mediated suppression, whereas the PD-1⁺TIM-3^- CD8⁺ T cells only responded to Treg-mediated suppression. In resected tumors, the malignant Schwannomas had more tumor-infiltrating CD4⁺ and CD8⁺ T cells than the benign Schwannomas, but a large fraction of these tumor-infiltrating CD4⁺ and CD8⁺ T cells expressed PD-1 and/or TIM-3, which indicated that their antitumor immunity was compromised. Together, our results suggested that PD-1 and TIM-3 blockade might be necessary in developing effective immunotherapeutic strategies in malignant Schwannoma, in which TIM-3 may play a more important role.

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

OBJECTIVE

To critically analyze each reported case of malignant transformation of vestibular schwannoma (VS) after either stereotactic radiosurgery (SRS) or microsurgery (MS).

DATA SOURCES

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.

STUDY SELECTION

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.

DATA EXTRACTION

A neurotologist and a skull base neurosurgeon independently assessed each case report for quality, entry, exclusion criteria, and comparability of extracted data.

DATA SYNTHESIS

We calculated median age, latency times, and survival times for each case report.

RESULTS

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.

CONCLUSION

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.

Malignant peripheral nerve sheath tumors of the eighth cranial nerve arising without prior irradiation

OBJECTIVE Malignant peripheral nerve sheath tumors (MPNSTs) of the eighth cranial nerve (CN) are exceedingly rare. To date the literature has focused on MPNSTs occurring after radiation therapy for presumed benign vestibular schwannomas (VSs), while MPNSTs arising without prior irradiation have received little attention. The objectives of the current study are to characterize the epidemiology, clinical presentation, disease course, and outcome using a large national cancer registry database and a systematic review of the English literature. Additionally, a previously unreported case is presented. METHODS The authors conducted an analysis of the Surveillance, Epidemiology, and End Results (SEER) database, a systematic review of the literature, and present a case report. Data from all patients identified in the SEER database with a diagnosis of MPNST involving the eighth CN, without a history of prior radiation, were analyzed. Additionally, all cases reported in the English literature between January 1980 and March 2015 were reviewed. Finally, 1 previously unreported case is presented. RESULTS The SEER registries identified 30 cases between 1992 and 2012. The average incidence was 0.017 per 1 million persons per year (range 0.000-0.0687 per year). The median age at diagnosis was 55 years, and 16 (53%) were women. Thirteen cases were diagnosed upon autopsy. Of the 17 cases diagnosed while alive, the median follow-up was 118 days, with 3 deaths (18%) observed. When compared with the incidence of benign VS, 1041 VSs present for every 1 MPNST arising from the eighth CN. Including a previously unreported case from the authors' center, a systematic review of the English literature yielded 24 reports. The median age at diagnosis was 44 years, 50% were women, and the median tumor size at diagnosis was 3 cm. Eleven patients (46%) reported isolated audiovestibular complaints typical for VS while 13 (54%) exhibited facial paresis or other signs of a more aggressive process. Treatment included microsurgery alone, microsurgery with adjuvant radiation, or microsurgery with chemoradiation. Sixty-one percent of patients receiving treatment experienced recurrence, 22% of which were diagnosed with drop metastases to the spine. Ultimately, 13 patients (54%) died of progressive disease at a median of 3 months following diagnosis. The ability to achieve gross-total resection was the only feature that was associated with improved disease-specific survival. CONCLUSIONS MPNSTs of the eighth CN are extremely rare and portend a poor prognosis. Nearly half of patients initially present with findings consistent with a benign VS, often making an early diagnosis challenging. In light of these data, early radiological and clinical follow-up should be considered in those who elect nonoperative treatment, particularly in patients with a short duration of symptoms or atypical presentation. These data also provide a baseline rate of malignancy that should be considered when estimating the risk of malignant transformation following stereotactic radiosurgery for VS.

Malignant transformation in vestibular schwannoma: report of a single case, literature search, and debate

OBJECT

The significance of radiation in the induction of malignancy in vestibular schwannomas (VSs) after radiosurgery is unclear despite an increasing number of case reports. The authors describe a new case of verified malignant transformation in a vestibular schwannoma (MTVS) and provide a new evaluation of such cases previously reported in the literature.

METHODS

A 46-year-old woman underwent subtotal resection of a right-sided VS in 2004. The histological characteristics of the lesion were typical and benign. In early 2007 Gamma Knife surgery (GKS) was performed to treat a residual enlarging remnant. The radiosurgery parameters included the following: target volume 3.5 cm(3), prescription dose 12 Gy, prescription isodose 45%, maximum dose 26.7 Gy, and coverage 97%. At 2 years' follow-up the lesion was enlarged to 5.2 cm(3), but by 5 years it had decreased to 2.3 cm(3). Six months later the lesion was 8.4 cm(3). Repeated surgery was performed, and a histological analysis revealed a malignant peripheral nerve sheath tumor. The case was further managed with repeated GKS performed in the spring of 2013. At that time, the radiosurgery parameters included the following: target volume 3.5 cm(3), prescription dose 16 Gy, prescription isodose 45%, maximum dose 35.6 Gy, and coverage 91%. This Gamma Knife Department has treated a total of 205 patients with VS (local incidence of MTVS 0.49%). A search of the literature published up to and including 2013 was performed using PubMed as well as more informal search methods.

RESULTS

This patient is the 29th reported case of MTVS after radiation therapy. Of these cases, 40.7% were patients with neurofibromatosis (NF). In those cases in which histology showed tumors with previously benign characteristics, totally conforming to the criteria for MTVS, the mean delay to malignant expression was 68 months (median delay 72 months). The authors also retrieved papers reporting 30 cases of malignant VS in patients who had not undergone radiation treatment. Five of those cases were malignant transformation of a benign entity, and in 4 of them histology had verified that the initial disease was benign. In those 4 cases, there was a mean delay to malignant expression of 7.2 months (median delay 8 months).

CONCLUSIONS

Despite more frequent reports of MTVS after radiation treatment recently, there has been no accurate quantification of the risk, except in patients with NF, in whom the incidence of malignancy is high in relation to the numbers treated. The present analysis indicates that the risk of malignancy over 20 years in cases in which no radiation treatment has occurred is 1.32-2.08 per 100,000, and this risk decreases to 1.09-1.74 per 100,000 if cases of NF are excluded. After radiation treatment, the overall risk over 20 years is 25.1 per 100,000, and this risk decreases to 15.6 per 100,000 if cases of NF are excluded. Radiation treatment increases the risk by approximately 10 times in non-NF cases.

MPNST after Radiosurgery: A Report and Review of the Literature

OBJECTIVE

To report an unusual case of malignant degeneration in a ganglioneuroma of the jugular foramen post stereotactic radiosurgery as well as to systematically review the pertinent literature involving radiosurgery associated malignancies.

BACKGROUND

Ganglioneuromas are uncommon lesions of the peripheral nervous system and infrequently reported in the head and neck region. There have been no previously described cases of ganglioneuromas occurring in the jugular foramen. Malignant degeneration of these lesions is rarely described, especially in the context of radiosurgery. Radiosurgery associated malignancies overall are exceptionally rare and only a limited number of cases have been reported.

RESULTS/CONCLUSIONS

We describe a case of a ganglioneuroma occurring in the jugular foramen and mimicking the appearance of a jugular foramen schwannoma. This lesion underwent stereotactic radiosurgery and developed a delayed degeneration into a malignant nerve sheath tumor. The occurrence of ganglioneuroma in this region has not been previously described and presumed malignant degeneration is even rarer. This case highlights a previously understated risk associated with stereotactic radiation treatments. To date, 33 previous cases of stereotactic radiosurgery associated malignancies have been reported. We review the pertinent details of these cases. We caution that as follow up periods and awareness increases, reports such as this may become increasingly common.

Tumeurs malignes des gaines nerveuses périphériques après la radiochirurgie : à propos d'un cas et revue de littérature.

Secondary neoplasms after stereotactic radiosurgery

OBJECTIVE

The use of medical radiation has increased 6-fold in the past 30 years. Within neurosurgery, the advent of stereotactic radiosurgery (SRS) has significantly altered the treatment paradigm for both benign and malignant central nervous system diseases. With this increased reliance on radiation has come a responsibility to identify the long-term risks, including the potential development of radiation-induced neoplasms. Although the data regarding traditional radiation exposure and its subsequent risks are well-defined, the data for SRS is less developed.

METHODS

We reviewed the published literature to more accurately define the risk of developing secondary neoplasms after stereotactic radiosurgery.

RESULTS

A total of 36 cases of SRS-induced neoplasms were identified. More than half of the cases had an initial diagnosis of vestibular schwannoma. Overall, the risk of developing an SRS-induced neoplasm is approximately 0.04% at 15 years.

CONCLUSION

The risk of developing an SRS-induced neoplasm is low but not zero. Thus, long-term surveillance imaging is advised for patients treated with SRS.

Conventional spindle cell-type malignant peripheral nerve sheath tumor arising in a sporadic schwannoma

Malignant peripheral nerve sheath tumor is a malignant tumor showing nerve sheath differentiation. Approximately one-half of malignant peripheral nerve sheath tumors arise from a benign peripheral nerve sheath tumor, which is commonly a neurofibroma in patients with neurofibromatosis type 1. Malignant peripheral nerve sheath tumor arising in a sporadic schwannoma of soft tissue is extremely rare. In this condition, malignant cells usually show epithelioid morphology, meeting the diagnostic criteria for epithelioid malignant peripheral nerve sheath tumor. Here, we present an extraordinary case of spindle cell-type malignant peripheral nerve sheath tumor arising in a schwannoma on the back of a 58-year-old woman without neurofibromatosis. The malignant component showed hypercellular spindle cell proliferation with high mitotic activities; in contrast, the benign component showed hypocellular spindle cell proliferation in a palisading pattern and with Verocay bodies. Immunohistochemical S-100 protein staining showed a clear contrast between the malignant (negative) and benign (positive) components, which was useful for differentiating cellular schwannoma. Recognizing this rare condition is helpful in the pathologic diagnosis of schwannoma showing cellular proliferation in part.

Malignant Peripheral Nerve Sheath Tumour: CT and MRI Findings

Malignant peripheral nerve sheath tumour (MPNST) is extremely rare malignancy in the general population, occurring more frequently in patients with Neurofibromatosis type 1 (NF1). In the literature five cases of MPNST arising from the parapharyngeal space (PPS) in patients without neurofibromatosis have been reported. We report imaging techniques in a patient with MPNST in the PPS, who had neither a family history nor sign of NF1. Computed tomography (CT) scan and magnetic resonance imaging (MRI) were performed for a correct therapeutic planning. CT and MRI findings were correlated with hystopathological diagnosis.

Updates on the diagnosis and treatment of intracranial nerve malignant peripheral nerve sheath tumors

Background:

Malignant peripheral nerve sheath tumors (MPNSTs) are rare entities and MPNSTs of intracranial nerves are even more sporadic. MPNSTs present diagnosis and treatment challenges since there are no defined diagnosis criteria and no established therapeutic strategies.

Methods:

We reviewed literature for MPNST-related articles. We found 45 relevant studies in which 60 cases were described.

Results:

We identified 60 cases of intracranial nerve MPNSTs. The age ranged from 3 to 75 years old. Male to female ratio was 1.5:1. The most involved cranial nerves (CNs) were CN VIII (60%), CN V (27%), and CN VII (10%). Most of the MPNSTs reported (47%) arose sporadically, 40% arose from a schwannoma, 8% arose from a neurofibroma, and 6% arose from an unspecified nerve tumor. Twenty patients had a history of radiation exposure, four patients had neurofibromatosis type 1 (NF1), four patients had neurofibromatosis type 2 (NF2), and NF2 was suspected in two other patients. Twenty-two patients were treated with radiotherapy and presented a higher survival rate. Seventy-two percent of patients died of their disease while 28% of patients survived. One-year survival rate was 33%. Forty-five percent of tumors recurred and 19% of patients had metastases.

Conclusion:

MPNSTs involving CNs are very rare. Diagnosis is made in regards to the histological and pathological findings. Imaging may help orient the diagnosis. A preexisting knowledge of the clinical situation is more likely to lead to a correct diagnosis. The mainstay of treatment is radical surgical resection with adjuvant radiotherapy. Since these tumors are associated with a poor prognosis, a close follow-up is mandatory.

Radiation-induced peripheral malignant nerve sheath tumor arising from vestibular schwannoma after linac-based stereotactic radiation therapy: a case report and review of literatures

In recent years the use of stereotactic radiation for vestibular schwannomas has increased worldwide. However, malignant transformation associated with radiation, although uncommon, has been reported in recent publications. We present a case of the 34 year-old female who had left vestibular schwannoma and who underwent surgery and postoperative stereotactic radiotherapy (SRT), hypofraction in 2005. At 6 years after SRT, the patient came with left facial palsy and severe headache. CT brain revealed progression in size with cystic and hemorrhagic changes of the preexisting tumor at left CPA with new obstructive hydrocephalus. Partial tumor removal was done, and the pathological report was malignant peripheral nerve sheath tumor (MPNST). Regarding the uncertainty of carcinogenesis risk, we should still practice radiation therapy with caution, especially in the young patient with tumor predisposition syndrome. Because of low incidence of MPNST after radiation, it should not be a major decision about giving radiotherapy. However, with the poor prognosis of MPNST, this possibility should be explained to the patient before radiation treatment option.

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.

Intrapulmonary schwannoma in the right middle lobe: a case report

Herein, we report a patient with a rare disease, intrapulmonary schwannoma. The patient was a 61-year-old woman who had a 20 mm × 18 mm nodule, with a clear boundary and homogeneous content, on the central side of S4 in the right lung on chest CT. On PET with 18- fluorodeoxyglucose scanning, 18-fluorodeoxyglucose accumulations with a maximal standardized uptake value of 2.5 and 3.3 were observed in the early and late phases, respectively, suggesting a malignant tumor. A thoracoscopic right middle lobectomy was performed because the tumor was present in the segmental bronchial region of the middle lobe. Intrapulmonary schwannoma accounts for 0.2% of lung tumor cases, and cases involving patients who have undergone preoperative PET with 18- fluorodeoxyglucose scanning have rarely been reported.

The molecular biology and novel treatments of vestibular schwannomas

Vestibular schwannomas are histopathologically benign tumors arising from the Schwann cell sheath surrounding the vestibular branch of cranial nerve VIII and are related to the NF2 gene and its product merlin. Merlin acts as a tumor suppressor and as a mediator of contact inhibition. Thus, deficiencies in both NF2 genes lead to vestibular schwannoma development. Recently, there have been major advances in our knowledge of the molecular biology of vestibular schwannomas as well as the development of novel therapies for its treatment. In this article the authors comprehensively review the recent advances in the molecular biology and characterization of vestibular schwannomas as well as the development of modern treatments for vestibular schwannoma. For instance, merlin is involved with a number of receptors including the CD44 receptor, EGFR, and signaling pathways, such as the Ras/raf pathway and the canonical Wnt pathway. Recently, merlin was also shown to interact in the nucleus with E3 ubiquitin ligase CRL4(DCAF1). A greater understanding of the molecular mechanisms behind vestibular schwannoma tumorigenesis has begun to yield novel therapies. Some authors have shown that Avastin induces regression of progressive schwannomas by over 40% and improves hearing. An inhibitor of VEGF synthesis, PTC299, is currently in Phase II trials as a potential agent to treat vestibular schwannoma. Furthermore, in vitro studies have shown that trastuzumab (an ERBB2 inhibitor) reduces vestibular schwannoma cell proliferation. With further research it may be possible to significantly reduce morbidity and mortality rates by decreasing tumor burden, tumor volume, hearing loss, and cranial nerve deficits seen in vestibular schwannomas.

A case of high-grade undifferentiated sarcoma after surgical resection and stereotactic radiosurgery of a vestibular schwannoma

Stereotactic radiosurgery has become a more frequently used treatment modality for vestibular schwannomas; a few reports of malignant transformation and/or radiation-associated tumors have surfaced. The majority of these reported cases were in patients with underlying neurofibromatosis. The authors report a case of a 74-year-old man with rapid progression of a cerebellar-pontine angle tumor 14 years after surgical resection of a vestibular schwannoma (VS) from the same site, and 6 years after stereotactic radiosurgery. A pathological study of the recent tumor showed a high-grade spindle cell neoplasm that bore no resemblance to the initial schwannoma. The patient had no diagnosis of neurofibromatosis. Secondary malignancy occurred in a non-neurofibromatosis patient 6 years after stereotactic radiosurgery. It is our belief that documentation of such cases will provide important evidence that helps evaluate the long-term effect of radiosurgery for VS. Such observations can influence clinical decisions regarding the choice of treatment modalities.

Malignant transformation of acoustic neuroma/vestibular schwannoma 10 years after gamma knife stereotactic radiosurgery

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.

Malignant peripheral nerve sheath tumor arising from benign vestibular schwannoma treated by gamma knife radiosurgery after two previous surgeries: a case report with surgical and pathological observations

BACKGROUND

Gamma knife radiosurgery (GKRS) is an effective treatment for vestibular schwannomas with lower morbidity and mortality. However, malignant transformation associated with GKRS, although uncommon, has been reported in recent publications.

METHODS

We describe a case presenting with malignant peripheral nerve sheath tumor (MPNST) at 8 years after GKRS after incomplete resections.

RESULTS

The tumor appeared to be a typical benign schwannoma at the surgery preceding GKRS, and rapidly enlarged after long-term control, causing progressive neurological deterioration. Operative findings showed that the tumor was composed of two different components, and histopathology distinctively demonstrated MPNST and benign schwannoma.

CONCLUSIONS

The coexistence of benign and malignant components might indicate that the present MPNST had arisen from the benign schwannoma by transformation in association with GKRS.

Malignant peripheral nerve sheath tumor of intracranial nerve: a case series review

OBJECTIVES

The incidence of malignant peripheral nerve sheath tumor (MPNST) is approximately 0.001%. Those involving intracranial nerves are even more exceptional. Little information is available concerning work up and management. Our objective is: (1) to review all cases of intracranial MPNST described in the literature, (2) to highlight the suspicion of intracranial MPNST, (3) to identify the gross pathology, the histopathology, the immunohistochemistry, (4) to discuss the differential diagnosis, the treatment, the recurrence rate, the follow-up, the incidence of metastasis and the prognosis.

METHODS

We reviewed English, Spanish and French literature published from 1950 to date. We used the following Keywords: "malignant peripheral nerve sheath tumor", "cranial nerve", "neurosarcoma", "malignant schwannoma", "neurofibroma", "malignant neurofibroma" and "nerve tumor". We considered cases where MPNST involved an intracranial cranial nerve. The results yielded 20 relevant studies, in which 31 patient's records were transcribed. We also added our case to this series.

RESULTS

We identified 32 cases of cranial MPNST including our case. The age ranged from 5 to 75 years old with most patients being in the 5th and 6th decade. Male to female ratio is 2.5:1. Most cases are developed sporadically (50%), 31% arise from a malignant transformation of schwannoma and 19% from a neurofibroma. Imaging findings were not specific. The cranial nerve VIII is the most involved (15/32), followed by the Vth (10/32) and the VIIth (5/32). 4 cases had neurofibromatosis type 1 and 2 had neurofibromatosis type 2. MPNST will strongly express protein S-100 and collagen IV-laminin. 13 cases were treated with radiotherapy for tumor recurrence and metastasis. In these cases the survival rate was better than the cases without radiotherapy. Fatal outcome occurred in 66% of patients whereas 19% were reported alive with or without complications. The seven cases reported to have metastasis were entirely to the spine. The mean time of recurrence or metastasis is 12.2 months.

CONCLUSION

MPNST of cranial nerves are very rare. In neurofibroma, even though MPNST is mainly associated to type 1, we should keep in mind its association to NF2. Mainstay of treatment is radical resection with adjuvant radiotherapy. Inaccessibility of cranial MPNST may explain the subtotal resection and thus the poor prognosis. Metastasis to the spinal cord is the most frequent one. A close postoperative follow-up is mandatory to eliminate recurrence.

Malignant peripheral nerve sheath tumors of cranial nerves and intracranial contents: a clinicopathologic study of 17 cases

Malignant peripheral nerve sheath tumors (MPNSTs) arising from cranial nerves or their branches are very uncommon. The literature consists mainly of isolated case reports and small series. We identified 17 such cases in 14 males and 3 females. With one exception, the tumors affected adults (age range 5 to 69 y, mean 39, median 32). Sites of involvement included vestibular nerves (n=6), vagal nerves (n=4), facial nerves (n=3) (1 centered in the geniculate ganglion), and 2 unspecified cranial nerves in the posterior fossa. In addition, 1 tumor involved the optic chiasm (n=1). Only 1 tumor arose in brain parenchyma of (frontal lobe). All but 3 lesions were intracranial. Five tumors arose in patients who satisfied clinical criteria for neurofibromatosis type 1 (NF1). One patient with a vestibular tumor and presumed NF2 had previously undergone resection of a contralateral vestibular cellular schwannoma. One posterior fossa tumor was a malignant melanotic schwannoma. Four patients had postirradiation malignant peripheral nerve sheath tumors, 2 having been treated for optic chiasm glioma, both being NF1 affected. One patient was irradiated for hypothalamic pilocytic astrocytoma and another for cervical Hodgkin disease. Identifiable precursor lesions included schwannoma (n=4), plexiform neurofibroma (n=2), and solitary intraneural neurofibroma (n=2). All tumors were histologically high grade (6 grade III and 10 grade IV). Three tumors showed heterologous elements, 2 osseous, and 1 rhabdomyoblastic. More often scattered than diffuse, S-100 protein staining was noted in 11 of 16 tumors and variable collagen IV staining in 10 of the 16. Immunoreactivity for p53 protein was diffuse and strong in 7 of 11 tumors. Twelve patients died within 17 months to 3 years of diagnosis, 1 was lost to follow-up, 2 are very recent cases, and 2 patients are currently alive, 1 after 2 recurrences, and another with spinal leptomeningeal metastases. Malignant cranial nerve sheath tumors are rare and are associated with the same poor prognosis as those of spinal nerves at other sites.

The ErbB inhibitors trastuzumab and erlotinib inhibit growth of vestibular schwannoma xenografts in nude mice: a preliminary study

OBJECTIVE

To analyze the ability of ErbB inhibitors to reduce the growth of vestibular schwannoma (VS) xenografts.

METHODS

Vestibular schwannoma xenografts were established in the interscapular fat pad in nude mice for 4 weeks. Initially, a small cohort of animals was treated with the ErbB2 inhibitor trastuzumab or saline for 2 weeks. Animals also received bromodeoxyuridine injections to label proliferating cells. In a longer-term experiment, animals were randomized to receive trastuzumab, erlotinib (an ErbB kinase inhibitor), or placebo for 12 weeks. Tumor growth was monitored by magnetic resonance imaging during the treatment period. Cell death was analyzed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin end labeling of fragmented DNA.

RESULTS

Tumors can be distinguished with T2-weighted magnetic resonance imaging sequences. Trastuzumab significantly reduced the proliferation of VS cells compared with control (p < 0.01) as analyzed by bromodeoxyuridine uptake. Control tumors demonstrated slight growth during the 12-week treatment period. Both trastuzumab and erlotinib significantly reduced the growth of VS xenografts (p < 0.05). Erlotinib, but not trastuzumab, resulted in a significant increase in the percentage of terminal deoxynucleotidyl transferase-mediated dUTP-biotin end labeling of fragmented DNA-positive VS cells (p < 0.01).

CONCLUSION

In this preliminary study, the ErbB inhibitors trastuzumab and erlotinib decreased growth of VS xenografts in nude mice, raising the possibility of using ErbB inhibitors in the management of patients with schwannomas, particularly those with neurofibromatosis Type 2.

A true malignant schwannoma of the eighth cranial nerve: case report

OBJECTIVE

The clinical presentation, pathology, treatment, and outcome of a 43-year-old woman with a malignant peripheral nerve sheath tumor arising from a benign schwannoma of the eighth cranial nerve are presented.

CLINICAL PRESENTATION

Initially, the tumor was debulked. After finding malignant areas within the benign tumor, it was considered to be a malignant transformation of a previously benign tumor.

INTERVENTION

Aggressive total resection was obtained during a second-stage procedure. Postoperatively, the tumor bed was radiated for palliation.

CONCLUSION

Despite surgery, radiation, and chemotherapy, the patient died rapidly as a result of disseminated metastatic disease.

Glioblastoma multiforme after stereotactic radiotherapy for acoustic neuroma: case report and review of the literature

Indications for the use of radiotherapy in the management of a variety of benign intracranial neoplastic and nonneoplastic pathologies are increasing. Although the short-term risks are minimal, the long-term risks of radiation-induced de novo secondary neoplasms or malignant progression of the primary benign tumor need to be considered. There are currently 19 reported cases of tumors linked with stereotactic radiotherapy/radiosurgery, to which we add our second institutional experience of a patient who succumbed to a glioblastoma multiforme (GBM) after stereotactic radiotherapy for an acoustic neuroma (AN). Review of these 20 cases revealed 10 de novo secondary tumors, of which eight were malignant, with six being malignant gliomas. The majority of the cases (14 of 20) involved AN, with most being in patients with neurofibromatosis-2 (NF2; 8 of 14), reflecting the large numbers and long-term use of radiotherapy for AN. Accelerated growth of the primary benign AN, some 2 to 6 years after focused radiotherapy, was found in six of eight NF2 patients, with pathological verification of a malignant nerve sheath tumor documented in most. The exact carcinogenic risk after radiotherapy is unknown but likely extremely low. However, the risk is not zero and requires discussion with the patient, with specific consideration in young patients and those with a cancer predisposition.

Sporadic malignant nerve sheath tumour of the oculomotor nerve

Malignant peripheral nerve sheath tumours (MPNST) are exceedingly rare in an intracranial location. In this report clinical and pathological evidence for the diagnosis of a MPNST arising from of the oclumotor nerve is presented. To our knowledge this is the first such case reported in the medical literature.

Intrasellar malignant peripheral nerve sheath tumor (MPNST)

Intracranial malignant peripheral nerve sheath tumors (MPNST) and intrasellar schwannomas are rare tumors. We describe a case of an intrasellar schwannoma with progression to a MPNST, a finding that, although very rare, extends the differential diagnosis of intrasellar lesions.

Cellular Neurofibroma with Atypia Mimics Sarcoma: Report of a Case with Immunohistochemical Staining Pattern Analysis and Literature Review

A case of two sporadic cellular neurofibromas with atypia and one widespread hyalinization neurofibroma of the lumbar spine in a 51-year-old man without evidence of neurofibromatosis-1 is reported. Cellular neurofibroma with atypia is an unusual variant. The definite criteria for low-grade and high-grade malignant peripheral nerve sheath tumors as well as cellular neurofibroma are not well defined in the literature. The clinical significance of atypical cellular neurofibroma has rarely been systematically studied. To our knowledge, the concomitance of cellular architecture and cytologic atypia is rarely documented, and this is a rare report of atypical cellular neurofibroma. The recognition of this entity is of great importance to both pathologists and clinicians because atypical cellular neurofibroma is clever at masquerading both histologically and cytologically as a sarcoma; therefore, a precise diagnosis of this variant is essential because of the differences in treatment and clinical behavior between benignancy and malignancy. We also examined the immunohistochemical characteristics of CD34 positive cells and focal high expression of p53 up to 73% encountered in our case. To our knowledge, seldom have series or case reports elucidated this phenomenon.

Twenty years' experience in the treatment of acoustic neuromas with fractionated radiotherapy: a review of 45 cases

PURPOSE

To evaluate very long-term results of fractionated radiotherapy (FRT) of acoustic neuromas (AN).

METHODS AND MATERIALS

From January 1986 to January 2004, FRT was performed in 45 consecutive patients (46 AN). Indications were as follows: poor general condition contraindicating surgery, hearing preservation in bilateral neuromas, partial resection, nonsurgical recurrence. A 3-field to 5-field technique with static beams was used. A mean total dose of 51 Gy was given (1.80 Gy/fraction). The median tumor diameter was 31 mm (range, 11-55 mm). The median follow-up from FRT was 80 months (range, 4-227 months).

RESULTS

The particularity of our series consists of a very long-term follow-up of FRT given to selected patients. Nineteen patients died, two with progressive disease, and 17 from non-AN causes. A serviceable level of hearing was preserved in 7/9 hearing patients. No patient had facial or trigeminal neuropathy. Tumor shrinkage was observed in 27 (59%) and stable disease in 16 (35%). Tumor progression occurred in three patients, 12 to 15 months after FRT. Two additional tumors recurred after shrinkage 20 and 216 months after treatment and were operated on. Actuarial local tumor control rates at 5 and 15 years were 86%. For the patient who had a tumor recurrence at 216 months, histologic examination documented transformation to a low-grade malignant peripheral nerve sheath tumor.

CONCLUSION

Very long-term efficacy of FRT is well documented in this series. However, our results suggest that malignant transformation can occur many years after FRT so we advocate caution when using this treatment for young patients.

Malignant transformation and new primary tumours after therapeutic radiation for benign disease: substantial risks in certain tumour prone syndromes

In recent years the use of radiation treatment for benign tumours has increased with the advent of stereotactic delivery and, in particular, single high dose gamma knife therapy. This has been particularly true for benign CNS (central nervous system) tumours such as vestibular schwannoma, meningioma, pituitary adenoma, and haemangioblastoma. While short term follow up in patients with isolated tumours suggests this treatment is safe, there are particular concerns regarding its use in childhood and in tumour predisposing syndromes. We have reviewed the use of radiation treatment in these contexts with particular regard to malignant transformation and new tumour induction. This review indicates that much more caution is warranted regarding the use of radiation treatment for benign tumours in childhood and in tumour prone conditions such as the neurofibromatoses.

Current management of head and neck schwannomas

PURPOSE OF REVIEW

The purpose of this review is to discuss the contemporary management of head and neck schwannomas by reviewing the literature and presenting the authors' experience.

RECENT FINDINGS

Molecular studies are attempting to link genetic factors to the development of nerve sheath tumors. Many studies emphasize the importance of preserving the nerve of origin, but structural preservation may not necessarily lead to the preservation of its functional integrity. The importance of neural reconstruction and postoperative rehabilitation is also emphasized.

SUMMARY

Head and neck schwannomas are uncommon tumors that may affect any peripheral, cranial, or autonomic nerve. This explains their variation in terms of location, clinical presentation, and outcome after surgical resection. History, physical examination, fine needle aspiration, and magnetic resonance imaging are used as diagnostic modalities. Cure entails a complete resection, all attempts being made to preserve the nerve of origin. Otherwise, immediate reconstruction and postoperative rehabilitation should be undertaken in the context of a multidisciplinary management team.