BRAF-V600E immunohistochemistry in a large series of glial and glial-neuronal tumors

The Clinical Utility of a Tiered Approach to Pediatric Glioma Molecular Characterization for Resource-Limited Settings

PURPOSE

Molecular characterization is key to optimally diagnose and manage cancer. The complexity and cost of routine genomic analysis have unfortunately limited its use and denied many patients access to precision medicine. A possible solution is to rationalize use-creating a tiered approach to testing which uses inexpensive techniques for most patients and limits expensive testing to patients with the highest needs. Here, we tested the utility of this approach to molecularly characterize pediatric glioma in a cost- and time-sensitive manner.

METHODS

We used a tiered testing pipeline of immunohistochemistry (IHC), customized fusion panels or fluorescence in situ hybridization (FISH), and targeted RNA sequencing in pediatric gliomas. Two distinct diagnostic algorithms were used for low- and high-grade gliomas (LGGs and HGGs). The percentage of driver alterations identified, associated testing costs, and turnaround time (TAT) are reported.

RESULTS

The tiered approach successfully characterized 96% (95 of 99) of gliomas. For 82 LGGs, IHC, targeted fusion panel or FISH, and targeted RNA sequencing solved 35% (29 of 82), 29% (24 of 82), and 30% (25 of 82) of cases, respectively. A total of 64% (53 of 82) of samples were characterized without targeted RNA sequencing. Of 17 HGG samples, 13 were characterized by IHC and four were characterized by targeted RNA sequencing. The average cost per sample was more affordable when using the tiered approach as compared with up-front targeted RNA sequencing in LGG ($405 US dollars [USD] v $745 USD) and HGGs ($282 USD v $745 USD). The average TAT per sample was also shorter using the tiered approach (10 days for LGG, 5 days for HGG v 14 days for targeted RNA sequencing).

CONCLUSION

Our tiered approach molecularly characterized 96% of samples in a cost- and time-sensitive manner. Such an approach may be feasible in neuro-oncology centers worldwide, particularly in resource-limited settings.

Pathophysiological evaluation of pilocytic astrocytoma in adults: Histopathological and immunohistochemical analysis

Pilocytic astrocytoma is a central nervous system tumor of slow growth, which represents 5 % of all gliomas and most often develops in the cerebellum (42-60 %), but can also arise in other neural areas, such as the optic pathway or hypothalamus (9-30 %); brainstem (9 %); spinal cord (2 %). In the pediatric population, this tumor is the second most common cause of neoplasms and, on the other hand, in adults, it is often rare, probably due to its aggressiveness in these individuals. Studies reveal that the origin of pilocytic astrocytoma is characterized by a fusion between the BRAF gene and the KIAA1549 locus, and the application of the immunohistochemistry technique for the analysis of BRAF protein expression can be a valuable tool for diagnostic purposes. Due to the relative rarity of this disease in adults, there are few publications on the most effective diagnostic and treatment strategies for this tumor. The general objective of this study was to analyze the histopathological and immunohistochemical characteristics of pilocytic astrocytoma in these patients. For this, a retrospective study of patients aged over 17 years with a diagnosis of pilocytic astrocytoma was carried out at the Department of Pathology of UNIFESP/EPM, from 1991 to 2015. In order to define BRAF positivity in the immunohistochemical analysis, at least three consecutive fields with more than 50 % immunostaining were used as criteria and, thus, it was inferred that the 7 cases analyzed were considered positive for the cytoplasmic marker BRAF V600E. Histopathological analysis associated with BRAF immunostaining is of paramount importance as a diagnostic method in these cases. However, future molecular studies will be necessary both for a better understanding of the aggressiveness and prognostic of this tumor and for research involving specific therapies for pilocytic astrocytoma in adults.

Pediatric brain tumors: A neuropathologist's approach to the integrated diagnosis

The classification of tumors of the central nervous system (CNS) is a rapidly evolving field. While tumors were historically classified on the basis of morphology, the recent integration of molecular information has greatly refined this process. In some instances, molecular alterations provide significant prognostic implications beyond what can be ascertained by morphologic examination alone. Additionally, tumors may harbor molecular alterations that provide a therapeutic target. Pediatric CNS tumors, in particular, rely heavily on the integration of molecular data with histologic, clinical, and radiographic features to reach the most accurate diagnosis. This review aims to provide insight into a neuropathologist's approach to the clinical workup of pediatric brain tumors with an ultimate goal of reaching an integrated diagnosis that provides the most accurate classification and informs prognosis and therapy selection. The primary focus will center on how histology and molecular findings are used in combination with clinical and radiographic information to reach a final, integrated diagnosis.

NTRK2 gene fusions are uncommon in pilocytic astrocytoma

BACKGROUND

Pilocytic astrocytoma is the most frequent pediatric glioma. Despite its overall good prognosis, complete surgical resection is sometimes unfeasible, especially for patients with deep-seated tumors. For these patients, the identification of targetable genetic alterations such as NTRK fusions, raised as a new hope for therapy. The presence of gene fusions involving NTRK2 has been rarely reported in pilocytic astrocytoma. The aim of the present study was to investigate the frequency of NTRK2 alterations in a series of Brazilian pilocytic astrocytomas.

METHODS

Sixty-nine pilocytic astrocytomas, previously characterized for BRAF and FGFR1 alterations were evaluated. The analysis of NTRK2 alterations was performed using a dual color break apart fluorescence in situ hybridization (FISH) assay.

RESULTS

NTRK2 fusions were successfully evaluated by FISH in 62 of the 69 cases. Neither evidence of NTRK2 gene rearrangements nor NTRK2 copy number alterations were found.

CONCLUSIONS

NTRK2 alterations are uncommon genetic events in pilocytic astrocytomas, regardless of patients' clinicopathological and molecular features.

Molecular alterations of low-grade gliomas in young patients: Strategies and platforms for routine evaluation

In recent years, it has been established that molecular biology of pediatric low-grade gliomas (PLGGs) is entirely distinct from adults. The majority of the circumscribed pediatric gliomas are driven by mitogen-activated protein kinase (MAPK) pathway, which has yielded important diagnostic, prognostic, and therapeutic biomarkers. Further, the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy (cIMPACT) Steering Committee in their fourth meeting, suggested including a panel of molecular markers for integrated diagnosis in "pediatric-type" diffuse gliomas. However, a designated set of platforms for the evaluation of these alterations has yet not been mentioned for easier implementation in routine molecular diagnostics. Herein, we have reviewed the relevance of analyzing these markers and discussed the strategies and platforms best apposite for clinical laboratories.

Assessing the utility and attitudes toward molecular testing in neuro-oncology: a survey of the Society for Neuro-Oncology members

BACKGROUND

Molecular testing (MT) is utilized in neuro-oncology with increasing frequency. The aim of this study was to determine clinical practice patterns to acquire this information, interpret and utilize MT for patient care, and identify unmet needs in the practical clinical application of MT.

METHODS

We conducted a voluntary online survey of providers within the Society for Neuro-Oncology (SNO) membership database between March and April 2019.

RESULTS

We received 152 responses out of 2022 SNO members (7.5% of membership). 88.8% of respondents routinely order MT for newly diagnosed gliomas. Of those who do not, testing is preferentially performed in younger patients or those with midline tumors. 82.8% use MT in recurrent gliomas. Other common indications included: metastatic tumors, meningioma, and medulloblastoma. Many providers utilize more than one resource (36.0%), most frequently using in-house (41.8%) over commercially available panels. 78.1% used the results for clinical decision-making, with BRAF, EGFR, ALK, and H3K27 mutations most commonly directing treatment decisions. Approximately, half (48.5%) of respondents have molecular tumor boards at their institutions. Respondents would like to see SNO-endorsed guidelines on MT, organized lists of targeted agents available for specific mutations, a database of targetable mutations and clinical trials, and more educational programs on MT.

CONCLUSION

This survey was marked by several limitations including response rate and interpretation of MT. Among respondents, there is routine use of MT in Neuro-Oncology, however, there remains a need for increased guidance for providers to effectively incorporate the expanding genomic data resulting from MT into daily Neuro-Oncology practice.

Detection of BRAF V600E Mutation in Ganglioglioma and Pilocytic Astrocytoma by Immunohistochemistry and Real-Time PCR-Based Idylla Test

The BRAF V600E mutation is an important oncological target in certain central nervous system (CNS) tumors, for which a possible application of BRAF-targeted therapy grows continuously. In the present study, we aim to determine the prevalence of BRAF V600E mutations in a series of ganglioglioma (GG) and pilocytic astrocytoma (PA) cases. Simultaneously, we decided to verify whether the combination of fully automated tests—BRAF-VE1 immunohistochemistry (IHC) and Idylla BRAF mutation assay—may be useful to accurately predict it in the case of specified CNS tumors. The study included 49 formalin-fixed, paraffin-embedded tissues, of which 15 were GG and 34 PA. Immunohistochemistry with anti-BRAF V600E (VE1) antibody was performed on tissue sections using the VentanaBenchMark ULTRA platform. All positive or equivocal cases on IHC and selected negative ones were further assessed using the Idylla BRAF mutation assay coupled with the Idylla platform. The BRAF-VE1 IHC was positive in 6 (6/49; 12.3%) and negative in 39 samples (39/49; 79.6%). The interpretation of immunostaining results was complicated in 4 cases, of which 1 tested positive for the Idylla BRAF mutation assay. Therefore, the overall positivity rate was 14.3%. This included 2 cases of GG and 5 cases of PA. Our study found that BRAF V600E mutations are moderately frequent in PA and GG and that for these tumor entities, IHC VE1 is suitable for screening purposes, but all negative, equivocal, and weak positive cases should be further tested with molecular biology techniques, of which the Idylla system seems to be a promising tool.

Clinical Relevance of BRAF V600E Mutation Status in Brain Tumors with a Focus on a Novel Management Algorithm

The possible application of BRAF-targeted therapy in brain tumors is growing continuously. We have analyzed clinical strategies that address BRAF activation in primary brain tumors and verified current recommendations regarding screening for BRAF mutations. There is preliminary evidence for a range of positive responses in certain brain tumor types harboring the BRAF V600E mutation. National Comprehensive Cancer Network Guidelines for central nervous system cancers recommend screening for the BRAF V600E mutation in pilocytic astrocytoma, pleomorphic xanthoastrocytoma, and ganglioglioma. We suggest additional testing in glioblastomas WHO grade IV below the age of 30 years, especially those with epithelioid features, papillary craniopharyngiomas, and pediatric low-grade astrocytomas. BRAF-targeted therapy should be limited to the setting of a clinical trial. If the patient harboring a V600E mutation does not qualify for a trial, multimodality treatment is recommended. Dual inhibition of both RAF and MEK is expected to provide more potent and durable effects than anti-BRAF monotherapy. First-generation RAF inhibitors should be avoided. Gain-of-function mutations of EGFR and KIAA fusions may compromise BRAF-targeted therapy. BRAF alterations that result in MAPK pathway activation are common events in several types of brain tumors. BRAF V600E mutation emerges as a promising molecular target. The proposed algorithm was designed to help oncologists to provide the best therapeutic options for brain tumor patients.

Prolonged Response Induced by Single Agent Vemurafenib in a BRAF V600E Spinal Ganglioglioma: A Case Report and Review of the Literature

Spinal ganglioglioma is a rare low-grade, slow-growing tumor of the central nervous system affecting mostly children and young adults. After surgery, some patients show tumor recurrence and/or malignant transformation. Gangliogliomas harbor molecular deficiencies such as mutations in the B-rapidly accelerated fibrosarcoma (BRAF) gene, resulting in activation of a downstream signaling pathway and cancer development. Vemurafenib is a BRAF inhibitor used to treat patients with BRAF V600E-mutated cancer. Although a few studies have reported the clinical responses in gangliogliomas, the sequence and duration of treatment have not been established. We describe a case of an adult with a progressive BRAF V600E mutant spinal cord ganglioglioma 9 years after surgery who was treated with vemurafenib. This treatment resulted in a partial response within 2 months, which was sustained for more than a year. The patient then decided to stop treatment because of side effects. Despite this decision, the tumor showed no sign of progression 21 months after treatment discontinuation. This is the first reported case of a response to vemurafenib in an adult with progressive spinal cord BRAF V600E-mutated ganglioglioma which was sustained after treatment discontinuation.

Dysembryoplastic neuroepithelial tumor-like pilocytic astrocytoma: A case report

RATIONALE

Pilocytic astrocytoma (PA) typically shows biphasic pattern with a mixture of loose microcystic and compact regions, in which it is not uncommon to see heterogeneous morphology. However, there has not been reported in the literatures of the PA type that shows similarity to dysembryoplastic neuroepithelial tumor (DNT) in both histological morphology and immunophenotype.

PATIENT CONCERNS

The present study described a case of PA affecting the right temporal-occipital lobe in a 22-year-old male patient. Morphologically, it composed of totally distinctive microcystic pattern. The classical biphasic pattern of PA was not observed. Immunohistochemically, neuronal marker NeuN was expressed in tumor cells scattered in the background which simulated its expression morphology in DNT. However, KIAA1549-BRAF fusion gene was identified by fluorescence in situ hybridization (FISH), supporting for the diagnosis of PA.

DIAGNOSES

DNT-like PA (WHO grade I).

INTERVENTIONS

The tumor was totally removed via a right temporal-occipital craniotomy.

OUTCOMES

The patient is free of local recurrence and dissemination eleven months after surgical resection of the lesion.

LESSONS

We herein report a rare case of DNT-like PA. For diagnosis, KIAA1549-BRAF fusion gene should be detected under similar situation.

BRAF-V600E immunohistochemistry in a large series of glial and glial-neuronal tumors

INTRODUCTION

Some glial-neuronal tumors (GNT) (pleomorphic xantho-astrocytoma [PXA], ganglioglioma [GG]) display BRAF-V600E mutation, which represents a diagnostic clue to these entities. Targeted therapies against BRAF-V600 protein have shown promising results in GNT. The aim of this study was to assess the utility of BRAF-V600E immunohistochemistry (IHC, clone VE1) in daily practice in a series of 140 glial, and GNT compared to molecular biology (MB) techniques.

METHODS

We performed BRAF-V600E IHC on all 140 cases. We used Sanger sequencing and allele-specific quantitative PCR (ASQ-PCR) to detect BRAF-V600E mutation when sufficient amount of materiel was available.

RESULTS

BRAF-V600E immunostaining was detected in 29.5% of cases (41/140 cases; 61.5% GG/GC/AGG (32/52), 33% PXA, 6.6% pilocytic astrocytomas). In 47 cases, MB could be performed: Sanger sequencing and ASQ-PCR in 34 cases, ASQ-PCR only in 11 cases, and Sanger sequencing only in two cases. In initial tumors, Sanger sequencing identified BRAF-V600E mutation in 19.5% tumors (seven of 36 tested cases). ASQ-PCR showed mutation in 48.5% tumors (17/35 tested cases). In six cases (5 GG, one PXA), the results were discordant between IHC and MB; the five GG cases were immunopositive for BRAF-V600E but wild type with both MB techniques. In another 7 GG, the percentage of mutated (ganglion) cells was low, and Sanger sequencing failed to detect the mutation, which was detected by IHC and ASQ-PCR.

CONCLUSIONS

In tumors with few mutated cells (e.g., GG), anti-BRAF-V600E IHC appears more sensitive than Sanger sequencing. The latter, although considered as the gold standard, is not to be used up-front to detect BRAF mutation in GG. The combination of IHC and ASQ-PCR appears more efficient to appraise the indication of targeted therapies in these glioneuronal tumors.