Anaplastic PXA in adults: case series with clinicopathologic and molecular features

Extra-temporal pediatric low-grade gliomas and epilepsy

Low-grade gliomas, especially glioneuronal tumors, are a common cause of epilepsy in children. Seizures associated with low-grade pediatric tumors are medically refractory and present a significant burden to patients. Often, morbidity and patients´ quality of life are determined rather by the control of seizures than the oncological process itself and the resolution of epilepsy represents an important part in the treatment of LGGs. The pathogenesis of tumor-related seizures in focal LGG tumors is multifactorial, and mechanisms differ probably among patients and tumor types. Pediatric low-grade tumors associated with epilepsy include a series of neoplasms that have a pure astrocytic or glioneuronal lineage. They are usually benign tumors with a neocortical localization typically in the temporal lobes, but also in other supratentorial locations. Gangliogliomas and dysembryoplastic neuroepithelial tumors (DNET) are the most common entities together with astrocytic gliomas (pilocytic astrocytomas and pleomorphic xanthoastrocytoma) and angiocentric gliomas, and dual pathology is found in up to 40% of glioneuronal tumors. The treatment of low-grade gliomas and associated epilepsy is based mainly on resection and the extent of surgery is the main predictor of postoperative seizure control in patients with a LGG. Long-term epilepsy-associated tumors (LEATs) tend to be well-circumscribed, and therefore, the chances for a complete resection and epilepsy control with a safe approach are very high. New treatments have emerged as alternatives to open microsurgical approaches, including laser thermal ablation or the use of BRAF inhibitors. Future advances in identifying seizure-related biomarkers and molecular tumor pathways will facilitate targeted treatment strategies that will have a deep impact both in oncologic and epilepsy outcomes.

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.

Impact of Grade on Survival in Pleomorphic Xanthoastrocytoma and Low Prevalence of BRAF V600E Mutation

BACKGROUND

The prevalence of BRAFV600E mutations in pleomorphic xanthoastrocytoma (PXA) World Health Organization (WHO) Grade 2 and PXA WHO Grade 3 reported varies from 60% to 80%, yet the prognostic implications remain unclear.

METHODS

We reviewed the demographic and clinicoradiologic data of 20 PXAs WHO Grade 2 and 13 PXAs WHO Grade 3, operated between 2007 and 2020, to ascertain extent of excision, recurrence, progression-free survival (PFS), and overall survival (OS). PXAs WHO Grade 3 were defined by the presence of >5 mitoses/high-power field. PXAs WHO Grade 3 received adjuvant radiation therapy and chemotherapy whereas PXAs received radiation therapy if subtotally excised. All samples were analyzed for the presence of BRAFV600E mutation using DNA obtained from paraffin blocks using droplet-digital polymerase chain reaction.

RESULTS

The median patient age at diagnosis was 22 years with a male preponderance. BRAFV600E mutations were noted in 30% of tumors; 8 PXAs WHO Grade 2 and 2 PXAs WHO Grade 3. Recurrence occurred in 6 of 13 PXA WHO Grade 3 (55%) and 1 of 20 PXAs WHO Grade 2 (5%). At median follow-up of 45 months, the OS was 54 months and 33 months in the PXA WHO Grade 2 and PXA WHO Grade 3 groups, respectively (P = 0.02). OS and PFS did not differ between BRAF-mutated and BRAF-negative tumors.

CONCLUSIONS

BRAFV600E mutations are less frequent in our population than reported in the literature. The BRAF mutation does not significantly impact OS and PFS. PXAs WHO Grade 3 are a distinct clinical entity, associated with worse PFS and OS than PXAs WHO Grade 2.

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.

A case series of pediatric survivors of anaplastic pleomorphic xanthoastrocytoma

Background

Anaplastic pleomorphic xanthoastrocytoma (APXA) is a rare subtype of CNS astrocytoma. They are generally treated as high-grade gliomas; however, uncertainty exists regarding the optimal therapy. Here, we report on 3 pediatric cases of APXA.

Methods

Our institutional database was queried for cases of APXA and 3 cases were identified. Surgical samples were processed for methylation profiling and chromosomal microarray analysis. Methylation data were uploaded to the online CNS tumor classifier to determine methylation-based diagnoses to determine copy number variations (CNVs).

Results

Two patients were male, 1 female, and all were aged 12 years at diagnosis. All underwent a gross total resection (GTR) and were diagnosed with an APXA. Immunohistochemical analysis demonstrated that 2 cases were BRAF V600E positive. Methylation-based tumor classification supported the APXA diagnosis in all cases. CNV analyses revealed homozygous CKDN2A deletions in all and chromosome 9p loss in 2 cases. All patients received radiation therapy (54 Gy in 30 fractions) with concurrent temozolomide. Two patients received maintenance chemotherapy with temozolomide and lomustine for 6 cycles as per the Children’s Oncology Group ACNS0423. The third patient recurred and went on to receive a second GTR and 6 cycles of lomustine, vincristine, and procarbazine. All are alive with no evidence of disease >4 years post-treatment completion (overall survival = 100%, event free survival = 67%).

Conclusions

The natural history and optimal treatment of this rare pediatric tumor are not well understood. This case series supports the use of adjuvant chemoradiotherapy in the treatment of APXA. The genetic landscape may be informative for optimizing treatment and prognosis.

Anaplastic Pleomorphic Xanthoastrocytoma: A Case Report and Literature Review

Background

With an incidence of less than 1% among astrocytomas, pleomorphic xanthoastrocytoma (PXA) is rare. When its mitotic activity exceeds 5 mitoses/10 high-power fields, PXA is defined as anaplastic pleomorphic xanthoastrocytoma (APXA). This report documents the clinical manifestations and histopathological characteristics of APXA to help prevent future misdiagnoses.

Case Presentation

A 28-year-old male patient had a sudden limb twitch and visited a local hospital. A head magnetic resonance imaging scan showed large patches of abnormal signal intensity that were approximately 6.0×3.3 cm in size in the right frontal and parietal lobes, with iso- to slightly hypointense signals on T1-weighted images (T1WI) and mixed hyperintense signals on T2-weighted images (T2WI). Optical microscopic imaging found pleomorphic tumor cells with sheet-like growth, as well as foamy tumor cells, multinucleated giant cells, pleomorphic cells with atypical nuclei, and acidophilic bodies. Some areas were densely packed with obvious atypia and visible mitoses. The patient tested positive for glial fibrillary acidic protein (GFAP), vimentin (Vim), neuronal nuclear antigen (NeuN), P53, oligodendrocyte transcription factor-2 (OLIG-2), and ATRX, while he tested negative for synaptophysin (Syn), CD34, S-100, BRAF V600E, and IDH1 R132H. The Ki-67 labeling index was 15%. Genetic sequencing showed that IDH1 and IDH2 genes were wild-type, but that his BRAF gene harbored the V600E mutation.

Conclusion

APXA is a WHO grade III astrocytoma that can be distinguished from WHO grade II PXA according to the level of mitosis. Imaging may help to inform the difficult differentiation between APXA and epithelioid glioblastoma. Nonetheless, a clear diagnosis warrants carrying out a comprehensive analysis, including histomorphological, immunophenotypic, and molecular assessments.

Low-grade developmental and epilepsy associated brain tumors: a critical update 2020

Brain tumors represent the second most frequent etiology in patients with focal seizure onset before 18 years of age and submitted to epilepsy surgery. Hence, this category of brain tumors, herein defined as low-grade, developmental, epilepsy-associated brain tumors (LEAT) is different from those frequently encountered in adults as (A): 77% of LEAT occur in the temporal lobe; (B): the vast majority of LEAT are of low malignancy and classified as WHO I°; (C): LEAT are often composed of mixed glial and neuronal cell components and present with variable growth patterns including small cysts or nodules; (D): LEAT do not share common gene driving mutations, such as IDH1 or 1p/19q co-deletions. Characteristic entities comprise the ganglioglioma (GG), the dysembryoplastic neuroepithelial tumor (DNT), the angiocentric glioma (AG), the isomorphic diffuse glioma (IDG) and the papillary glio-neuronal tumor (PGNT), representing 73.2% of 1680 tumors collected in a large German series of 6747 patients submitted to epilepsy surgery. In the realm of exciting discoveries of genetic drivers of brain tumors new genes have been also reported for LEAT. BRAF V600E mutations were linked to GG with CD34 expression, FGFR1 mutations to DNT, MYB alterations to AG and also IDG and PRKCA fusions to PGNT, suggesting the possibility to also develop a genetically driven tumor classification scheme for LEAT. Rare availability of LEAT in a single center is a challenging obstacle, however, to systematically unravel the neurobiological nature and clinical behavior of LEAT. Other challenges in need of clarification include malignant tumor progression of LEAT entities, seizure relapse in patients following bulk tumor resection and the controversial issue of associated focal cortical dysplasia as additional pathomechanism. In order to advance our understanding and promote reliable diagnostic work-up of LEAT, we recommend, therefore, international collaboration to achieve our goals.

Rare clinical presentations of pleomorphic xanthoastrocytoma with a high proliferative index: Two case reports

INTRODUCTION

Pleomorphic xanthoastrocytomas (PXA) are rare, typically benign, slow-growing tumors that commonly occur in the cerebral hemispheres. We describe two cases of clinically aggressive PXA with uncommon locations; one was in the tectal plate, and the other had simultaneous multicentric lesions.

PATIENT CONCERNS

The both cases presented with severe headache with no significant past medical history.

DIAGNOSIS

PXA World Health Organization grade II were histopathologically diagnosed from surgically resected specimens, and immunohistochemical and sequence analysis revealed a high Ki-67 proliferative index and BRAF V600E mutation in both the cases.

INTERVENTIONS

The first case presented with multicentric lesions and underwent partial resection, whereas the second case presented with a tectal plate tumor that was managed by gross total surgical resection. Strong 5-aminolevulinic acid (5-ALA)-induced fluorescence was observed in both the lesions. Postoperative radiotherapy plus concomitant and adjuvant temozolomide was administered to both the patients.

OUTCOMES

Despite completing adjuvant chemo-radiotherapy, both the patients had local tumor recurrence at 2 and 5 months after the operation, respectively.

CONCLUSION

The progressive clinical courses in our cases suggest that additional postoperative therapy should be considered during the treatment of PXA with a high Ki67 index, and that temozolomide with radiotherapy, followed by temozolomide maintenance therapy, may not prevent recurrence in such tumors. Importantly, our experience implies that unlike other subtypes of low grade gliomas, 5-ALA fluorescence is useful for intraoperative visualization of PXA.

Evaluation of EZH2 expression, BRAF V600E mutation, and CDKN2A/B deletions in epithelioid glioblastoma and anaplastic pleomorphic xanthoastrocytoma

INTRODUCTION

Epithelioid glioblastoma (EGBM) and anaplastic pleomorphic xanthoastrocytoma (APXA) are two rare entities with different prognoses. However, they share certain morphological and molecular features. MATERIALS AND METHODS: To better recognize EGBM and APXA and identify the prognostic factors associated with these tumors, EZH2 status, BRAF V600E mutations, and CDKN2A/B deletions were assessed in 15 APXA and 13 EGBM cases.

RESULTS

The expression level of EZH2 was found to increase with tumor grade. Overexpression of EZH2 occurred in 69.2% (9/13) of EGBM cases and 20% (3/15) of APXA cases. In addition, 72.7% (8/11) of EGBM and 12.5% (1/8) of APXA cases harbored a CDKN2A homozygous deletion based on fluorescence in situ hybridization. BRAF V600E mutations were detected in 80% (8/10) of EGBM cases and 42.9% (3/7) of APXA cases. Furthermore, EGBM, which exhibited co-existing low-grade glioma-like lesions, was found to have strong EZH2 expression and high Ki-67 indexes only in epithelioid cells and not in low grade lesions. Univariate analysis demonstrated that abundant epithelioid cells, extensive necrosis, EZH2 overexpression and BRAF V600E mutations were significantly associated with decreased overall survival in EGBM and APXA patients (P < 0.05).

CONCLUSIONS

The results suggested that testing for EZH2 expression and BRAF V600E mutations might be helpful to evaluate the prognoses of EGBM and APXA patients. The presence of heterogeneous EZH2 expression in biphasic EGBMs could also contribute to malignant progression.

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.

Papillary glioblastoma exhibiting a neuroradiological cyst with a mural nodule: A case report

RATIONALE

Glioblastomas are malignant, infiltrating gliomas classified as grade IV by the World Health Organization. Genetically, most glioblastomas do not exhibit the isocitrate dehydrogenase (IDH) 1/2 gene mutation and rarely harbor the 1p/19q co-deletion. Neuroradiologically, glioblastomas rarely form a cyst with a mural nodule lesion.

PATIENT CONCERNS

In this study, a 78-year-old woman, with speech difficulty and forgetfulness, had a cystic tumor with a mural nodule in the right frontoparietal lobe. Therefore, partial tumor resection was performed.

DIAGNOSIS

Histopathology of the tumor, a glioblastoma, exhibited pseudopapillary features with non-hyalinized capillary cores and rich mini-gemistocytic cells. Genetic analysis of the tumor revealed co-deletion of 1p36/19q13, with wild-type IDH.

INTERVENTIONS

The patient underwent a combination of postoperative radiotherapy and temozolomide chemotherapy before leaving the hospital. After discharge, she was treated by 20 courses of temozolomide chemotherapy.

OUTCOMES

The patient is free from tumor recurrence 23 months after the operation.

LESSONS

We present a unique case of glioblastoma that exhibited novel neuroradiological, histopathological, and genetic features with a favorable prognosis for the patient. Therefore, a compilation of similar cases with clinicopathological and genetic analyses to characterize this unique glioblastoma is critical. Clinical evidence will help develop effective therapeutic approaches to improve prognosis in patients with glioblastoma.

BRAF V600E-mutated central nervous system tumor with divergent morphological feature - Anaplastic pleomorphic xanthoastrocytoma-like and astroblastoma-like

Mutational analysis of the BRAF gene (BRAF), especially BRAF V600E, is gaining much importance in neuro-oncology practice due to its diagnostic, prognostic and therapeutic implications. This genetic alteration has been described in a wide morphological spectrum of central nervous system tumors. In the present report we describe a BRAF V600E-mutated tumor with divergent morphological appearance comprising of anaplastic pleomorphic xanthoastrocytoma and astroblastoma. Both of these tumor entities are extremely rare and a combined morphology has not been described till now.

Pleomorphic xanthoastrocytomas of adults: MRI features, molecular markers, and clinical outcomes

Fifty adult patients with pathologically-confirmed pleomorphic xanthoastrocytomas (PXAs) were retrospectively analyzed. Adult PXAs appeared as a single lesion in 47 patients and multiple lesions in 3 patients. Temporal lobe was the most common location (17/50). Twenty-two cases were superficial with obvious meningeal contact and 9 were closely adjacent to lateral ventricles. Three imaging patterns were differentiated, including a predominantly solid mass with or without cystic changes (n = 33), a predominantly cystic mass with an obvious mural nodule (n = 14), and a predominantly cystic mass with an uneven wall thickness (n = 3). The mean tumoral apparent diffusion coefficient (ADC) was 0.83 ± 0.17 × 10⁻³ mm²/s, and the mean ADC ratio was 1.02 ± 0.22. The V-raf murine sarcoma viral oncogenes homolog B1 (BRAF)^V600E mutation was found in 12 of 29 patients. In 36 patients with isocitrate dehydrogenases 1 and 2 (IDH1/2) data, only one had IDH1 mutation and no patient had IDH2 mutation. Anaplastic features were common (24/50) and significantly associated with high rates of recurrence or progression (P < 0.001). In conclusion, this study expands our knowledge on the MRI features, molecular markers, and clinical outcomes of adult PXAs, to some extent different from pediatric PXAs.

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

BACKGROUND

Anaplastic pleomorphic xanthoastrocytoma (PXA) was added to grade III glial tumors as a distinct entity in the 2016 World Health Organization (WHO) classification of tumors of the central nervous system. We retrospectively reviewed and analyzed 55 pathologically confirmed PXA cases according to the newest WHO classification to better clarify the clinical, molecular, and prognostic features of this rare neoplasm.

METHODS

In total, 55 pathologically confirmed PXA cases according to the newest WHO classification were retrospectively reviewed and analyzed. After sequencing for BRAF, TERT, IDH1/2, and H3F3A, survival analysis was performed to determine the factors affecting survival.

RESULTS

The patients with BRAF V600E mutations were generally younger than those without it, although not statistically significant (27.9 ± 15.4 years and 37.1 ± 17.0 years, respectively, P = 0.054). TERT promoter mutation frequency in PXA was lower than in patients with anaplastic PXA although not statistically significant (4.4% and 28.6%, P = 0.083). One instance of PXA with IDH2 mutation, and no IDH1 and H3F3A mutations were found. In terms of prognosis, patients with anaplastic PXA had shorter overall survival and progression-free survival compared with patients with PXA. The subgroup with gross total resection had a longer median OS (not reached vs. 60.0 months, P = 0.0221) and PFS (not reached vs. 60.0 months, P = 0.0232) compared with patients with PXA with subtotal resection.

CONCLUSIONS

The identification of BRAF V600E, TERT, and IDH2 mutations in PXA expands our molecular understanding of PXA. Patients with PXA with gross total resection achieve good outcomes.

Molecular pathogenesis and therapeutic implications in pediatric high-grade gliomas

High-grade gliomas (HGG) are the most common malignant brain tumors in the pediatric population and account for a large subset of all pediatric central nervous system neoplasms. The management of pediatric HGG continues to be challenging, with poor outcome in many cases despite aggressive treatments. Consequently, parallel research efforts have been focused on identifying the underlying genetic and biological basis of pediatric HGG in order to more clearly define prognostic subgroups for treatment stratification as well as identify new treatment targets. These cutting-edge advances have revolutionized pediatric neuro-oncology and have revealed novel oncogenic vulnerabilities that are being therapeutically leveraged. Promising treatments - including pathway-targeting small molecules as well as epigenetic therapy - are being evaluated in clinical trials, and recent genomic discoveries in rare glioma subgroups have led to the identification of additional new potentially-actionable alterations. This review summarizes the current state of knowledge about the molecular characterization of pediatric HGG in correlation to the revised World Health Organization (WHO) classification, as well as provides an overview of some targeted treatment approaches in the modern clinical management of high-grade gliomas.

Recurrent copy number alterations in low-grade and anaplastic pleomorphic xanthoastrocytoma with and without BRAF V600E mutation

Pleomorphic xanthoastrocytoma (PXA) is a rare localized glioma characterized by frequent BRAF V600E mutation and CDKN2A/B deletion. We explored the association of copy-number variants (CNVs) with BRAF mutations, tumor grade, and patient survival in a cohort of 41 PXA patients using OncoScan chromosomal microarray. Primary resection specimens were available in 38 cases, including 24 PXA and 14 anaplastic PXA (A-PXA), 23 BRAF V600E mutant tumors (61%). CNVs were identified in all cases and most frequently involved chromosome 9 with homozygous CDKN2A/B deletion (n = 33, 87%), a higher proportion than previously detected by comparative genomic hybridization (50%-60%) (37). CDKN2A/B deletion was present in similar proportion of PXA (83%), A-PXA (93%), BRAF V600E (87%), and wild-type (87%) tumors. Whole chromosome gains/losses were frequent, including gains +7 (n = 15), +2 (n = 11), +5 (n = 10), +21 (n = 10), +20 (n = 9), +12 (n = 8), +15 (n = 8), and losses -22 (n = 11), -14 (n = 7), -13 (n = 5). Losses and copy-neutral loss of heterozygosity were significantly more common in A-PXA, involving chromosomes 22 (P = 0.009) and 14 (P = 0.03). Amplification of 8p and 12q was identified in a single tumor. Histologic grade was a robust predictor of overall survival (P = 0.003), while other copy-number changes, including CDKN2A/B deletion, did not show significant association with survival. Distinct histologic patterns of anaplasia included increased mitotic activity in an otherwise classic PXA or associated with small cell, fibrillary, or epithelioid morphology, with loss of SMARCB1 expression in one case. In 10 cases, matched specimens were compared, including A-PXA with areas of distinct low- and high-grade morphology (n = 2), matched primary/tumor recurrence (n = 7), or both (n = 1). Copy-number changes on recurrence/anaplastic transformation were complex and highly variable, from nearly identical profiles to numerous copy-number changes. Overall, we confirm CDKN2A/B deletion as key a feature of PXA not associated with tumor grade or BRAF mutation, but central to the underlying genetics of PXA.

The new WHO 2016 classification of brain tumors-what neurosurgeons need to know

BACKGROUND

The understanding of molecular alterations of tumors has severely changed the concept of classification in all fields of pathology. The availability of high-throughput technologies such as next-generation sequencing allows for a much more precise definition of tumor entities. Also in the field of brain tumors a dramatic increase of knowledge has occurred over the last years partially calling into question the purely morphologically based concepts that were used as exclusive defining criteria in the WHO 2007 classification.

METHODS

Review of the WHO 2016 classification of brain tumors as well as a search and review of publications in the literature relevant for brain tumor classification from 2007 up to now.

RESULTS

The idea of incorporating the molecular features in classifying tumors of the central nervous system led the authors of the new WHO 2016 classification to encounter inevitable conceptual problems, particularly with respect to linking morphology to molecular alterations. As a solution they introduced the concept of a "layered diagnosis" to the classification of brain tumors that still allows at a lower level a purely morphologically based diagnosis while partially forcing the incorporation of molecular characteristics for an "integrated diagnosis" at the highest diagnostic level. In this context the broad availability of molecular assays was debated. On the one hand molecular antibodies specifically targeting mutated proteins should be available in nearly all neuropathological laboratories. On the other hand, different high-throughput assays are accessible only in few first-world neuropathological institutions. As examples oligodendrogliomas are now primarily defined by molecular characteristics since the required assays are generally established, whereas molecular grouping of ependymomas, found to clearly outperform morphologically based tumor interpretation, was rejected from inclusion in the WHO 2016 classification because the required assays are currently only established in a small number of institutions.

CONCLUSION

In summary, while neuropathologists have now encountered various challenges in the transitional phase from the previous WHO 2007 version to the new WHO 2016 classification of brain tumors, clinical neurooncologists now face many new diagnoses allowing a clearly improved understanding that could offer them more effective therapeutic opportunities in neurooncological treatment. The new WHO 2016 classification presumably presents the highest number of modifications since the initial WHO classification of 1979 and thereby forces all professionals in the field of neurooncology to intensively understand the new concepts. This review article aims to present the basic concepts of the new WHO 2016 brain tumor classification for neurosurgeons with a focus on neurooncology.

Rare glial tumors

This chapter describes the epidemiology, pathology, molecular characteristics, clinical and neuroimaging features, treatment, outcome, and prognostic factors of the rare glial tumors. This category includes subependymal giant cell astrocytoma, pleomorphic xanthoastrocytoma, astroblastoma, chordoid glioma of the third ventricle, angiocentric glioma, ganglioglioma, desmoplastic infantile astrocytoma and ganglioma, dysembryoplastic neuroepithelial tumor, papillary glioneuronal tumor, and rosette-forming glioneuronal tumor of the fourth ventricle. Many of these tumors, in particular glioneuronal tumors, prevail in children and young adults, are characterized by pharmacoresistant seizures, and have an indolent course, and long survival following surgical resection. Radiotherapy and chemotherapy are reserved for recurrent and/or aggressive forms. New molecular alterations are increasingly recognized.

BRAF inhibitors in BRAF-V600 mutated primary neuroepithelial brain tumors

INTRODUCTION

Primary neuroepithelial brain tumors encompass a wide variety of glial and glioneuronal neoplasms. Malignant tumors, tumors located in surgically inaccessible locations (e.g., eloquent brain areas, deep structures, brain stem) and recurrent or progressive tumors pose considerable treatment challenges and are candidates for novel therapeutics based on molecular insights. Small kinase inhibitors of v-RAF murine sarcoma viral oncogene homologue B1 (BRAF) have shown considerable antineoplastic activity in some tumor types harboring activating BRAF-V600 mutations (e.g., melanoma) and promising data are emerging on BRAF inhibitor therapy of mutation-bearing primary brain tumors.

AREAS COVERED

This review summarizes the available data on BRAF-V600 point mutations and the antineoplastic activity and toxicity profiles of BRAF inhibitors in neuroepithelial brain tumors including diffuse gliomas (glioblastomas, astrocytomas, oligodendrogliomas), pilocytic astrocytomas, pleomorphic xanthoastrocytomas and gangliogliomas.

EXPERT OPINION

Activating BRAF-V600 mutations are recurrently found in several glial and glioneuronal brain tumors and the available data indicate that BRAF inhibitors are active and well-tolerated in such tumors. Thus, BRAF inhibitors represent a novel and promising therapeutic opportunity that may alter the disease course of molecularly selected CNS neoplasms in a clinically meaningful way. However, so far the evidence is anecdotal and prospective clinical studies should be conducted.

Analysis of IDH1-R132 mutation, BRAF V600 mutation and KIAA1549-BRAF fusion transcript status in central nervous system tumors supports pediatric tumor classification

OBJECTIVE

Gliomas are the leading cause of cancer-related morbidity in children and comprise a clinical, histological and molecular heterogenous group of CNS tumors. Appropriate treatment of these tumors relies on correct classification into tumor types and malignancy grades.

METHODS

We examined 170 (0-18 years) pediatric and 131 (19-35 years) young adult brain tumors including pilocytic astrocytomas (PAs), pilomyxoid astrocytomas (PMAs), diffuse astrocytomas (DAs), gangliogliomas, dysembryoplastic neuroepithelial tumors (DNTs) and pleomorphic xanthoastrocytomas (PXAs) for IDH1 and BRAF mutation/BRAF fusion gene status. The obtained data were compared to results in 464 (<35 years) adult brain tumors. In 32 tumors with an oligodendroglial or mixed glioma differentiation, additionally the LOH1p/19q status was determined.

RESULTS

By combining immunohistochemistry and molecular methods, IDH1/2 mutations were observed in 6 pediatric, 35 young adult and 43 adult tumors of the astrocytic/oligodendroglial lineage. BRAF V600E mutations (20 pediatric, 7 young adults and 2 adults) were found mostly in gangliogliomas, PXAs, few astrocytomas and few DNTs. Except for one DA case, BRAF fusions (35 pediatric, 8 young adults and 2 adults) were restricted to PA and PMA and associated with age and infratentorial location. All mutations were mutually exclusive and always present in the primary tumor. Two-thirds of all pediatric samples harbored one of the three examined mutations.

CONCLUSION

Combination of IDH1-R132, BRAF V600 and KIAA1549-BRAF fusion analysis is therefore a useful tool to increase diagnostic accuracy in pediatric gliomas.

BRAF alterations in brain tumours: molecular pathology and therapeutic opportunities

PURPOSE OF REVIEW

To summarize the current knowledge on v-RAF murine sarcoma viral oncogene homologue B1 (BRAF) aberrations in tumours of the central nervous system.

RECENT FINDINGS

BRAF alterations are found in variable frequencies across a wide spectrum of diverse central nervous system neoplasms. BRAF V600 point mutations (most commonly of the V600E type) are most common in pleomorphic xanthoastrocytoma (approximately 60% of cases), gangliogliomas (50%), dysembryoplastic neuroepithelial tumours (30%), Langerhans cell histiocytosis (50%), melanoma brain metastases (50%) and papillary craniopharyngiomas (96%) and are also detectable in a fraction of glioblastomas (overall mutation rate of 2-12%, with a higher rate of approximately 50% in epithelioid glioblastomas). BRAF fusions (most commonly KIAA1549: BRAF) are typical for pilocytic astrocytomas and are almost absent from other tumour types. Clinical trials have established tyrosine-kinase inhibitors of BRAF as feasible treatment option in selected patients with mutation-bearing brain metastases of melanoma. Preclinical studies, some case reports and small patient series have documented tumour responses of primary brain tumours with BRAF aberrations to BRAF inhibition.

SUMMARY

Molecular testing for BRAF alterations in brain tumours may be of clinical relevance for differential diagnostic considerations in some situations or to guide selection of patients for targeted therapy with specific inhibitors. Prospective clinical trials evaluating the efficacy of BRAF inhibitors in central nervous system tumours are strongly supported by the available evidence.

BRAF VE1 immunoreactivity patterns in epithelioid glioblastomas positive for BRAF V600E mutation

Epithelioid glioblastomas (E-GBMs) manifest BRAF V600E mutation in up to 50% of cases, compared with a small percentage of ordinary GBMs, suggesting that they are best considered variants rather than a different pattern of GBM. Availability of a targeted therapy, vemurafenib, may make testing BRAF status important for treatment. It is unclear whether BRAF VE1 immunohistochemistry (IHC) can substitute for Sanger sequencing in these tumors. BRAF VE1 IHC was correlated with Sanger sequencing results on our original cohort of E-GBMs, and then new E-GBM cases were tested with both techniques (n=20). Results were compared with those in similarly assessed giant cell GBMs, anaplastic pleomorphic xanthoastrocytomas. All tumors tested showed 1:1 correlation between BRAF V600E mutational results and IHC. However, heavy background immunostaining in some negatively mutated cases resulted in equivocal results that required repeat IHC testing and additional mutation testing using a different methodology to confirm lack of detectable BRAF mutation. Mutated/BRAF VE1 IHC E-GBMs and anaplastic pleomorphic xanthoastrocytomas tended to manifest strong, diffuse cytoplasmic immunoreactivity, compared with previously studied gangliogliomas, which demonstrate more intense immunoreactivity in the ganglion than in the glial tumor component. One of our E-GBM patients with initial gross total resection quickly recurred within 4 months, required a second resection, and then was placed on vemurafenib; she remains tumor free 21 months after second resection without neuroimaging evidence of residual disease, adding to the growing number of reports of successful treatment of BRAF-mutated glial tumors with drug. E-GBMs show good correlation between mutational status and IHC, albeit with limitations to IHC. E-GBMs can respond to targeted therapy.

Pleomorphic Xanthoastrocytoma: Natural History and Long-Term Follow-Up

Prognostic significance of histological anaplasia and BRAF V600E mutation were retrospectively evaluated in 74 patients with pleomorphic xanthoastrocytoma (PXA). Median age at diagnosis was 21.5 years (31 pediatric, 43 adult) and median follow-up 7.6 years. Anaplasia (PXA-AF), defined as mitotic index ≥ 5/10 HPF and/or presence of necrosis, was present in 33 cases. BRAF V600E mutation was detected in 39 (of 60) cases by immunohistochemical and/or molecular analysis, all negative for IDH1 (R132H). Mitotic index ≥ 5/10 HPF and necrosis were associated with decreased overall survival (OS; P = 0.0005 and P = 0.0002, respectively). In all cases except two, necrosis was associated with mitotic index ≥ 5/10 HPF. Patients with BRAF V600E mutant tumors had significantly longer OS compared with those without BRAF V600E mutation (P = 0.02). PXA-AF patients, regardless of age, had significantly shorter OS compared with those without (P = 0.0003). Recurrence-free survival was significantly shorter for adult PXA-AF patients (P = 0.047) only. Patients who either recurred or died ≤ 3 years from diagnosis were more likely to have had either PXA-AF at first diagnosis (P = 0.008) or undergone a non-gross total resection procedure (P = 0.004) as compared with patients who did not. This study provides further evidence that PXA-AF behaves more aggressively than PXA and may qualify for WHO grade III "anaplastic" designation.

Massive dissemination from spinal cord gangliogliomas negative for BRAF V600E: report of two rare adult cases

OBJECTIVES

Metastatic leptomeningeal spread from spinal cord gangliogliomas (GGs) is exceedingly rare.

METHODS

Two adult women, aged 27 and 51 years, died of massive disseminations of cervicothoracic GGs 4 and 6 years, respectively, after initial diagnoses; full autopsies were performed. BRAF status was assessed by VE1 immunohistochemistry (IHC), Sanger sequencing, and a single-nucleotide base extension assay (SNaPshot, Applied Biosystems, Princeton, NJ).

RESULTS

The 27-year-old underwent two biopsies, chemotherapy, radiation, and ventriculoperitoneal shunt placement; she developed craniospinal and peritoneal dissemination. Autopsy confirmed shunt-mediated peritoneal metastases, microscopic bone marrow involvement, and profuse spinal and supratentorial leptomeningeal and parenchymal spread. The 51-year-old underwent two resections, radiation, and chemotherapy and developed pancytopenia with biopsy-proven bony metastases 15 months before death. Autopsy demonstrated leptomeningeal, subpial, and subependymal metastases. The tumors in both primary and metastatic sites were BRAF negative by VE1 IHC and two different mutational analyses. This compared with negative BRAF results for an additional four nonmetastatic adult nonsupratentorial GGs and in our study.

CONCLUSIONS

We document two rare cases of massively metastatic spinal cord GGs in adult patients who were negative for BRAF V600E mutations via multiple methods.

Predictive biomarkers in adult gliomas: the present and the future

PURPOSE OF REVIEW

This review summarizes recent studies on the predictive value of molecular markers in adult gliomas, including 1p/19q codeletion, MGMT methylation, IDH mutation and markers identified using omics and next-generation sequencing studies.

RECENT FINDINGS

The long-term results of the Radiation Therapy Oncology Group and European Organization for Research and Treatment of Cancer trials in anaplastic oligodendroglial glioma have shown that the 1p/19q codeletion predicts an overall survival benefit from early PCV (procarbazine CCNU vincristine) chemotherapy. This benefit can also be predicted using gene expression-based molecular subtypes of gliomas while the predictive value of the IDH mutation in this context requires further study. In elderly patients with glioblastoma, the analysis of MGMT methylation status in two phase III trials suggests that this alteration may guide treatment decisions; however, this finding still needs confirmation in prospective studies. Omics and next-generation sequencing studies have identified additional potential predictive markers. In particular, IDH mutations, BRAF V600E mutations and FGFR gene fusions might predict efficacy of therapies targeted against these alterations.

SUMMARY

Currently, the 1p/19q codeletion is the only well established predictive marker with clinical utility. However, it is likely that other molecular markers such as MGMT methylation, IDH mutation and those identified using omics and next-generation sequencing studies will further guide treatment decisions in adult gliomas.

BRAF-mutated pleomorphic xanthoastrocytoma is associated with temporal location, reticulin fiber deposition and CD34 expression

BRAF V600E mutation and homozygous deletion of CDKN2A (p16) are frequent molecular alterations in pleomorphic xanthoastrocytomas (PXAs). We investigated 49 PXAs for clinical, histological and immunohistochemical characteristics related to BRAF mutation status. BRAF mutation was detected by immunohistochemical assay and DNA sequencing in 38/49 (78%) tumors. All but one PXA located in the temporal lobe harbored a BRAF V600E mutation (23/24; 96%) compared with 10/19 nontemporal PXAs (53%; P = 0.0009). Histological and immunohistochemical analysis demonstrated increased reticulin deposition (76% vs. 27%; P = 0.003) and a more frequent expression of CD34 in BRAF-mutant PXAs (76% vs. 27%; P = 0.003). We further investigated the utility of combined BRAF V600E (VE1) and p16 analysis by immunohistochemistry to distinguish PXAs from relevant histological mimics like giant-cell glioblastoma. Among PXAs, 38/49 (78%) were VE1-positive, and 30/49 (61%) had a loss of p16 expression. The combined features (VE1 positivity/p16 loss) were observed in 25/49 PXAs (51%) but were not observed in giant-cell glioblastoma (VE1 0/28, p16 loss 14/28). We demonstrate that temporal location, reticulin deposition and CD34 expression are associated with BRAF mutation in PXA. Combined VE1 positivity and p16 loss represents a frequent immunoprofile of PXA and may therefore constitute an additional diagnostic tool for its differential diagnosis.

The diagnostic role and clinical relevance of determination of BRAF status in brain tumors

BRAF protein is a serine/threonine kinase that serves as an immediate downstream effector of the MAPK signaling cascade, a signal transduction pathway that modulates cell proliferation and survival. BRAF alterations leading to MAPK pathway activation have been identified in gliomas and glioneuronal tumors of the CNS. Whereas BRAF mutations have been found in a wide spectrum of CNS tumors, BRAF fusions have been almost exclusively found in pilocytic astrocytomas. BRAF fusion identification provides an additional help in the differential diagnosis of supratentorial gliomas. Although the prognostic significance of BRAF alterations in different CNS tumors is still under investigation, the evidence of BRAF-dependent MAPK-pathway activation in gliomas has moreover drawn attention to the potential use of MEK1/2 and RAF inhibitors in clinical neuro-oncology. Given the promising results of the therapeutic management of several cancer types, clinical studies investigating the suitability of such inhibitors for the therapy of gliomas are ongoing.