BRAF V600E, TERT, and IDH2 Mutations in Pleomorphic Xanthoastrocytoma: Observations from a Large Case-Series Study

Noninvasive prediction of BRAF V600E mutation status of pleomorphic xanthoastrocytomas with MRI morphologic features and diffusion-weighted imaging

OBJECTIVES

Seeking a noninvasive predictor for BRAF V600E mutation status of pleomorphic xanthoastrocytomas (PXAs) is essential for their prognoses and therapeutic use of BRAF inhibitors. We aimed to noninvasively diagnose BRAF V600E-mutated PXAs using MRI morphologic, DWI and clinical parameters.

METHODS

The clinical findings, anatomical MRI characteristics, and diffusion parameters of 36 pathologically confirmed PXAs were retrospectively analyzed, and BRAF V600E-mutated (n = 16) and wild-type (n = 20) groups were compared. A binary logistic-regression analysis was performed, and a ROC curve was calculated to determine the independent predictors of BRAF V600E mutation status, diagnostic accuracy, and optimal cut-off value.

RESULTS

A comparison of findings between groups showed that BRAF V600E-mutated PXAs were more frequent in children and young adults (≤ 35 years; P = 0.042) who often had histories of seizures (P = 0.004). Furthermore, BRAF V600E-mutated PXAs generally presented as solitary masses (P = 0.024), superficial locations with meningeal attachment (P < 0.001), predominantly cystic with mural nodules (P = 0.005), and had greater minimal ADC ratio (ADCratio) values of the tumor and peritumoral edema (P < 0.001). Binary logistic regression showed that age ≤ 35 years, solitary mass, superficial locations with meningeal attachment, and a greater minimal ADCratio of the tumor were independent predictors of BRAF V600E-mutated PXAs. The combination of all four independent predictors resulted in the highest sensitivity (100%) and specificity (90%), with AUC = 0.984.

CONCLUSION

The BRAF V600E mutation status of PXAs could be noninvasively predicted using clinical and MRI characteristics.

CRITICAL RELEVANCE STATEMENT

The noninvasive diagnostic criteria for BRAF V600E-mutated PXAs could offer guidance for the administration of BRAF V600E mutation inhibitors in the future.

Exploring prognostic factors and treatment strategies for long-term survival in pleomorphic xanthoastrocytoma patients

Pleomorphic xanthoastrocytomas (PXA) are rare, accounting for < 1% of all astrocytomas. Literature on the clinical course and treatment outcomes of PXAs is limited. The study aimed to determine prognosis and treatment strategies for PXAs. Patients who had PXAs surgery between 2000-2021 were retrospectively analyzed for demographics and radiological characteristics. Initial and salvage treatment outcomes were recorded. Overall, 40 and 9 patients had grade 2 and 3 PXAs; their 5-year progression-free survival (PFS) rates were 75.8% and 37.0%, respectively (p = 0.003). Univariate analysis revealed that strong T1 enhancement (p = 0.036), infiltrative tumor margins (p < 0.001), peritumoral edema (p = 0.003), WHO grade (p = 0.005), and gross total resection (p = 0.005) affected the PFS. Multivariate analysis revealed that the WHO grade (p = 0.010) and infiltrative tumor margins (p = 0.008) influenced the PFS. The WHO grade (p = 0.027) and infiltrative tumor margins (p = 0.027) also affected the overall survival (OS). Subgroup analysis for grade 2 PXAs revealed no significant associations between adjuvant radiation therapy and the PFS and OS. This study highlighted the heterogeneous nature of PXAs and its impact on patient prognosis. Infiltrative tumor margins emerged as a key prognostic factor. Our findings have emphasized the prognostic relevance of radiological features and the need for larger studies on comprehensive management.

Clinical, Morphological, and Molecular Study on Grade 2 and 3 Pleomorphic Xanthoastrocytoma

PURPOSE

Pleomorphic xanthoastrocytoma (PXA) is an uncommon astrocytoma that tends to occur in children and young adults and has a relatively favorable prognosis. The 2021 WHO classification of tumors of the central nervous system (CNS WHO), 5th edition, rates PXAs as grade 2 and grade 3. The histological grading was based on mitotic activity (≥2.5 mitoses/mm2). This study specifically evaluates the clinical, morphological, and, especially, the molecular characteristics of grade 2 and 3 PXAs.

METHODS

Between 2003 and 2021, we characterized 53 tumors with histologically defined grade 2 PXA (n = 36, 68%) and grade 3 PXA (n = 17, 32%).

RESULTS

Compared with grade 2 PXA, grade 3 PXA has a deeper location and no superiority in the temporal lobe and is more likely to be accompanied by peritumoral edema. In histomorphology, epithelioid cells and necrosis were more likely to occur in grade 3 PXA. Molecular analysis found that the TERT promoter mutation was more prevalent in grade 3 PXA than in grade 2 PXA (35% vs. 3%; p = 0.0005) and all mutation sites were C228T. The cases without BRAF V600E mutation or with necrosis in grade 3 PXA had a poor prognosis (p = 0.01).

CONCLUSION

These data define PXA as a heterogeneous astrocytoma. Grade 2 and grade 3 PXAs have different clinical and histological characteristics as well as distinct molecular profiles. TERT promoter mutations may be a significant genetic event associated with anaplastic progression. Necrosis and BRAF V600E mutation play an important role in the prognosis of grade 3 PXA.

Anaplastic ganglioglioma - a diagnosis comprising several distinct tumour types

Anaplastic ganglioglioma is a rare tumour and diagnosis has been based on histological criteria. The 5^th edition of the World Health Organization Classification of Tumours of the Central Nervous System (CNS WHO) does not list anaplastic ganglioglioma as a distinct diagnosis due to lack of molecular data in previous publications AIM: We retrospectively compiled a cohort of 54 histologically diagnosed anaplastic gangliogliomas to explore whether the molecular profiles of these tumours represent a separate type or resolve into other entities METHODS: Samples were subjected to histological review, DNA methylation profiling and next generation sequencing. Morphologic and molecular data were summarised to an integrated diagnosis RESULTS: The majority of histologically diagnosed anaplastic gangliogliomas resolved into CNS WHO diagnoses of glial tumours, most commonly pleomorphic xanthoastrocytoma (16/54), glioblastoma, IDH wildtype and diffuse paediatric-type high-grade glioma, H3 wildtype and IDH wildtype (11 and 2/54) followed by low-grade glial or glioneuronal tumours including pilocytic astrocytoma, dysembryoplastic neuroepithelial tumour and diffuse leptomeningeal glioneuronal tumour (5/54), IDH mutant astrocytoma (4/54) and others (6/54). A subset of tumours (10/54) was not assignable to a CNS WHO diagnosis and common molecular profiles pointing to a separate entity were not evident CONCLUSION: In summary, we show that tumours histologically diagnosed as anaplastic ganglioglioma comprise a wide spectrum of CNS WHO tumour types with different prognostic and therapeutic implications. We therefore suggest assigning this designation with caution and recommend comprehensive molecular workup.

Pleomorphic Xanthoastrocytoma: a single institution retrospective analysis and a review of the literature

Background

 Pleomorphic xanthoastrocytoma (PXA) is a rare low-grade brain tumor. To date, limited studies have analyzed factors affecting survival outcomes and defined the therapeutic strategy. The aim of this retrospective analysis was to investigate the clinicopathologic characteristics of PXA and identify factors associated with outcomes.

Methods

 We retrospectively analyzed a cohort of 16 adult and children patients with PXA who underwent primary resection from 1997 to 2019, referred to our Radiation Oncology Unit and to Meyer’s Paediatric Hospital. We also reviewed the relevant literature.

Results

 All patients underwent primary surgical resection; 10 patients received adjuvant radiation treatment course, ranging from DTF 54 to 64 Gy; 8 of them received, in addition, concurrent adjuvant chemotherapy; 6 patients underwent only radiological follow-up. After a median follow up was 60 months: median OS was 34.9 months (95% CI 30–218), 1-year OS 87%, 5-years OS 50%, 10-years OS 50%; median PFS 24.4 months (95% CI 13–156), 1-year PFS 80%, 5-years PFS 33%, 10-years PFS 33%. A chi-square test showed a significant association between OS and recurrent disease (p = 0.002) and with chemotherapy adjuvant treatment (p = 0.049). A borderline statistical significant association was instead recognized with BRAF mutation (p = 0.058).

Conclusions

Despite our analysis did not reveal a strong prognostic or predictive factor able to address pleomorphic xanthoastrocytoma management; however, in selected patients could be considered the addition of adjuvant radiation chemotherapy treatment after adequate neurosurgical primary resection. Furthermore, recurrent disease evidenced a detrimental impact on survival.

Autobiographical Case Report of Experiences With Pleomorphic Xanthoastrocytoma

Pleomorphic xanthoastrocytoma is a rare brain tumor of WHO grade II designation. This case report describes the author's experience with the discovery of the tumor, living with the tumor, and eventual treatment and aftermath of how it affected her life and her understanding of the medical system.

Central Nervous System Tumor Classification: An Update on the Integration of Tumor Genetics

In 2016, the World Health Organization Classification of CNS Tumors introduced molecular abnormalities that refined tumor diagnoses. Around this time, the introduction of large scale genetic mutational analyses quickly advanced our knowledge of recurrent abnormalities in disease. In 2017, the C-IMPACT group was established to render expert consensus opinions regarding the application of molecular findings into central nervous system tumor diagnoses. C-IMPACT have presented their recommendations in 7 peer-reviewed publications; this article details those recommendations that are expected to be incorporated into the upcoming fifth edition of the World Health Organization classification.

Identification of BRAF p. V600E-Mutant and Wild-Type by MR Imaging in Pleomorphic Xanthoastrocytoma and Anaplastic Pleomorphic Xanthoastrocytoma

BACKGROUND AND PURPOSE

Compared with BRAF p. V600E wild-type pleomorphic xanthoastrocytoma, BRAF p. V600E-mutant pleomorphic xanthoastrocytoma showed a higher survival rate. In this study, we focused on finding preoperative MR imaging differences between BRAF p. V600E mutant and wild-type in pleomorphic xanthoastrocytoma and anaplastic pleomorphic xanthoastrocytoma.

MATERIALS AND METHODS

Twenty-three patients with pathologically confirmed pleomorphic xanthoastrocytoma or anaplastic pleomorphic xanthoastrocytoma in our hospital were retrospectively analyzed from January 2015 to December 2020. They were divided into a BRAF p. V600E-mutant group (including 6 pleomorphic xanthoastrocytomas and 5 anaplastic pleomorphic xanthoastrocytomas) and a wild-type group (including 8 pleomorphic xanthoastrocytomas and 4 anaplastic pleomorphic xanthoastrocytomas). The preoperative MR imaging characteristics of these groups were statistically compared.

RESULTS

The wild-type pleomorphic xanthoastrocytoma group presented with more aggressive conventional and advanced MR imaging features than the mutant pleomorphic xanthoastrocytoma group, including greater mean maximum tumor diameter (3.1 [SD, 0.9] cm versus 1.7 [SD, 0.4 ] cm, P < .05), more frequent heterogeneous contrast enhancement of solid portions (100% versus 0%, P < .001), more obvious peritumoral edema (mean, [2.1 SD, 0.7] cm versus 0.6 [SD, 0.2] cm, P < .01), and lower mean minimum relative ADC (896 [SD, 86] versus 988 [SD, 73], P < .05) and mean relative ADC (1060 [SD, 159] versus 1248 [SD, 116], P < .05) on DWI. However, there was no significant difference in either conventional or advanced MR imaging features between the wild-type anaplastic pleomorphic xanthoastrocytoma group and the mutant anaplastic pleomorphic xanthoastrocytoma group.

CONCLUSIONS

Neurosurgeons should carefully interpret MR images before an operation and select appropriate surgical strategies according to genotype prediction.

Differences in treatment patterns and overall survival between grade II and anaplastic pleomorphic xanthoastrocytomas

INTRODUCTION

Pleomorphic xanthoastrocytomas (PXAs) are classified as a grade II neoplasm, typically occur in children, and have favorable prognoses. However, their anaplastic counterparts remain poorly understood and vaguely characterized. In the present study, a large cohort of grade II PXA patients were compared with primary anaplastic PXA (APXA) patients to characterize patterns in treatment and survival.

METHODS

Data were collected from the National Cancer Institute's SEER database. Univariate and multivariate Cox regressions were used to evaluate the prognostic impact of demographic, tumor, and treatment-related covariates. Propensity score matching was used to balance baseline characteristics. Kaplan-Meier curves were used to estimate survival.

RESULTS

A total of 346 grade II PXA and 62 APXA patients were identified in the SEER database between 2000 and 2016. Kaplan-Meier analysis revealed substantially inferior survival for APXA patients compared to grade II PXA patients (median survival: 51 months vs. not reached) (p < 0.0001). After controlling across available covariates, increased age at diagnosis was identified as a negative predictor of survival for both grade II and APXA patients. In multivariate and propensity-matched analyses, extent of resection was not associated with improved outcomes in either cohort.

CONCLUSIONS

Using a large national database, we identified the largest published cohort of APXA patients to date and compared them with their grade II counterparts to identify patterns in treatment and survival. Upon multivariate analysis, we found increased age at diagnosis was inversely associated with survival in both grade II and APXA patients. Receipt of chemoradiotherapy or complete surgical resection was not associated with improved outcomes in the APXA cohort.

Predictors of outcome in pleomorphic xanthoastrocytoma

Background

Pleomorphic xanthoastrocytomas (PXA) are circumscribed gliomas that typically have a favorable prognosis. Limited studies have revealed factors affecting survival outcomes in PXA. Here, we analyzed the largest PXA dataset in the literature and identify factors associated with outcomes.

Methods

Using the Surveillance, Epidemiology, and End Results (SEER) 18 Registries database, we identified histologically confirmed PXA patients between 1994 and 2016. Overall survival (OS) was analyzed using Kaplan-Meier survival and multivariable Cox proportional hazard models.

Results

In total, 470 patients were diagnosed with PXA (males = 53%; median age = 23 years [14-39 years]), the majority were Caucasian (n = 367; 78%). The estimated mean OS was 193 months [95% CI: 179-206]. Multivariate analysis revealed that greater age at diagnosis (≥39 years) (3.78 [2.16-6.59], P < .0001), larger tumor size (≥30 mm) (1.97 [1.05-3.71], P = .034), and postoperative radiotherapy (RT) (2.20 [1.31-3.69], P = .003) were independent predictors of poor OS. Pediatric PXA patients had improved survival outcomes compared to their adult counterparts, in which chemotherapy (CT) was associated with worse OS. Meanwhile, in adults, females and patients with temporal lobe tumors had an improved survival; conversely, tumor size ≥30 mm and postoperative RT were associated with poor OS.

Conclusions

In PXA, older age and larger tumor size at diagnosis are risk factors for poor OS, while pediatric patients have remarkably improved survival. Postoperative RT and CT appear to be ineffective treatment strategies while achieving GTR confer an improved survival in male patients and remains the cornerstone of treatment. These findings can help optimize PXA treatment while minimizing side effects. However, further studies of PXAs with molecular characterization are needed.

Molecular Features and Prognostic Factors of Pleomorphic Xanthoastrocytoma: A Collaborative Investigation of the Tohoku Brain Tumor Study Group

Pleomorphic xanthoastrocytoma (PXA) is a rare glial tumor, however, its histological differentiation from high-grade gliomas is often difficult. Molecular characteristics may contribute to a better diagnostic discrimination. Prognostic factors of PXA are also important but few relevant reports have been published. This study investigated the molecular features and prognostic factors of PXAs. Seven university hospitals participated in this study by providing retrospective clinical data and tumor samples of PXA cases between 1993 and 2014. Tumor samples were analyzed for immunohistochemical (IHC) neuronal and glial markers along with Ki67. The status of the BRAF and TERT promoter (TERTp) mutation was also evaluated using the same samples, followed by feature extraction of PXA and survival analyses. In all, 19 primary cases (17 PXA and 2 anaplastic PXA) were included. IHC examination revealed the stable staining of nestin and the close association of synaptophysin to NFP. Of the PXA cases, 57% had the BRAF mutation and only 7% had the TERTp mutation. On univariate analysis, age (≥60 years), preoperative Karnofsky performance status (KPS) (≤80%), and marked peritumoral edema were significantly associated with progression-free survival (PFS). No independent factor was indicated by the multivariate analysis. In conclusion, PXA was characterized by positive nestin staining and a few TERTp mutations. The neuronal differential marker and BRAF status may help in diagnosis. Patient age, preoperative KPS, and marked perifocal edema were associated with PFS. The present study is limited because of small number of cases and its retrospective nature. Further clinical study is needed.

BRAF Alteration in Central and Peripheral Nervous System Tumors

BRAF (alternately referred to as v-raf murine sarcoma viral oncogene homolog B1) is a proto-oncogene involved in the mitogen-activated protein kinase (MAPK) pathway. BRAF alterations are most commonly missense mutations or aberrant fusions. These mutations are observed in numerous primary central nervous system tumors as well as metastases. This review discusses the prevalence of BRAF alteration within select notable CNS tumors, and their prognostic associations. Included are some novel entities such as diffuse leptomeningeal glioneuronal tumor (DLGNT), polymorphous low grade neuroepithelial tumor of the young (PLNTY), and multinodular and vacuolating neuronal tumor (MVNT). Knowledge of this gene’s integrity in CNS and PNS tumors can have profound diagnostic and therapeutic implications. Also reviewed are the current state of targeted therapy against aberrant BRAF as it pertains mostly to the CNS and to a lesser extent in PNS, and certain diagnostic aspects.

Pleomorphic Xanthoastrocytoma of the Pineal Region in a Pediatric Patient With Neurofibromatosis Type 1

Background: Pleomorphic xanthoastrocytoma (PXA) is a rare and often focal glioma that most commonly affects children and young adults. Lesions are preferentially supratentorial and superficial, although infratentorial masses have been described, along with occasional involvement of the leptomeninges. The World Health Organization (WHO) categorizes these tumors as grade II, with surgical resection carrying a favorable prognosis. However, these tumors may undergo malignant degeneration and must be identified for appropriate treatment and prognosis. PXA has been associated with neurofibromatosis type 1 (NF1), although it is not the classic phenotype of NF1. We present a novel report of PXA, atypically located in the pineal region of a patient with a history of NF1.

Case Report: A 17-year-old male with a history of NF1 presented with 1 month of bifrontal headaches. Magnetic resonance imaging was significant for a heterogeneous tectal mass, suspicious for a glioma extending to the fourth ventricle and causing displacement of the cerebral aqueduct without obstructive hydrocephalus. Following an infratentorial-supracerebellar approach for tumor resection, histopathology confirmed a low-grade variable neoplasm consistent with PXA. Postoperative imaging confirmed gross total resection with no evidence of recurrence at 9 months postoperatively.

Conclusion: To our knowledge, this case is the fifth report of pineal PXA and the first associated with NF1. Because PXA presents similarly to other NF1-related intracranial tumors, careful diagnosis via immunohistochemistry is imperative. Gross tumor resection is usually curative; however, PXA has the propensity to undergo malignant degeneration and may require adjuvant treatment.

TERT expression is susceptible to BRAF and ETS-factor inhibition in BRAFV600E/TERT promoter double-mutated glioma

The BRAF gene and the TERT promoter are among the most frequently altered genomic loci in low-grade (LGG) and high-grade-glioma (HGG), respectively. The coexistence of BRAF and TERT promoter aberrations characterizes a subset of aggressive glioma. Therefore, we investigated interactions between those alterations in malignant glioma. We analyzed co-occurrence of BRAFV600E and TERT promoter mutations in our clinical data (n = 8) in addition to published datasets (n = 103) and established a BRAFV600E-positive glioma cell panel (n = 9) for in vitro analyses. We investigated altered gene expression, signaling events and TERT promoter activity upon BRAF- and E-twenty-six (ETS)-factor inhibition by qRT-PCR, chromatin immunoprecipitation (ChIP), Western blots and luciferase reporter assays. TERT promoter mutations were significantly enriched in BRAFV600E-mutated HGG as compared to BRAFV600E-mutated LGG. In vitro, BRAFV600E/TERT promoter double-mutant glioma cells showed exceptional sensitivity towards BRAF-targeting agents. Remarkably, BRAF-inhibition attenuated TERT expression and TERT promoter activity exclusively in double-mutant models, while TERT expression was undetectable in BRAFV600E-only cells. Various ETS-factors were broadly expressed, however, only ETS1 expression and phosphorylation were consistently downregulated following BRAF-inhibition. Knock-down experiments and ChIP corroborated the notion of a functional role for ETS1 and, accordingly, all double-mutant tumor cells were highly sensitive towards the ETS-factor inhibitor YK-4-279. In conclusion, our data suggest that concomitant BRAFV600E and TERT promoter mutations synergistically support cancer cell proliferation and immortalization. ETS1 links these two driver alterations functionally and may represent a promising therapeutic target in this aggressive glioma subgroup.

Pathologic and molecular aspects of anaplasia in circumscribed gliomas and glioneuronal tumors

Many breakthroughs have been made in the past decade regarding our knowledge of the biological basis of the diffuse gliomas, the most common primary central nervous system (CNS) tumors. These tumors as a group are aggressive, associated with high mortality, and have a predilection for adults. However, a subset of CNS glial and glioneuronal tumors are characterized by a more circumscribed pattern of growth and occur more commonly in children and young adults. They tend to be indolent, but our understanding of anaplastic changes in these tumors continues to improve as diagnostic classifications evolve in the era of molecular pathology and more integrated and easily accessible clinical databases. The presence of anaplasia in pleomorphic xanthoastrocytomas and gangliogliomas is assigned a WHO grade III under the current classification, while the significance of anaplasia in pilocytic astrocytomas remains controversial. Recent data highlight the association of the latter with aggressive clinical behavior, as well as the presence of molecular genetic features of both pilocytic and diffuse gliomas, with the recognition that the precise terminology remains to be defined. We review the current concepts and advances regarding histopathology and molecular understanding of pilocytic astrocytomas, pleomorphic xanthoastrocytomas, and gangliogliomas, with a focus on their anaplastic counterparts.