Activating mutations in BRAF characterize a spectrum of pediatric low-grade gliomas

Natural history and neuro-oncological approach in spinal gangliogliomas: a systematic review

To describe the natural history of spinal gangliogliomas (GG) in order to determine the most appropriate neuro-oncological management. A Medline search for relevant publications up to July 2023 using the key phrase "ganglioglioma spinal" and "ganglioglioma posterior fossa" led to the retrieval of 178 studies. This corpus provided the basis for the present review. As an initial selection step, the following inclusion criteria were adopted: (i) series and case reports on spinal GG; (ii) clinical outcomes were reported specifically for GG; (iii) GG was the only pathological diagnosis for the evaluation of the tumor; (iv) papers written only in English was evaluated; and (v) papers describing each case in the series were included. The World Health Organization (WHO) 2021 grading criteria for gangliogliomas were applied. A total of 107 tumors were evaluated (63 from male patients and 44 from female patients; 1.43 male/1.0 female ratio, mean age 18.34 ± 15.84 years). The most common site was the cervical spine, accounting for 43 cases (40.18%); GTR was performed in 35 cases (32.71%) and STR in 71 cases (66.35%), while this information was not reported in 1 case (0.94%). 8 deaths were reported (7.47%) involving 2 males (25%) and 6 females (75%) aged 4-78 years (mean 34.27 ± 18.22) years. GGs located on the spine displayed the same gender ratio as these tumors in general. The most frequent symptom was pain and motor impairment, while the most prevalent location was the cervical spinal cord. GTR of the tumor posed a challenge for neurosurgeons, due to the difficulty of resecting the lesion without damaging the spinal eloquent area, explaining the lower rate of cure for this tumor type.

Clinicopathological analysis of BRAF and non-BRAF MAPK pathway-altered gliomas in paediatric and adult patients: a single-institution study of 40 patients

AIMS

Mitogen-activated protein kinase (MAPK) pathway alteration is a major oncogenic driver in paediatric low-grade gliomas (LGG) and some adult gliomas, encompassing BRAF (most common) and non-BRAF alterations. The aim was to determine the frequency, molecular spectrum and clinicopathological features of MAPK-altered gliomas in paediatric and adult patients at our neuropathology site in Kuwait.

METHODS

We retrospectively searched the data of molecularly sequenced gliomas between 2018 and 2023 for MAPK alterations, revised the pathology in view of the 2021 WHO classification and evaluated the clinicopathological data for possible correlations.

RESULTS

Of 272 gliomas, 40 (15%) harboured a MAPK pathway alteration in 19 paediatric (median 9.6 years; 1.2-17.6) and 21 adult patients (median 37 years; 18.9-89.2), comprising 42% and 9% of paediatric and adult cases, respectively. Pilocytic astrocytoma and glioblastoma were the most frequent diagnoses in children (47%) and adults (43%), respectively. BRAF V600E (n=17, 43%) showed a wide distribution across age groups, locations and pathological diagnoses while KIAA1549::BRAF fusion (n=8, 20%) was spatially and histologically restricted to cerebellar paediatric LGGs. Non-V600E variants and BRAF amplifications accompanied other molecular aberrations in high-grade tumours. Non-BRAF MAPK alterations (n=8) included mutations and gene fusions involving FGFR1, NTRK2, NF1, ROS1 and MYB. Fusions included KANK1::NTRK2, GOPC::ROS1 (both infant hemispheric gliomas), FGFR1::TACC1 (diffuse LGG), MYB::QKI (angiocentric glioma) and BCR::NTRK2 (glioblastoma). Paradoxical H3 K27M/MAPK co-mutations were observed in two LGGs.

CONCLUSION

The study provided insights into MAPK-altered gliomas in Kuwait highlighting the differences among paediatric and adult patients and providing a framework for planning therapeutic polices.

MRI characteristics predict BRAF V600E status in gangliogliomas and pleomorphic xanthoastrocytomas and provide survival prognostication

BACKGROUND

BRAF V600E mutation is a common genomic alteration in gangliogliomas (GGs) and pleomorphic xanthoastrocytomas (PXAs) with prognostic and therapeutic implications.

PURPOSE

To investigate the ability of magnetic resonance imaging (MRI) features to predict BRAF V600E status in GGs and PXAs and their prognostic values.

MATERIAL AND METHODS

A cohort of 44 patients with histologically confirmed GGs and PXAs was reviewed retrospectively. BRAF V600E status was determined by immunohistochemistry (IHC) staining and fluorescence quantitative polymerase chain reaction (PCR). Demographics and MRI characteristics of the two groups were evaluated and compared. Univariate and multivariate Cox regression analyses were performed to identify MRI features that were prognostic for progression-free survival (PFS).

RESULTS

T1/FLAIR ratio, enhancing margin, and mean relative apparent diffusion coefficient (rADCmea) value showed significant differences between the BRAF V600E-mutant and BRAF V600E-wild groups (all P < 0.05). Binary logistic regression analysis revealed only rADCmea value was the independent predictive factor for BRAF V600E status (P = 0.027). Univariate Cox regression analysis showed age at diagnosis (P = 0.032), WHO grade (P = 0.020), enhancing margin (P = 0.029), and rADCmea value (P = 0.005) were significant prognostic factors for PFS. In multivariate Cox regression analysis, increasing age (P = 0.040, hazard ratio [HR] = 1.04, 95% confidence interval [CI] = 1.002-1.079) and lower rADCmea values (P = 0.021, HR = 0.036, 95% CI = 0.002-0.602) were associated with poor PFS in GGs and PXAs.

CONCLUSION

Imaging features are potentially predictive of BRAF V600E status in GGs and PXAs. Furthermore, rADCmea value is a valuable prognostic factor for patients with GGs or PXAs.

A rare tumor in the sellar region: ganglioglioma, a case report and a general overview

BACKGROUND

Gangliogliomas are rare mixed neuronal-glial tumors of the central nervous system, accounting for less than 2% of intracranial tumors.

CASE DESCRIPTION

This report presents a rare case of ganglioglioma in the sellar region of a 3-year-old and 5-month-old pediatric patient. The patient underwent surgical intervention initially through a transnasal transsphenoidal approach and subsequently through a transcranial pterional craniotomy approach. Subsequently, radiotherapy and chemotherapy were administered for residual tumor tissue. The purpose of this report is to highlight the presence of ganglioglioma as a distinct diagnosis in sellar region tumors, discuss the surgical, radiotherapy, and/or chemotherapy treatment options for sellar region gangliogliomas based on the literature, and contribute the patient's follow-up and treatment outcomes to the existing literature.

CONCLUSION

Complete tumor resection may not be feasible in sellar region gangliogliomas, especially in pediatric cases, due to endocrinological and vision-related complications. In cases where complete resection is not possible, radiotherapy and/or chemotherapy may be considered. However, the optimal treatment approach has not yet been established, and further research is needed.

Radiomic features from multiparametric magnetic resonance imaging predict molecular subgroups of pediatric low-grade gliomas

BACKGROUND

We aimed to develop machine learning models for prediction of molecular subgroups (low-risk group and intermediate/high-risk group) and molecular marker (KIAA1549-BRAF fusion) of pediatric low-grade gliomas (PLGGs) based on radiomic features extracted from multiparametric MRI.

METHODS

61 patients with PLGGs were included in this retrospective study, which were divided into a training set and an internal validation set at a ratio of 2:1 based on the molecular subgroups or the molecular marker. The patients were classified into low-risk and intermediate/high-risk groups, BRAF fusion positive and negative groups, respectively. We extracted 5929 radiomic features from multiparametric MRI. Thereafter, we removed redundant features, trained random forest models on the training set for predicting the molecular subgroups or the molecular marker, and validated their performance on the internal validation set. The performance of the prediction model was verified by 3-fold cross-validation.

RESULTS

We constructed the classification model differentiating low-risk PLGGs from intermediate/high-risk PLGGs using 4 relevant features, with an AUC of 0.833 and an accuracy of 76.2% in the internal validation set. In the prediction model for predicting KIAA1549-BRAF fusion using 4 relevant features, an AUC of 0.818 and an accuracy of 81.0% were achieved in the internal validation set.

CONCLUSIONS

The current study demonstrates that MRI radiomics is able to predict molecular subgroups of PLGGs and KIAA1549-BRAF fusion with satisfying sensitivity.

TRIAL REGISTRATION

This study was retrospectively registered at clinicaltrials.gov (NCT04217018).

Unlocking the power of precision medicine for pediatric low-grade gliomas: molecular characterization for targeted therapies with enhanced safety and efficacy

In the past decade significant advancements have been made in the discovery of targetable lesions in pediatric low-grade gliomas (pLGGs). These tumors account for 30-50% of all pediatric brain tumors with generally a favorable prognosis. The latest 2021 WHO classification of pLGGs places a strong emphasis on molecular characterization for significant implications on prognosis, diagnosis, management, and the potential target treatment. With the technological advances and new applications in molecular diagnostics, the molecular characterization of pLGGs has revealed that tumors that appear similar under a microscope can have different genetic and molecular characteristics. Therefore, the new classification system divides pLGGs into several distinct subtypes based on these characteristics, enabling a more accurate strategy for diagnosis and personalized therapy based on the specific genetic and molecular abnormalities present in each tumor. This approach holds great promise for improving outcomes for patients with pLGGs, highlighting the importance of the recent breakthroughs in the discovery of targetable lesions.

Personalized Medicine in Brain Gliomas: Targeted Therapy, Patient-Derived Tumor Models (Review)

Gliomas are the most common type of primary malignant brain tumors. The choice of treatments for these tumors was quite limited for many years, and therapy results generally remain still unsatisfactory. Recently, a significant breakthrough in the treatment of many forms of cancer occurred when personalized targeted therapies were introduced which inhibit tumor growth by affecting a specific molecular target. Another trend gaining popularity in oncology is the creation of patient-derived tumor models which can be used for drug screening to select the optimal therapy regimen. Molecular and genetic mechanisms of brain gliomas growth are considered, consisting of individual components which could potentially be exposed to targeted drugs. The results of the literature review show a higher efficacy of the personalized approach to the treatment of individual patients compared to the use of standard therapies. However, many unresolved issues remain in the area of predicting the effectiveness of a particular drug therapy regimen. The main hopes in solving this issue are set on the use of patient-derived tumor models, which can be used in one-stage testing of a wide range of antitumor drugs.

Thromboembolic toxicity observed with concurrent trametinib and lenalidomide therapy

The event-free survival of pediatric low-grade gliomas is poor, and patients often require multiple treatment strategies. While MEK and RAF inhibitors are efficacious in early-phase trials, not all patients respond, and many experience progression following completion of therapy. Evaluating combination therapies that may enhance efficacy or prolong disease stabilization is warranted. We report our institutional experience using concurrent trametinib and lenalidomide in the treatment of primary pediatric central and peripheral nervous system tumors. Two of four patients using this combination therapy experienced severe thromboembolic events, necessitating discontinuation of therapy. This combination requires further investigation, and we urge caution if used.

Co-dependent regulation of p-BRAF and potassium channel KCNMA1 levels drives glioma progression

BRAF mutations have been found in gliomas which exhibit abnormal electrophysiological activities, implying their potential links with the ion channel functions. In this study, we identified the Drosophila potassium channel, Slowpoke (Slo), the ortholog of human KCNMA1, as a critical factor involved in dRaf^GOF glioma progression. Slo was upregulated in dRaf^GOF glioma. Knockdown of slo led to decreases in dRaf^GOF levels, glioma cell proliferation, and tumor-related phenotypes. Overexpression of slo in glial cells elevated dRaf expression and promoted cell proliferation. Similar mutual regulations of p-BRAF and KCNMA1 levels were then recapitulated in human glioma cells with the BRAF mutation. Elevated p-BRAF and KCNMA1 were also observed in HEK293T cells upon the treatment of 20 mM KCl, which causes membrane depolarization. Knockdown KCNMA1 in these cells led to a further decrease in cell viability. Based on these results, we conclude that the levels of p-BRAF and KCNMA1 are co-dependent and mutually regulated. We propose that, in depolarized glioma cells with BRAF mutations, high KCNMA1 levels act to repolarize membrane potential and facilitate cell growth. Our study provides a new strategy to antagonize the progression of gliomas as induced by BRAF mutations.

Low-grade epilepsy-associated neuroepithelial tumors: Tumor spectrum and diagnosis based on genetic alterations

Brain tumors can always result in seizures when involving the cortical neurons or their circuits, and they were found to be one of the most common etiologies of intractable focal seizures. The low-grade epilepsy-associated neuroepithelial tumors (LEAT), as a special group of brain tumors associated with seizures, share common clinicopathological features, such as seizure onsets at a young age, a predilection for involving the temporal lobe, and an almost benign course, including a rather slow growth pattern and thus a long-term history of seizures. Ganglioglioma (GG) and dysembryoplastic neuroepithelial tumor (DNET) are the typical representatives of LEATs. Surgical treatments with complete resection of tumors and related epileptogenic zones are deemed the optimal way to achieve postoperative seizure control and lifetime recurrence-free survival in patients with LEATs. Although the term LEAT was originally introduced in 2003, debates on the tumor spectrum and the diagnosis or classification of LEAT entities are still confusing among epileptologists and neuropathologists. In this review, we would further discuss these questions, especially based on the updated classification of central nervous system tumors in the WHO fifth edition and the latest molecular genetic findings of tumor entities in LEAT entities.

The clinicopathological features of ganglioglioma with CD34 expression and BRAF mutation in patients with epilepsy

Objective

The aim of the study was to evaluate the clinicopathological features, as well as the surgical prognosis, of epilepsy-associated gangliogliomas (GG) with CD34 expression and BRAF^V600E mutation.

Methods

Clinical data of patients who underwent epilepsy surgery for GG were retrospectively studied. Univariate and multivariate analyses were performed to evaluate the correlations of clinical and pathological factors with molecular markers of CD34 expression and BRAF^V600E mutation in GG.

Results

A total of 208 patients with GG had immunohistochemical detection of CD34 expression (positive/negative: 184/24), and among them, 89 patients had immunohistochemical detection of BRAF^V600E mutation (positive/negative: 54/35). By univariate and multivariate analyses, seizure aura (p = 0.025), concordance of ictal electroencephalogram (EEG) findings (p = 0.045) and medial temporal tumor (p = 0.030) were found to be related to CD34 expression, but only hospitalization time (p = 0.042) was different for BRAF-mutated status. In addition, drug-resistant epilepsy (p = 0.040) and concordance of interictal EEG findings (p = 0.009) were found to be associated with tumor progression-free survival (PFS) in univariate analysis, but only concordance of interictal EEG findings was with significance in multivariate analysis. However, CD34 expression or BRAF^V600E mutation in GG was not found to be associated with surgical outcomes of seizure control and tumor PFS.

Conclusion

The CD34 expression or BRAF^V600E mutation in GG may partly influence the distribution of clinicopathological features of patients with epilepsy, but they may be not able to predict the surgical prognosis of seizure outcome and tumor recurrence.

Benign Spinal Tumors

Benign spinal intradural tumors are relatively rare and include intramedullary tumors with a favorable histology such as low-grade astrocytomas and ependymomas, as well as intradural extramedullary tumors such as meningiomas and schwannomas. The effect on the neural tissue is usually a combination of mass effect and neuronal involvement in cases of infiltrative tumors. The new understanding of molecular profiling of different tumors allowed us to better define central nervous system tumors and tailor treatment accordingly. The mainstay of management of many intradural spinal tumors is maximal safe surgical resection. This goal is more achievable with intradural extramedullary tumors; yet, with a meticulous surgical approach, many of the intramedullary tumors are amenable for safe gross-total or near-total resection. The nature of these tumors is benign; hence, a different way to measure outcome success is pursued and usually depends on functional rather than oncological or survival outcomes.

Low-pass whole-genome and targeted sequencing of cell-free DNA from cerebrospinal fluid in pediatric patients with central nervous system tumors

Background

Central nervous system tumors are the most common pediatric solid tumors and the most frequent cause of cancer-related morbidity in childhood. Significant advances in understanding the molecular features of these tumors have facilitated the development of liquid biopsy assays that may aid in diagnosis and monitoring response to therapy. In this report, we describe our comprehensive liquid biopsy platform for detection of genome-wide copy number aberrations, sequence variants, and gene fusions using cerebrospinal fluid (CSF) from pediatric patients with brain, spinal cord, and peripheral nervous system tumors.

Methods

Cell-free DNA was isolated from the CSF from 55 patients, including 47 patients with tumors and 8 controls.

Results

Abnormalities in cell-free DNA were detected in 24 (51%) patients including 11 with copy number alterations, 9 with sequence variants, and 7 with KIAA1549::BRAF fusions. Positive findings were obtained in patients spanning histologic subtypes, tumor grades, and anatomic locations.

Conclusions

This study demonstrates the feasibility of employing this platform in routine clinical care in upfront diagnostic and monitoring settings. Future studies are required to determine the utility of this approach for assessing response to therapy and long-term surveillance.

The landscape of common genetic drivers and DNA methylation in low-grade (epilepsy-associated) neuroepithelial tumors: A review

Low-grade neuroepithelial tumors (LNETs) represent an important group of central nervous system neoplasms, some of which may be associated to epilepsy. The concept of long-term epilepsy-associated tumors (LEATs) includes a heterogenous group of low-grade, cortically based tumors, associated to drug-resistant epilepsy, often requiring surgical treatment. LEATs entities can sometimes be poorly discriminated by histological features, precluding a confident classification in the absence of additional diagnostic tools. This study aimed to provide an updated review on the genomic findings and DNA methylation profiling advances in LNETs, including histological entities of LEATs. A comprehensive search strategy was conducted on PubMed, Embase, and Web of Science Core Collection. High-quality peer-reviewed original manuscripts and review articles with full-text in English, published between 2003 and 2022, were included. Results were screened based on titles and abstracts to determine suitability for inclusion, and when addressed the topic of the review was screened by full-text reading. Data extraction was performed through a qualitative content analysis approach. Most LNETs appear to be driven mainly by a single genomic abnormality and respective affected signaling pathway, including BRAF p.V600E mutations in ganglioglioma, FGFR1 abnormalities in dysembryoplastic neuroepithelial tumor, MYB alterations in angiocentric glioma, BRAF fusions in pilocytic astrocytoma, PRKCA fusions in papillary glioneuronal tumor, between others. However, these molecular alterations are not exclusive, with some overlap amongst different tumor histologies. Also, clustering analysis of DNA methylation profiles allowed the identification of biologically similar molecular groups that sometimes transcend conventional histopathological classification. The exciting developments on the molecular basis of these tumors reinforce the importance of an integrative histopathological and (epi)genetic classification, which can be translated into precision medicine approaches.

Early molecular diagnosis of BRAF status drives the neurosurgical management in BRAF V600E-mutant pediatric low-grade gliomas: a case report

BACKGROUND

To date, this is the only report showing with close and consecutive magnetic resonance images the extremely rapid response of two types of pediatric low-grade gliomas (PLGG) to vemurafenib and its impact on the surgical approach.

CASES PRESENTATION

We report two cases of symptomatic PLGG treated with vemurafenib, a BRAF inhibitor: in a 12-year-old girl it was used as first-line medical treatment, reducing the tumor by 45% within a month and stabilizing to 76% after a year; in a 3-year-old boy with no improvement after SIOP LGG 2004 Protocol, vemurafenib induced in only one week a 34% shrinkage and solved the hydrocephalus, avoiding surgical operation. DISCUSSION AND CONCLUSIONS: Our cases demonstrate how an early molecular diagnosis of BRAF mutations through the neurosurgical biopsy is essential to promptly start targeted therapies., whose effect can influence both therapeutic and surgical decisions, hopefully reducing the occurrence of second neurosurgery with associated risks of neurological sequelae.

The clinical and pathological features of low-grade epilepsy-associated glioneuronal tumors

The aim of the study was to evaluate the clinicopathological features, as well as the surgical prognosis, of epilepsy-associated glioneuronal tumors (GNT) with CD34 expression and BRAF mutation. Clinical data of patients who underwent epilepsy surgery for GNT were retrospectively studied. Univariate and multivariate analyses were performed to evaluate the correlations of clinical and pathological factors with molecular markers of CD34 expression and BRAF^V600E mutation in GNT. A total of 247 patients with GNT had immunohistochemical detection of CD34 expression (CD34 positive vs. negative: 198/49), and among them, 102 patients had immunohistochemical detection of BRAF^V600E mutation (BRAF positive vs. negative: 59/43). Univariate analysis found that tumor types (P < 0.001), patient population (P = 0.015), seizure aura (P = 0.007), drug-resistant epilepsy (P = 0.036), concordance of ictal electroencephalogram (EEG) findings (P = 0.032), surgical resection extent (P = 0.045), tumor location (P = 0.007) and duration of epilepsy (P = 0.027) were related to CD34 expression, and that concordance of ictal EEG findings (P = 0.031) and age at surgery (P = 0.015) were related to BRAF^V600E mutation. In addition, history of generalized tonic-clonic seizure (HR 0.12; P = 0.035), drug-resistant epilepsy (HR 0.13; P = 0.030) and concordance of interictal EEG findings (HR 8.01; P = 0.039) were associated with tumor progression-free survival (PFS). However, CD34 expression or BRAF^V600E mutation in GNT was not associated with surgical outcomes of seizure control and tumor PFS. The CD34 expression or BRAF^V600E mutation in GNT may partly influence the distribution of clinicopathological features of patients with epilepsy, but they may be not able to predict the surgical prognosis of seizure outcome and tumor recurrence.

Small Molecule Inhibitors in Adult High-Grade Glioma: From the Past to the Future

Glioblastoma is the most common primary malignant tumor in the brain and has a dismal prognosis despite patients accepting standard therapies. Alternation of genes and deregulation of proteins, such as receptor tyrosine kinase, PI3K/Akt, PKC, Ras/Raf/MEK, histone deacetylases, poly (ADP-ribose) polymerase (PARP), CDK4/6, branched-chain amino acid transaminase 1 (BCAT1), and Isocitrate dehydrogenase (IDH), play pivotal roles in the pathogenesis and progression of glioma. Simultaneously, the abnormalities change the cellular biological behavior and microenvironment of tumor cells. The differences between tumor cells and normal tissue become the vulnerability of tumor, which can be taken advantage of using targeted therapies. Small molecule inhibitors, as an important part of modern treatment for cancers, have shown significant efficacy in hematologic cancers and some solid tumors. To date, in glioblastoma, there have been more than 200 clinical trials completed or ongoing in which trial designers used small molecules as monotherapy or combination regimens to correct the abnormalities. In this review, we summarize the dysfunctional molecular mechanisms and highlight the outcomes of relevant clinical trials associated with small-molecule targeted therapies. Based on the outcomes, the main findings were that small-molecule inhibitors did not bring more benefit to newly diagnosed glioblastoma, but the clinical studies involving progressive glioblastoma usually claimed “noninferiority” compared with historical results. However, as to the clinical inferiority trial, similar dosing regimens should be avoided in future clinical trials.

Genetic Alteration Analysis of IDH1, IDH2, CDKN2A, MYB and MYBL1 in Pediatric Low-Grade Gliomas

Objective

To investigate pediatric low-grade gliomas for alterations in IDH1, IDH2, CDKN2A, MYB, and MYBL1.

Materials and Methods

DNA and RNA were extracted from 62 pediatric gliomas. Molecular methods included PCR, RT-PCR, and RNA sequencing; Sanger sequencing was used for validation.

Results

Analysis for hotspot genetic alterations in IDH1 R132 and IDH2 R172 (45 and 33 samples) was negative in all cases. CDKN2A deletions were detected in exons 1 and 2 in 1 (pleomorphic xanthoastrocytoma) sample of 9 samples analyzed. Of 10 samples analyzed for MYB translocation, 4 each were positive for translocations with exon 2 and exon 3 of PCDHGA1. Six samples showed MYBL rearrangement. The lack of IDH1/2 genetic alterations is in accordance with the literature in pediatric tumors. Alterations in MYB, MYBL were recently reported to characterize diffuse grade II, but not grade I, gliomas.

Conclusion

We optimized methods for analyzing gene variations and correlated the findings to pathological grade. The high incidence of MYB and MYBL need further evaluation. We also compared DNA, RNA, and RNA sequencing results for fusion, translocation, and genetic alterations. More accurate identification of the underlying biology of pediatric gliomas has implications for the development of targeted treatment.

Pleomorphic xanthoastrocytoma is a heterogeneous entity with pTERT mutations prognosticating shorter survival

Pleomorphic xanthoastrocytoma (PXA) in its classic manifestation exhibits distinct morphological features and is assigned to CNS WHO grade 2 or grade 3. Distinction from glioblastoma variants and lower grade glial and glioneuronal tumors is a common diagnostic challenge. We compared a morphologically defined set of PXA (histPXA) with an independent set, defined by DNA methylation analysis (mcPXA). HistPXA encompassed 144 tumors all subjected to DNA methylation array analysis. Sixty-two histPXA matched to the methylation class mcPXA. These were combined with the cases that showed the mcPXA signature but had received a histopathological diagnosis other than PXA. This cohort constituted a set of 220 mcPXA. Molecular and clinical parameters were analyzed in these groups. Morphological parameters were analyzed in a subset of tumors with FFPE tissue available. HistPXA revealed considerable heterogeneity in regard to methylation classes, with methylation classes glioblastoma and ganglioglioma being the most frequent mismatches. Similarly, the mcPXA cohort contained tumors of diverse histological diagnoses, with glioblastoma constituting the most frequent mismatch. Subsequent analyses demonstrated the presence of canonical pTERT mutations to be associated with unfavorable prognosis among mcPXA. Based on these data, we consider the tumor type PXA to be histologically more varied than previously assumed. Histological approach to diagnosis will predominantly identify cases with the established archetypical morphology. DNA methylation analysis includes additional tumors in the tumor class PXA that share similar DNA methylation profile but lack the typical morphology of a PXA. DNA methylation analysis also assist in separating other tumor types with morphologic overlap to PXA. Our data suggest the presence of canonical pTERT mutations as a robust indicator for poor prognosis in methylation class PXA.

Heterogeneity and excitability of BRAF V600E-induced tumors is determined by Akt/mTOR-signaling state and Trp53-loss

Background

Developmental brain tumors harboring BRAF^V600E somatic mutation are diverse. Here, we describe molecular factors that determine BRAF^V600E-induced tumor biology and function.

Methods

Intraventricular in utero electroporation in combination with the piggyBac transposon system was utilized to generate developmental brain neoplasms, which were comprehensively analyzed with regard to growth using near-infrared in-vivo imaging, transcript signatures by RNA sequencing, and neuronal activity by multielectrode arrays.

Results

BRAF  ^V600E expression in murine neural progenitors elicits benign neoplasms composed of enlarged dysmorphic neurons and neoplastic astroglia recapitulating ganglioglioma (GG) only in concert with active Akt/mTOR-signaling. Purely glial tumors resembling aspects of polymorphous low-grade neuroepithelial tumors of the young (PLNTYs) emerge from BRAF^V600E alone. Additional somatic Trp53-loss is sufficient to generate anaplastic GGs (aGGs) with glioneuronal clonality. Functionally, only BRAF^V600E/pAkt tumors intrinsically generate substantial neuronal activity and show enhanced relay to adjacent tissue conferring high epilepsy propensity. In contrast, PLNTY- and aGG models lack significant spike activity, which appears in line with the glial differentiation of the former and a dysfunctional tissue structure combined with reduced neuronal transcript signatures in the latter.

Conclusion

mTOR-signaling and Trp53-loss critically determine the biological diversity and electrical activity of BRAF^V600E-induced tumors.

Treatment of BRAF V600E mutated ganglioglioma of the third ventricle with dabrafenib

Background:

Ganglioglioma (GG) of the third ventricle is rare. Surgical excision of tumors in this location is associated with high morbidity due to nearby eloquent brain centers. Alternative treatments, when available, should be considered to reduce risks of surgical treatment.

Case Description:

We present the case of a 21-year-old female diagnosed with a BRAF V600E mutated GG of the third ventricle. After an endoscopic biopsy and insertion of a ventriculoperitoneal shunt, the patient was started on the BRAF inhibitor dabrafenib, as an alternative to surgery or radiation. Nearly 2 years after starting dabrafenib, her tumor appearance on serial magnetic resonance imaging is stable, and she has maintained a good quality of life with no new neurological symptoms.

Conclusion:

The disease control thus far suggests targeted medical therapy of GG of the third ventricle with BRAF inhibitors may have efficacy and should be a considered treatment modality.

The multifaceted NF-kB: are there still prospects of its inhibition for clinical intervention in pediatric central nervous system tumors?

Despite advances in the understanding of the molecular mechanisms underlying the basic biology and pathogenesis of pediatric central nervous system (CNS) malignancies, patients still have an extremely unfavorable prognosis. Over the years, a plethora of natural and synthetic compounds has emerged for the pharmacologic intervention of the NF-kB pathway, one of the most frequently dysregulated signaling cascades in human cancer with key roles in cell growth, survival, and therapy resistance. Here, we provide a review about the state-of-the-art concerning the dysregulation of this hub transcription factor in the most prevalent pediatric CNS tumors: glioma, medulloblastoma, and ependymoma. Moreover, we compile the available literature on the anti-proliferative effects of varied NF-kB inhibitors acting alone or in combination with other therapies in vitro, in vivo, and clinical trials. As the wealth of basic research data continues to accumulate, recognizing NF-kB as a therapeutic target may provide important insights to treat these diseases, hopefully contributing to increase cure rates and lower side effects related to therapy.

Integrated genotype-phenotype analysis of long-term epilepsy-associated ganglioglioma

The BRAF p.V600E mutation is the most common genetic alteration in ganglioglioma (GG). Herein, we collected a consecutive series of 30 GG specimens from Xuanwu Hospital in order to corroborate the genetic landscape and genotype–phenotype correlation of this enigmatic and often difficult‐to‐classify epilepsy‐associated brain tumor entity. All specimens with histopathologically confirmed lesions were submitted to targeted next‐generation sequencing using a panel of 131 genes. Genetic alterations in three cases with histologically distinct tumor components, that is, GG plus pleomorphic xanthoastrocytoma (PXA), dysembryoplastic neuroepithelial tumor (DNT), or an oligodendroglioma (ODG)‐like tumor component, were separately studied. A mean post‐surgical follow‐up time‐period of 23 months was available in 24 patients. Seventy seven percent of GG in our series can be explained by genetic alterations, with BRAF p.V600E mutations being most prevalent (n = 20). Three additional cases showed KRAS p.Q22R and KRAS p.G13R, IRS2 copy number gain (CNG) and a KIAA1549‐BRAF fusion. When genetically studying different histopathology patterns from the same tumor we identified composite features with BRAF p.V600E plus CDKN2A/B homozygous deletion in a GG with PXA features, IRS2 CNG in a GG with DNT features, and a BRAF p.V600E plus CNG of chromosome 7 in a GG with ODG‐like features. Follow‐up revealed no malignant tumor progression but nine patients had seizure recurrence. Eight of these nine GG were immunoreactive for CD34, six patients were male, five were BRAF wildtype, and atypical histopathology features were encountered in four patients, that is, ki‐67 proliferation index above 5% or with PXA component. Our results strongly point to activation of the MAP kinase pathway in the vast majority of GG and their molecular‐genetic differentiation from the cohort of low‐grade pediatric type diffuse glioma remains, however, to be further clarified. In addition, histopathologically distinct tumor components accumulated different genetic alterations suggesting collision or composite glio‐neuronal GG variants.

Our results strongly point to activation of the MAP kinase pathway in the vast majority of ganglioglioma (GG).

Composite genetic alterations were found in cases with histologically distinct tumor components firstly, i.e. GG plus pleomorphic xanthoastrocytoma (PXA), dysembryoplastic neuroepithelial tumor, or an oligodendroglioma‐like tumor.

Seizure recurrence is inclined to ganglioglioma with atypical histopathology features (i.e. GG containing a ki‐67 proliferation index above 5% or GG with PXA component).

A novel histopathological grading system for ganglioglioma

Gangliogliomas are central nervous system tumors located in the temporal lobe of young patients, frequently associated with epilepsy. In this paper, we propose a grading system based solely on histopathological criteria. We reevaluated all cases of ganglioglioma, atypical ganglioglioma, and anaplastic ganglioglioma diagnosed between 2011 and 2020 in the Pathology Department of the Emergency Clinical Hospital Bagdasar-Arseni, based on the type of glial mitoses, the number of neuronal and glial mitoses, presence of necrosis, microvascular proliferation, eosinophilic granular bodies, hypercellularity, presence and disposition of inflammatory infiltrate and atypical pleomorphism. Based on the proposed grading system, a score of 0–4 corresponded to a benign ganglioglioma, 5–9 to an atypical ganglioglioma, and 10–18 to an anaplastic ganglioglioma. The survival rates were 90% for benign ganglioglioma, 71.43% for atypical ganglioglioma, and 62.54% for anaplastic ganglioglioma. One case of benign ganglioglioma underwent a malignant transformation into anaplastic ganglioglioma, and recurrences were noticed in 28.57% of atypical ganglioglioma cases and 30.7% of all anaplastic gangliogliomas. The presence of rare glial mitoses and hypercellularity was correlated with mortality in cases of atypical ganglioglioma. We believe this histopathological scoring system could be used as a three-tier system to identify atypical ganglioglioma cases that are bound to have an aggressive course of evolution and require close follow-up. The other option would be to convert it to a two-tier grading system that can separate low-grade gangliogliomas from high-grade ones. The latter category can encompass both atypical and anaplastic ganglioglioma due to the high mortality of both entities.

[Combination of tumors of different histogenesis in pediatric neurosurgery]

Multiple gliomas are determined by synchronous two or more tumors located in different brain regions. It is important to distinguish multiple primary tumors and metastatic brain lesion. In the first case, tumor spread can`t be explained by dissemination along the cerebrospinal fluid pathways, commissural fibers or local metastases. Multiple primary tumors with different histological structures are called bidermal neoplasms. Surgery is preferred in these patients with severe symptoms. The purpose of surgery is maximum resection of tumor. Follow-up may be advisable for small tumors without clinical manifestations. Treatment of multiple gliomas includes surgery, radiotherapy and chemotherapy. Multiple tumor process in children is much more severe compared to a single neoplasia that requires neurological and neuroimaging control and determines treatment strategy. The authors report 3 children with multicentric gliomas, discuss the various aspects of diagnosis and treatment of multiple gliomas and formulate the recommendations for the treatment based on own clinical experience and literature data.

A role for sustained MAPK activity in the mouse ventral telencephalon

The MAPK pathway is a major growth signal that has been implicated during the development of progenitors, neurons, and glia in the embryonic brain. Here, we show that the MAPK pathway plays an important role in the generation of distinct cell types from progenitors in the ventral telencephalon. Our data reveal that phospho-p44/42 (called p-ERK1/2) and the ETS transcription factor Etv5, both downstream effectors in the MAPK pathway, show a regional bias in expression during ventral telencephalic development, with enriched expression in the dorsal region of the LGE and ventral region of the MGE at E13.5 and E15.5. Interestingly, expression of both factors becomes more uniform in ventricular zone (VZ) progenitors by E18.5. To gain insight into the role of MAPK activity during progenitor cell development, we used a cre inducible constitutively active MEK1 allele (Rosa^MEK1DD/+) in combination with a ventral telencephalon enriched cre (Gsx2e-cre) or a dorsal telencephalon enriched cre (Emx1^cre/+). Sustained MEK/MAPK activity in the ventral telencephalon (Gsx2e-cre; Rosa^MEK1DD/+) expanded dorsal lateral ganglionic eminence (dLGE) enriched genes (Gsx2 and Sp8) and oligodendrocyte progenitor cell (OPC) markers (Olig2, Pdgfrα, and Sox10), and also reduced markers in the ventral (v) LGE domain (Isl1 and Foxp1). Activation of MEK/MAPK activity in the dorsal telencephalon (Emx1^cre/+; Rosa^MEK1DD/+) did not initially activate the expression of dLGE or OPC genes at E15.5 but ectopic expression of Gsx2 and OPC markers were observed at E18.5. These results support the idea that MAPK activity as readout by p-ERK1/2 and Etv5 expression is enriched in distinct subdomains of ventral telencephalic progenitors during development. In addition, sustained activation of the MEK/MAPK pathway in the ventral or dorsal telencephalon influences dLGE and OPC identity from progenitors.

Update on Circumscribed Gliomas and Glioneuronal Tumors

Well-circumscribed intra-axial CNS tumors encompass a wide variety of gliomas and glioneuronal tumors, usually corresponding to WHO grades I and II. Nonetheless, sometimes high-grade 'diffuse' gliomas such as gliosarcoma and giant cell glioblastoma can be relatively circumscribed but are often found to have foci of diffuse infiltration on careful examination, harboring distinct molecular alterations. These tumors are excluded from the discussion in this chapter with the current review emphasizing on lower-grade entities to include a brief description of their histology and associated molecular findings. Like elsewhere in brain biopsy evaluation, imaging is crucial and acts as a surrogate to gross examination. Given the circumscribed nature of these tumors, surgery alone is the mainstay treatment in most entities.

Recent Advances in Understanding the Role of Autophagy in Paediatric Brain Tumours

Autophagy is a degradative process occurring in eukaryotic cells to maintain homeostasis and cell survival. After stressful conditions including nutrient deprivation, hypoxia or drugs administration, autophagy is induced to counteract pathways that could lead to cell death. In cancer, autophagy plays a paradoxical role, acting both as tumour suppressor—by cleaning cells from damaged organelles and inhibiting inflammation or, alternatively, by promoting genomic stability and tumour adaptive response—or as a pro-survival mechanism to protect cells from stresses such as chemotherapy. Neural-derived paediatric solid tumours represent a variety of childhood cancers with unique anatomical location, cellular origins, and clinical presentation. These tumours are a leading cause of morbidity and mortality among children and new molecular diagnostics and therapies are necessary for longer survival and reduced morbidity. Here, we review advances in our understanding of how autophagy modulation exhibits antitumor properties in experimental models of paediatric brain tumours, i.e., medulloblastoma (MB), ependymoma (EPN), paediatric low-grade and high-grade gliomas (LGGs, HGGs), atypical teratoid/rhabdoid tumours (ATRTs), and retinoblastoma (RB). We also discuss clinical perspectives to consider how targeting autophagy may be relevant in these specific paediatric tumours.

Mutation-based clustering and classification analysis reveals distinctive age groups and age-related biomarkers for glioma

BACKGROUND

Malignant brain tumor diseases exhibit differences within molecular features depending on the patient's age.

METHODS

In this work, we use gene mutation data from public resources to explore age specifics about glioma. We use both an explainable clustering as well as classification approach to find and interpret age-based differences in brain tumor diseases. We estimate age clusters and correlate age specific biomarkers.

RESULTS

Age group classification shows known age specifics but also points out several genes which, so far, have not been associated with glioma classification.

CONCLUSIONS

We highlight mutated genes to be characteristic for certain age groups and suggest novel age-based biomarkers and targets.

CNS Low-grade Diffusely Infiltrative Tumors With INI1 Deficiency, Possessing a High Propensity to Progress to Secondary INI1-deficient Rhabdoid Tumors

Atypical teratoid/rhabdoid tumors (AT/RTs) are highly malignant tumors of the central nervous system that predominantly occur in infants, and are characterized by the presence of rhabdoid cells and inactivation of INI1 or (rarely) BRG1. Most AT/RT are identified as primary tumors; however, rare AT/RT or INI1-deficient RTs arising from other primary tumors have been reported. Here, we report 3 cases of hitherto unclassifiable low-grade tumors with loss of INI1 nuclear expression, for which we propose the designation of central nervous system low-grade diffusely infiltrative tumors with INI1 deficiency (CNS LGDIT-INI1), 2 of which progressed to secondary RT. All 3 CNS LGDIT-INI1 exhibited a similar histology: diffusely distributed small tumor cells with round to oval or irregular nuclei and scant cytoplasm were admixed with degenerative neurons and large reactive astrocytes in an edematous, myxoid, or collagenous background. Mitotic figures were absent. Immunohistochemistry revealed that the tumor cells in all 3 CNS LGDIT-INI1 and 2 RT were negative for INI1. Genetically, total or partial homozygous deletions of the INI1 gene were detected in all CNS LGDIT-INI1 and RT excluding 1 CNS LGDIT-INI1 without sufficient DNA quality and quantity. Despite the loss of INI1 expression, these low-grade lesions were clearly distinguishable from AT/RT by their low proliferative activity, diffusely infiltrative growth pattern, and lack of rhabdoid cells and polyphenotypic immunoreactivity. In conclusion, CNS LGDIT-INI1 may represent a rare group of tumors that are clinically indolent but have a high propensity to progress to RT.

Efficacy and Safety of Dabrafenib in Pediatric Patients with BRAF V600 Mutation-Positive Relapsed or Refractory Low-Grade Glioma: Results from a Phase I/IIa Study

PURPOSE

Pediatric low-grade glioma (pLGG) is the most prevalent childhood brain tumor. Patients with BRAF V600 mutation-positive pLGG may benefit from treatment with dabrafenib. Part 2 of a phase I/IIa study, open-label study (NCT01677741) explores the activity and safety of dabrafenib treatment in these patients.

PATIENTS AND METHODS

Patients ages 1 to <18 years who had BRAF V600-mutant solid tumors (≥1 evaluable lesion) with recurrent, refractory, or progressive disease after ≥1 standard therapy were treated with oral dabrafenib 3.0 to 5.25 mg/kg/day (part 1) or at the recommended phase II dose (RP2D; part 2). Primary objectives were to determine the RP2D (part 1, results presented in a companion paper) and assess clinical activity (part 2). Here, we report the clinical activity, including objective response rates (ORRs) using Response Assessment in Neuro-Oncology criteria and safety across parts 1 and 2.

RESULTS

Overall, 32 patients with pLGG were enrolled (part 1, n = 15; part 2, n = 17). Minimum follow-up was 26.2 months. Among all patients, the ORR was 44% [95% confidence interval (CI), 26-62] by independent review. The 1-year progression-free survival rate was 85% (95% CI, 64-94). Treatment-related adverse events (AE) were reported in 29 patients (91%); the most common was fatigue (34%). Grade 3/4 treatment-related AEs were reported in 9 patients (28%).

CONCLUSIONS

Dabrafenib demonstrated meaningful clinical activity and acceptable tolerability in patients with BRAF V600-mutant pLGG.

Multidisciplinary Therapy Managed Recurrent Glioblastoma in a BRAF-V600E Mutant Pregnant Female: A Case Report and Review of the Literature

Background: Glioblastoma (GBM) is the most malignant intracranial tumor in adults. However, the overall management of GBM in pregnancy is rarely reported. How to balance the therapeutic benefits to the mother and risks to the fetus remains hugely challenging for clinicians. The application of specific targeting therapy combined with conventional treatment sheds light on a longer lifetime for the patients suffering from GBM. Case Presentation: We present a pregnant female at 20 weeks gestation diagnosed with GBM. Surgical resection was initially performed without adjuvant therapy, and the tumor recurred de novo 2 months later. A secondary craniotomy and cesarean section were performed simultaneously at 32 weeks gestation, both the patient and infant were survived. She was subsequently treated with traditional chemo-radiotherapy. No other identified genetic alterations indicating an optimistic prognosis were detected except for BRAF V600E mutation. Thus, the BRAF inhibitor was placed on her with achieving a good clinical outcome of more than 2-year survival without recurrence. Conclusion: Personalized multidisciplinary therapy should be considered when GBMs occur in pregnancy. Response to the therapy in this presenting case suggests that BRAF V600E mutation is a favorable biomarker for GBM. The mortality of GBM might be reduced through genetic testing and targeted treatment. However, more studies must be conducted to confirm our observation.

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 and molecular characterization of a multi-institutional cohort of pediatric spinal cord low-grade gliomas

Background

The mitogen-activated protein kinases/extracelluar signal-regulated kinases pathway is involved in cell growth and proliferation, and mutations in BRAF have made it an oncogene of interest in pediatric cancer. Previous studies found that BRAF mutations as well as KIAA1549–BRAF fusions are common in intracranial low-grade gliomas (LGGs). Fewer studies have tested for the presence of these genetic changes in spinal LGGs. The aim of this study was to better understand the prevalence of BRAF and other genetic aberrations in spinal LGG.

Methods

We retrospectively analyzed 46 spinal gliomas from patients aged 1–25 years from Children’s Hospital Colorado (CHCO) and The Hospital for Sick Children (SickKids). CHCO utilized a 67-gene panel that assessed BRAF and additionally screened for other possible genetic abnormalities of interest. At SickKids, BRAF^V600E was assessed by droplet digital polymerase chain reaction and immunohistochemistry. BRAF fusions were detected by fluorescence in situ hybridization, reverse transcription polymerase chain reaction, or NanoString platform. Data were correlated with clinical information.

Results

Of 31 samples with complete fusion analysis, 13 (42%) harbored KIAA1549–BRAF. All 13 (100%) patients with confirmed KIAA1549–BRAF survived the entirety of the study period (median [interquartile range] follow-up time: 47 months [27–85 months]) and 15 (83.3%) fusion-negative patients survived (follow-up time: 37.5 months [19.8–69.5 months]). Other mutations of interest were also identified in this patient cohort including BRAF^V600E, PTPN11, H3F3A, TP53, FGFR1, and CDKN2A deletion.

Conclusion

KIAA1549–BRAF was seen in higher frequency than BRAF^V600E or other genetic aberrations in pediatric spinal LGGs and experienced lower death rates compared to KIAA1549–BRAF negative patients, although this was not statistically significant.

Advances in the molecular classification of pediatric brain tumors: a guide to the galaxy

Central nervous system (CNS) tumors are the most common solid tumor in pediatrics, accounting for approximately 25% of all childhood cancers, and the second most common pediatric malignancy after leukemia. CNS tumors can be associated with significant morbidity, even those classified as low grade. Mortality from CNS tumors is disproportionately high compared to other childhood malignancies, although surgery, radiation, and chemotherapy have improved outcomes in these patients over the last few decades. Current therapeutic strategies lead to a high risk of side effects, especially in young children. Pediatric brain tumor survivors have unique sequelae compared to age-matched patients who survived other malignancies. They are at greater risk of significant impairment in cognitive, neurological, endocrine, social, and emotional domains, depending on the location and type of the CNS tumor. Next-generation genomics have shed light on the broad molecular heterogeneity of pediatric brain tumors and have identified important genes and signaling pathways that serve to drive tumor proliferation. This insight has impacted the research field by providing potential therapeutic targets for these diseases. In this review, we highlight recent progress in understanding the molecular basis of common pediatric brain tumors, specifically low-grade glioma, high-grade glioma, ependymoma, embryonal tumors, and atypical teratoid/rhabdoid tumor (ATRT). © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

BRAF V600E mutant oligodendroglioma-like tumors with chromosomal instability in adolescents and young adults

We performed genome-wide methylation analysis on 136 pediatric low-grade gliomas, identifying a unique cluster consisting of three tumors with oligodendroglioma-like histology, BRAF p.V600E mutations and recurrent whole chromosome gains of 7 and loss of 10. Morphologically, all showed similar features, including a diffusely infiltrative glioma composed of round nuclei with perinuclear halos, a chicken-wire pattern of branching capillaries and microcalcification. None showed astrocytic features or characteristics suggestive of high-grade tumors including necrosis or mitotic figures. All tumors harbored multiple chromosomal copy number abnormalities (>10 chromosomes altered), but none showed 1p/19q co-deletion or IDH1 p.R132H mutation. Hierarchical clustering and t-stochastic neighbor embedding analyses from DNA methylation data cluster them more closely to previously described pediatric-type low-grade gliomas and separate from adult gliomas. These tumors exhibit distinct clinical features; they are temporal lobe lesions occurring in adolescents and young adults with a prolonged history of seizures and all are alive with no recurrence (follow-up 3.2 to 13.2 years). We encountered another young adult case with quite similar pathological appearance and molecular status except for TERT promoter mutation. Although the series is small, these may represent a new category of IDH wild-type low-grade gliomas which may be confused with "molecular GBM." Further, they highlight the heterogeneity of IDH wild-type gliomas and the relatively indolent behavior of "pediatric-type" gliomas.

Integrated Molecular and Clinical Analysis of 1,000 Pediatric Low-Grade Gliomas

Pediatric low-grade gliomas (pLGG) are frequently driven by genetic alterations in the RAS-mitogen-activated protein kinase (RAS/MAPK) pathway yet show unexplained variability in their clinical outcome. To address this, we characterized a cohort of >1,000 clinically annotated pLGG. Eighty-four percent of cases harbored a driver alteration, while those without an identified alteration also often exhibited upregulation of the RAS/MAPK pathway. pLGG could be broadly classified based on their alteration type. Rearrangement-driven tumors were diagnosed at a younger age, enriched for WHO grade I histology, infrequently progressed, and rarely resulted in death as compared with SNV-driven tumors. Further sub-classification of clinical-molecular correlates stratified pLGG into risk categories. These data highlight the biological and clinical differences between pLGG subtypes and opens avenues for future treatment refinement.

Pediatric low-grade glioma in the era of molecular diagnostics

Low grade gliomas are the most frequent brain tumors in children and encompass a spectrum of histologic entities which are currently assigned World Health Organisation grades I and II. They differ substantially from their adult counterparts in both their underlying genetic alterations and in the infrequency with which they transform to higher grade tumors. Nonetheless, children with low grade glioma are a therapeutic challenge due to the heterogeneity in their clinical behavior – in particular, those with incomplete surgical resection often suffer repeat progressions with resultant morbidity and, in some cases, mortality. The identification of up-regulation of the RAS–mitogen-activated protein kinase (RAS/MAPK) pathway as a near universal feature of these tumors has led to the development of targeted therapeutics aimed at improving responses while mitigating patient morbidity. Here, we review how molecular information can help to further define the entities which fall under the umbrella of pediatric-type low-grade glioma. In doing so we discuss the specific molecular drivers of pediatric low grade glioma and how to effectively test for them, review the newest therapeutic agents and their utility in treating this disease, and propose a risk-based stratification system that considers both clinical and molecular parameters to aid clinicians in making treatment decisions.

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.

Rapid fully-automated assay for routine molecular diagnosis of BRAF mutations for personalized therapy of low grade gliomas

Background: BRAF mutation analysis is important to personalize the management with low-grade gliomas (LGG) in children and adults, with therapeutic and prognostic impacts. In recurrent tumors, targeted therapies such as BRAF inhibitors had been reported to induce disease stabilization and significant radiographic responses. This highlights the potential interest of BRAF mutation to stratify patients for targeted therapy. Standard operating procedures (SOP) for BRAF V600E mutation detection can be time-consuming and consequently delay treatment choice in patients with acute deterioration. Here, we evaluated Idylla^TM fully automated PCR (FA-PCR) assay for the rapid determination of BRAF mutational status in children and adult LGG.Methods: Formalin-fixed and paraffin-embedded (FFPE) samples from three histological LGG subtypes (ganglioglioma, pleomorphic xantoastrocytoma, and dysembryoplastic neuroepithelial tumor) with previous SOP-characterized BRAF mutational status were re-analyzed using the FA-PCR. Overall concordance with the mutational status determined using SOP, as well as sensitivity and specificity of FA-PCR technique were assessed.Results: All 14 samples gave interpretable results with FA-PCR. Overall concordance of BRAF mutational status between FA-PCR and SOP was 100%. Sensitivity and specificity were 100%.Conclusion: This study confirms the reliability of FA-PCR for BRAF mutations analysis in children and adult LGG. Considering the short time to results enabled by FA-PCR, providing results in less than 90 minutes, this technique represents an interesting option for the molecular diagnosis of LGG and personalization of treatment.

PD-L1 Expression in Pediatric Low-Grade Gliomas Is Independent of BRAF V600E Mutational Status

To evaluate a potential relationship between BRAF V600E mutation and PD-L1 expression, we examined the expression of PD-L1 in pediatric high- and low-grade glioma cell lines as well as a cohort of pediatric low-grade glioma patient samples. Half of the tumors in our patient cohort were V600-wildtype and half were V600E mutant. All tumors expressed PD-L1. In most tumors, PD-L1 expression was low (<5%), but in some cases over 50% of cells were positive. Extent of PD-L1 expression and immune cell infiltration was independent of BRAF V600E mutational status. All cell lines evaluated, including a BRAF V600E mutant xenograft, expressed PD-L1. Transient transfection of cell lines with a plasmid expressing mutant BRAF V600E had minimal effect on PD-L1 expression. These findings suggest that the PD-1 pathway is active in subsets of pediatric low-grade glioma as a mechanism of immune evasion independent of BRAF V600E mutational status. Low-grade gliomas that are unresectable and refractory to traditional therapy are associated with significant morbidity and continue to pose a treatment challenge. PD-1 pathway inhibitors may offer an alternative treatment approach. Clinical trials will be critical in determining whether PD-L1 expression indicates likely therapeutic benefit with immune checkpoint inhibitors.

A Phase I and Pharmacokinetic Study of Oral Dabrafenib in Children and Adolescent Patients with Recurrent or Refractory BRAF V600 Mutation-Positive Solid Tumors

PURPOSE

The 2-part, phase I/IIa, open-label study (NCT01677741) sought to determine the safety, tolerability, pharmacokinetics, and preliminary activity of dabrafenib in pediatric patients with advanced BRAF V600-mutated cancers.

PATIENTS AND METHODS

This phase I dose-finding part treated patients ages 1 to <18 years with BRAF V600 mutation-positive tumors with oral dabrafenib 3 to 5.25 mg/kg/day to determine the RP2D based on safety and drug exposure target.

RESULTS

Between May 2013 and November 2014, 27 patients [12 male; median age, 9 years (range, 1-17 years)] with BRAF V600-mutant solid tumors recurrent/refractory to treatment (low- or high-grade glioma, Langerhans cell histiocytosis, neuroblastoma, or thyroid cancer) were enrolled. The median treatment duration was 75.6 weeks (range, 5.6-148.7 weeks), with 63% treated for >52 weeks and 52% undergoing treatment at data cutoff date. The most common grade 3/4 adverse events suspected to be related to study drug were maculopapular rash and arthralgia (2 patients each). No dose-limiting toxicities were observed. Pharmacokinetic analyses showed a dose-dependent increase in AUC0-12 and achievement of adult exposure levels at the recommended phase II doses of 5.25 mg/kg/day (age <12 years) and 4.5 mg/kg/day (age ≥12 years) divided into 2 equal doses daily, not exceeding 300 mg daily.

CONCLUSIONS

In this first clinical trial in pediatric patients with pretreated BRAF V600-mutant tumors, dabrafenib was well tolerated while achieving target exposure levels; the average treatment duration was >1 year with many patients still on treatment. The phase II component is also closed and will be reported separately.

Secondary INI1-deficient rhabdoid tumors of the central nervous system: analysis of four cases and literature review

Atypical teratoid/rhabdoid tumors (AT/RT) are rare, highly malignant neoplasms of the central nervous system that predominantly occur in infants, and are characterized by the presence of rhabdoid cells and inactivation of INI1 or (extremely rarely) BRG1. The vast majority of AT/RT are recognized as primary tumors; however, rare AT/RT or INI1-deficient RT arising from other primary tumors have been reported. To better characterize secondary RT, we performed a histological and molecular analysis of four RT arising from pleomorphic xanthoastrocytoma (PXA), anaplastic PXA, low-grade astrocytoma, or ependymoma. Histologically, although conventional AT/RT are usually not largely composed of rhabdoid cells, three secondary RT were composed mainly of rhabdoid cells, two of which arising from (anaplastic) PXA exhibited marked nuclear pleomorphism reminiscent of that in the precursor lesions. Regarding INI1 alterations, although mutations including small indels are frequent in conventional AT/RT, only in one secondary RT had a mutation. Moreover, together with previously reported cases, biallelic INI1 inactivation in secondary RT was mostly due to biallelic focal and/or broad deletions. Although conventional AT/RT have stable chromosomal profiles, i.e., the frequency of copy number changes involving chromosomes other than chromosome 22 is remarkably low, our array comparative genomic hybridization analysis revealed numerous copy number changes in the secondary RT. In conclusion, secondary RT of the central nervous system are clinicopathologically and molecularly different from conventional pediatric AT/RT, and a nosological issue is whether these secondary RT should be called secondary "AT/RT" as most of the reported cases were.

The Rare Phenomenon of Loss of INI1 Expression at Recurrence/Progression of Primary Central Nervous System Tumors: Report of 3 Cases

It is extremely rare for loss of immunohistochemical expression of INI1 to occur primarily at recurrence/progression with retained expression at the primary/initial presentation of central nervous system (CNS) tumor. In this article, we present 3 such cases showing loss of INI1 expression primarily at recurrence. All patients were males, aged 7 years (case 1), 11 years (case 2), and 35 years (case 3), diagnosed with low-grade glial/glioneuronal tumor, not otherwise specified (case 1), craniopharyngioma (case 2), and glioblastoma (case 3); all showed retained INI1 protein expression. Case 1 at 12 months recurrence showed a high-grade tumor with relative undifferentiated morphology, case 2 after 104 months showed a sarcomatous progression, and case 3 recurred after 4 months with the presence of relative undifferentiated round cells. All these recurrences showed loss of INI1 expression. Loss of SMARCB1/INI1 gene function resulting in complete loss of INI1 protein expression is not a well-accepted genetic mechanism for transformation/progression as this series emphasizes.

Pediatric ganglioglioma of the brainstem and cervicomedullary junction: a retrospective cohort study

OBJECTIVE

Ganglioglioma is a low-grade central nervous system neoplasm with a pediatric predominance, accounting for 10% of all brain tumors in children. Gangliogliomas of the cervicomedullary junction (GGCMJs) and brainstem (GGBSs) present a host of management challenges, including a significant risk of surgical morbidity. At present, understanding of the prognostic factors-including BRAF V600E status-is incomplete. Here, the authors report a single-institution GGCMJ and GGBS experience and review the pertinent literature.

METHODS

A prospectively maintained neurosurgical database at a large tertiary care academic referral center was retrospectively queried for cases of GGCMJ pathologically confirmed in the period from 1995 to 2015; appropriate cases were defined by diagnosis codes and keywords. Secondary supplemental chart review was conducted to confirm or capture relevant data. The primary study outcome was treatment failure as defined by evidence of radiographic recurrence or progression and/or clinical or functional decline. A review of the literature was conducted as well.

RESULTS

Five neurosurgically managed GGBS patients were identified, and the neoplasms in 4 were classified as GGCMJ. All 5 patients were younger than 18 years old (median 15 years, range 4-16 years) and 3 (60%) were female. One patient underwent gross-total resection, 2 underwent aggressive subtotal resection (STR), and 2 underwent stereotactic biopsy only. All patients who had undergone STR or biopsy required repeat resection for tumor control or progression. Progressive disease was treated with radiotherapy in 2 patients, chemotherapy in 2, and chemoradiotherapy alone in 1. Immunostaining for BRAF V600E was positive in 3 patients (60%). All 5 patients experienced at least one major complication, including wound infection, foot drop, hemiparesis, quadriparesis, cranial neuropathy, C2-3 subluxation, syringomyelia, hydrocephalus, aspiration, and coma. Overall mortality was 20%, with 1 death observed over 11 years of follow-up.

CONCLUSIONS

GGBS and GGCMJ are rare, benign posterior fossa tumors that carry significant perioperative morbidity. Contemporary management strategies are heterogeneous and include combinations of resection, radiotherapy, and chemotherapy. The BRAF V600E mutation is frequently observed in GGBS and GGCMJ and appears to have both prognostic and therapeutic significance with targeted biological agents.

A Pediatric Intra-Axial Malignant SMARCB1-Deficient Desmoplastic Tumor Arising in Meningioangiomatosis

SMARCB1 inactivation is a well-established trigger event in atypical teratoid/rhabdoid tumor. Recently, a role for SMARCB1 inactivation has emerged as a mechanism of clonal evolution in other tumor types, including rare brain tumors. We describe an unusual malignant intra-axial SMARCB1-deficient spindle cell desmoplastic neoplasm, occurring in a 6-year-old child with meningioangiomatosis and a long history of seizures. Striking features of the tumor were a storiform pattern and strong CD34 expression. Undifferentiated round cell areas with isolated rhabdoid cells showing high mitotic index and focal necrosis with INI1 expression loss were present. The meningioangiomatosis component showed few chromosomal imbalances, including chromosomal 22 monosomy (where SMARCB1 maps) and gain at 6q14.3. In addition to these abnormalities, the spindle cell desmoplastic neoplasm and its dedifferentiated SMARCB1-deficient component shared several other aberrations, including homozygous deletion at 9p21.3, losses at 1p, 3p, 3q, 10p, and 13q, gains and losses at 5p and 11p. In line with INI1 loss, the dedifferentiated component showed remarkably decreased levels of SMARCB1 transcript. The residual SMARCB1 allele was wildtype. Our findings suggest progression from the meningioangiomatosis to the malignant desmoplastic neoplasm through the occurrence of complex chromosomal abnormalities, and point to functional silencing of SMARCB1 in the dedifferentiation component.