Gliomatosis cerebri: no evidence for a separate brain tumor entity

Revisiting prognostic factors of gliomatosis cerebri in adult-type diffuse gliomas

PURPOSE

There is lack of comprehensive analysis evaluating the impact of clinical, molecular, imaging, and surgical data on survival of patients with gliomatosis cerebri (GC). This study aimed to investigate prognostic factors of GC in adult-type diffuse glioma patients.

METHODS

Retrospective chart and imaging review was performed in 99 GC patients from adult-type diffuse glioma (among 1,211 patients; 6 oligodendroglioma, 16 IDH-mutant astrocytoma, and 77 IDH-wildtype glioblastoma) from a single institution between 2005 and 2021. Predictors of overall survival (OS) of entire patients and IDH-wildtype glioblastoma patients were determined.

RESULTS

The median OS was 16.7 months (95% confidence interval [CI] 14.2-22.2) in entire patients and 14.3 months (95% CI 12.2-61.9) in IDH-wildtype glioblastoma patients. In entire patients, KPS (hazard ratio [HR] = 0.98, P = 0.004), no 1p/19q codeletion (HR = 10.75, P = 0.019), MGMTp methylation (HR = 0.54, P = 0.028), and hemorrhage (HR = 3.45, P = 0.001) were independent prognostic factors on multivariable analysis. In IDH-wildtype glioblastoma patients, KPS (HR = 2.24, P = 0.075) was the only independent prognostic factor on multivariable analysis. In subgroup of IDH-wildtype glioblastoma with CE tumors, total resection of CE tumor did not remain as a significant prognostic factor (HR = 1.13, P = 0.685).

CONCLUSIONS

The prognosis of GC patients is determined by its underlying molecular type and patient performance status. Compared with diffuse glioma without GC, aggressive surgery of CE tumor in GC patients does not improve survival.

Presurgical diagnosis of diffuse gliomas in adults: Post-WHO 2021 practical perspectives from radiologists in neuro-oncology units

The 2021 World Health Organization classification of CNS tumours was greeted with enthusiasm as well as an initial potential overwhelm. However, with time and experience, our understanding of its key aspects has notably improved. Using our collective expertise gained in neuro-oncology units in hospitals in different countries, we have compiled a practical guide for radiologists that clarifies the classification criteria for diffuse gliomas in adults. Its format is clear and concise to facilitate its incorporation into everyday clinical practice. The document includes a historical overview of the classifications and highlights the most important recent additions. It describes the main types in detail with an emphasis on their appearance on imaging. The authors also address the most debated issues in recent years. It will better prepare radiologists to conduct accurate presurgical diagnoses and collaborate effectively in clinical decision making, thus impacting decisions on treatment, prognosis, and overall patient care.

A Novel Type of IDH-wildtype Glioma Characterized by Gliomatosis Cerebri-like Growth Pattern, TERT Promoter Mutation, and Distinct Epigenetic Profile

Diffuse gliomas in adults encompass a heterogenous group of central nervous system neoplasms. In recent years, extensive (epi-)genomic profiling has identified several glioma subgroups characterized by distinct molecular characteristics, most importantly IDH1/2 and histone H3 mutations. A group of 16 diffuse gliomas classified as "adult-type diffuse high-grade glioma, IDH-wildtype, subtype F (HGG-F)" was identified by the DKFZ v12.5 Brain Tumor Classifier . Histopathologic characterization, exome sequencing, and review of clinical data was performed in all cases. Based on unsupervised t -distributed stochastic neighbor embedding and clustering analysis of genome-wide DNA methylation data, HGG-F shows distinct epigenetic profiles separate from established central nervous system tumors. Exome sequencing demonstrated frequent TERT promoter (12/15 cases), PIK3R1 (11/16), and TP53 mutations (5/16). Radiologic characteristics were reminiscent of gliomatosis cerebri in 9/14 cases (64%). Histopathologically, most cases were classified as diffuse gliomas (7/16, 44%) or were suspicious for the infiltration zone of a diffuse glioma (5/16, 31%). None of the cases demonstrated microvascular proliferation or necrosis. Outcome of 14 patients with follow-up data was better compared to IDH-wildtype glioblastomas with a median progression-free survival of 58 months and overall survival of 74 months (both P <0.0001). Our series represents a novel type of adult-type diffuse glioma with distinct molecular and clinical features. Importantly, we provide evidence that TERT promoter mutations in diffuse gliomas without further morphologic or molecular signs of high-grade glioma should be interpreted in the context of the clinicoradiologic presentation as well as epigenetic profile and may not be suitable as a standalone marker for glioblastoma, IDH-wildtype.

H3G34-Mutant Gliomas-A Review of Molecular Pathogenesis and Therapeutic Options

The 2021 World Health Organization Classification of Tumors of the Central Nervous System reflected advances in understanding of the roles of oncohistones in gliomagenesis with the introduction of the H3.3-G34R/V mutant glioma to the already recognized H3-K27M altered glioma, which represent the diagnoses of pediatric-type diffuse hemispheric glioma and diffuse midline glioma, respectively. Despite advances in research regarding these disease entities, the prognosis remains poor. While many studies and clinical trials focus on H3-K27M-altered-glioma patients, those with H3.3-G34R/V mutant gliomas represent a particularly understudied population. Thus, we sought to review the current knowledge regarding the molecular mechanisms underpinning the gliomagenesis of H3.3-G34R/V mutant gliomas and the diagnosis, treatment, long-term outcomes, and possible future therapeutics.

An enduring debate on gliomatosis cerebri

Gliomatosis cerebri (GC) is a unique glial tumor that extensively invades the cerebral white matter and has been recognized as an entity of neuroepithelial tumors since the first edition of the WHO classification of brain tumors in 1979. Thereafter, in the fourth edition of the WHO classification in 2007, it was clearly defined as a specific type of astrocytic tumor. However, in the WHO 2016 classification, which was based on the concept of integrated diagnosis using molecular genetics, GC was deleted as it was considered to be only one growth pattern of diffuse glioma and not a specific pathological entity. Since then, there has been criticism by many neuro-oncologists and the establishment of the GC working group at the NIH, and many activities in the world arguing that GC should not be deleted from the clinical discussion of brain tumors. In Japan, positive activities toward multicenter research on GC pathology should be performed, and molecular pathological evidence that can contribute to the WHO classification in the future should be developed. In this article, the author outlined the pathological characteristics of GC, which has been repeated changing since its conception, and also describes his opinion on GC as a neuro-oncologist.

Clinical, Imaging and Neurogenetic Features of Patients with Gliomatosis Cerebri Referred to a Tertiary Neuro-Oncology Centre

INTRODUCTION

Gliomatosis cerebri describes a rare growth pattern of diffusely infiltrating glioma. The treatment options are limited and clinical outcomes remain poor. To characterise this population of patients, we examined referrals to a specialist brain tumour centre.

METHODS

We analysed demographic data, presenting symptoms, imaging, histology and genetics, and survival in individuals referred to a multidisciplinary team meeting over a 10-year period.

RESULTS

In total, 29 patients fulfilled the inclusion criteria with a median age of 64 years. The most common presenting symptoms were neuropsychiatric (31%), seizure (24%) or headache (21%). Of 20 patients with molecular data, 15 had IDH wild-type glioblastoma, with an IDH1 mutation most common in the remainder (5/20). The median length of survival from MDT referral to death was 48 weeks (IQR 23 to 70 weeks). Contrast enhancement patterns varied between and within tumours. In eight patients who had DSC perfusion studies, five (63%) had a measurable region of increased tumour perfusion with rCBV values ranging from 2.8 to 5.7. A minority of patients underwent MR spectroscopy with 2/3 (66.6%) false-negative results.

CONCLUSIONS

Gliomatosis imaging, histological and genetic findings are heterogeneous. Advanced imaging, including MR perfusion, could identify biopsy targets. Negative MR spectroscopy does not exclude the diagnosis of glioma.

Gliomatosis cerebri (GC) growth pattern: A single-center analysis of clinical, histological, and molecular characteristics of GC and non-GC glioblastoma

Background

The biological understanding of glioblastoma (GB) with gliomatosis cerebri (GC) pattern is poor due to the absence of GC-specific studies. Here, we aimed to identify molecular or clinical parameters that drive GC growth.

Methods

From our methylome database of IDH (isocitrate dehydrogenase)-wildtype GB, we identified 158 non-GC and 65 GC cases. GC cases were subdivided into diffuse-infiltrative (subtype 1), multifocal (subtype 2), or tumors with 1 solid mass (subtype 3). We compared clinical, histological, and molecular parameters and conducted a reference-free tumor deconvolution of DNA methylation data based on latent methylation components (LMC).

Results

GC subtype 1 less frequently showed contrast-enhancing tumors, and more frequently lacked morphological GB criteria despite displaying GB DNA methylation profile. However, the tumor deconvolution did not deliver a specific LMC cluster for either of the GC subtypes. Employing the reference-based analysis MethylCIBERSORT, we did not identify significant differences in tumor cell composition. The majority of both GC and non-GC patients received radiochemotherapy as first-line treatment, but there was a major imbalance for resection. The entire GC cohort had significantly shorter overall survival (OS) and time to treatment failure (TTF) than the non-GC cohort. However, when filtering for cases in which only stereotactic biopsy was performed, the comparison of OS and TTF lost statistical significance.

Conclusions

Our study offers clinically relevant information by demonstrating a similar outcome for GB with GC growth pattern in the surgically matched analysis. The limited number of cases in the GC subgroups encourages the validation of our DNA methylation analysis in larger cohorts.

BRAF and MEK Targeted Therapies in Pediatric Central Nervous System Tumors

Simple Summary

This review is divided into two parts. The first analyzes the mechanisms of two important cellular pathways that are involved in tumoral proliferation, differentiation, migration, and angiogenesis: RAS/RAF/MEK/MAPK and PI3K/AKT/mTOR. The second part focuses on the currently available experience regarding targeted therapies against the mitogen-activated protein kinase (MAPK) pathway in pediatric CNS tumors, with the hope of offering a practical guide for consultation.

Abstract

BRAF is a component of the MAPK and PI3K/AKT/mTOR pathways that play a crucial role in cellular proliferation, differentiation, migration, and angiogenesis. Pediatric central nervous system tumors very often show mutations of the MAPK pathway, as demonstrated by next-generation sequencing (NGS), which now has an increasing role in cancer diagnostics. The MAPK mutated pathway in pediatric CNS tumors is the target of numerous drugs, approved or under investigation in ongoing clinical trials. In this review, we describe the main aspects of MAPK and PI3K/AKT/mTOR signaling pathways, with a focus on the alterations commonly involved in tumorigenesis. Furthermore, we reported the main available data about current BRAF and MEK targeted therapies used in pediatric low-grade gliomas (pLLGs), pediatric high-grade gliomas (pHGGs), and other CNS tumors that often present BRAF or MEK mutations. Further molecular stratification and clinical trial design are required for the treatment of pediatric CNS tumors with BRAF and MEK inhibitors.

Radiological Prediction of Isocitrate Dehydrogenase (IDH) Mutational Status and Pathological Verification for Lower-Grade Astrocytomas

Background and objective

The isocitrate dehydrogenase (IDH) status of patients with World Health Organization (WHO) grade II or III astrocytoma is essential for understanding its biological features and determining therapeutic strategies. This study aimed to use radiological analysis to predict the IDH status of patients with lower-grade astrocytomas and to verify the pathological implications.

Methods

In this study, 47 patients with grade II (17 cases) or III astrocytomas (30 cases), based on 2016 WHO Classification, underwent methionine (MET) positron emission tomography (PET) and magnetic resonance spectroscopy (MRS) on the same day between January 2013 and June 2020. The patients were retrospectively assessed. Immunohistochemistry showed 23 cases of IDH-mutant and 24 of IDH-wildtype. Based on fluid-attenuated recovery inversion (FLAIR)/T2 imaging, three doctors blinded to clinical data independently allocated 18 patients to the clear boundary group between the tumor and the normal brain and 29 to the unclear boundary group. The peak ratios of N-acetylaspartate (NAA)/creatine (Cr), choline (Cho)/Cr, and Cho/NAA and the tumor-to-normal region (T/N) ratio for maximum accumulation in MET-PET were calculated. For statistical analysis, Fisher’s exact test was used to assess associations between two variables, and the Mann-Whitney U test to compare the values between the IDH-wildtype and IDH-mutant groups. The optimal cut-off values of MET T/N ratio and MRS parameters for discriminating IDH-wildtype from IDH-mutant were obtained using receiver operating characteristics curves.

Results

The unclear boundary group had significantly more IDH-wildtype cases than the clear boundary group (P<0.001). The IDH-wildtype group had significantly lower Cho/Cr (<1.84) and Cho/NAA (<1.62) ratios (P=0.02 and P=0.047, respectively) and a higher MET T/N ratio (>1.44, P=0.02) than the IDH-mutant group. The odds for the IDH-wildtype were 0.22 for patients who fulfilled none of the four criteria, including boundary status and three ratios, and 0.9 for all four criteria.

Conclusions

These results suggest that the combination of MRI, MRS, and MET-PET examination could be helpful for the prediction of IDH status in WHO grade II/III gliomas.

Leptomeningeal dissemination of anaplastic medullary cone astrocytoma: an unexpected findings in a patient with leptomeningeal enhancement and clinical history of multiple myeloma

We report a challenging autopsy case with an insidious clinical presentation with diffuse lepto- and pachymeningeal enhancement in a context of a complex clinical history. Clinical features, neuroradiological and anamnestic data were consistent with central nervous system (CNS) dissemination of a previously known lambda restricted multiple myeloma. Autoptic findings allowed to discard this hypothesis. Unexpectedly, CNS sampling revealed an atypical glial cell proliferation within the sacral meningeal layers. No primary intraparenchymal CNS glial lesion was found. Findings supported the final diagnosis of anaplastic astrocytoma IDH1-wild type of the medullary cone with diffuse leptomeningeal and cerebrospinal fluid (CSF) dissemination. This occurrence represents an extremely rare condition itself, further complicated by the clinical history of the patient that led to formulate the most probable diagnosis of localization of the primary known disease. This autopsy case underlines that patients previously diagnosed with a primary tumor are not only at risk of recurrences or progression of the original disease, but they must be always accurately checked for eventual onset of a second tumor, including rare conditions such as gliomatosis.

A rare case of gliomatosis cerebri lurking beneath the shadows of a stroke mimic

Gliomatosis cerebri (GC) is a diffuse infiltrative neoplastic glial process with a devastating prognosis. Considering its rarity, unpredictable clinical manifestations, and lack of characteristic radiographic features, GC is a difficult diagnosis that is quite often delayed. In this report, we present a case of a 61-year-old man with a history of chronic alcohol abuse and atrial fibrillation who presented with right arm weakness initially presumed to be from an acute ischemic stroke. GC was not diagnosed until six months after initial symptoms and diagnosis was indicated when considering the neurocognitive findings in conjunction with suggestive radiographic findings. The presence of a rapid, expansile lesion in the cortex, corpus callosum, and infratentorial structures with mild parenchymal enlargement, as shown in our case, is more revealing of an invasive entity typical of GC rather than an ischemic process and other pathologies. This case demonstrates the fatal challenges of its prompt recognition and the therapeutic limitations for those patients presenting with advanced symptoms at the time of diagnosis. Recognizing GC in cases with such rapid multilobe clinical features with similar diffusely invasive patterns of growth on imaging can avoid a delay in diagnosis and improve patient quality of life.

Leber’s hereditary optic neuropathy with diffuse white matter changes mimicking gliomatosis cerebri: illustrative case

BACKGROUIND

Leber’s hereditary optic neuropathy (LHON) is a mitochondrial disease characterized by bilateral severe subacute central vision loss and a mutation in the mitochondrial DNA (mtDNA). The findings on cranial magnetic resonance imaging of patients with LHON vary from subtle to multiple white matter changes. However, they rarely present with diffuse infiltrative white matter changes.

OBSERVATIONS

The authors reported a case with diffuse white matter changes mimicking gliomatosis cerebri (GC). The histological findings included only mild glial hyperplasia without immunohistochemical positivity, supporting the diagnosis of glial tumors. Analysis of mtDNA obtained from the blood and brain tissue revealed mutation of m.11778G>A in the NADH dehydrogenase 4 gene, which confirmed the case as LHON. Immunohistochemistry of the brain tissue revealed 8-hydroxy-2′-deoxyguanosine positivity, suggesting the presence of oxidative stress.

LESSONS

LHON is extremely difficult to diagnose unless one suspects or knows the disease. The present case brings attention not only to LHON but also to other mtDNA-mutated diseases that need to be considered with diffuse white matter changes or GC.

Spinal Cord Diffuse Midline Glioma With Histone H3 K27M Mutation in a Pediatric Patient

Background: Diffuse midline glioma (DMG) with histone H3 K27M mutation is a recently identified entity documented in the 2016 World Health Organization (WHO) Classification of Tumors of the Central Nervous System. Spinal cord DMGs with H3 K27M-mutant are commonly reported in adults. Herein, we reported a pediatric patient with spinal cord H3 K27M-mutant DMG.

Case Report: A 7-year-old girl with 1-month history of neck pain and 3-week history of progressive weakness in the right hand was presented. Spinal magnetic resonance imaging showed an intramedullary lesion with slight enhancement at the C2-7 levels. With intraoperative neuroelectrophysiological monitoring, the lesion was subtotally resected. Histopathological examination revealed a DMG with histone H3 K27M mutation corresponding to WHO grade IV. Postoperatively, the neck pain was relieved, and the upper-extremity weakness remained unchanged. Oral temozolomide was administrated for 7 months, and radiotherapy was performed for 22 courses. After an 18-month follow-up, no tumor recurrence was noted.

Conclusion: Spinal cord H3 K27M-mutant DMGs are extremely rare in pediatric patients. Preoperative differential diagnosis is challenging, and surgical resection with postoperative chemoradiotherapy may be an effective treatment.

High-grade gliomas in adolescents and young adults highlight histomolecular differences from their adult and pediatric counterparts

BACKGROUND

Considering that pediatric high-grade gliomas (HGGs) are biologically distinct from their adult counterparts, the objective of this study was to define the landscape of HGGs in adolescents and young adults (AYAs).

METHODS

We performed a multicentric retrospective study of 112 AYAs from adult and pediatric Ile-de-France neurosurgical units, treated between 1998 and 2013 to analyze their clinicoradiological and histomolecular profiles. The inclusion criteria were age between 15 and 25 years, histopathological HGG diagnosis, available clinical data, and preoperative and follow-up MRI. MRI and tumoral samples were centrally reviewed. Immunohistochemistry and complementary molecular techniques such as targeted/next-generation sequencing, whole exome sequencing, and DNA-methylation analyses were performed to achieve an integrated diagnosis according to the 2016 World Health Organization (WHO) classification.

RESULTS

Based on 80 documented AYA patients, HGGs constitute heterogeneous clinicopathological and molecular groups, with a predominant representation of pediatric subtypes (histone H3-mutants, 40%) but also adult subtypes (isocitrate dehydrogenase [IDH] mutants, 28%) characterized by the rarity of oligodendrogliomas, IDH mutants, and 1p/19q codeletion and the relative high frequency of "rare adult IDH mutations" (20%). H3G34-mutants (14%) represent the most specific subgroup in AYAs. In the H3K27-mutant subgroup, non-brainstem diffuse midline gliomas are more frequent (66.7%) than diffuse intrinsic pontine gliomas (23.8%), contrary to what is observed in children. We found that WHO grade has no prognostic value, but molecular subgrouping has major prognostic importance.

CONCLUSIONS

HGGs in AYAs could benefit from a specific classification, driven by molecular subtyping rather than age group. Collaborative efforts are needed from pediatric and adult neuro-oncology teams to improve the management of HGGs in AYAs.

Gliomatosis Cerebri Growth Pattern: Association of Differential First-Line Treatment with Overall Survival in WHO Grade II and III Gliomas

INTRODUCTION

Gliomatosis cerebri (GC) is defined by diffuse, widespread glial tumor growth affecting three or more cerebral lobes. Previous studies in gliomas found no distinct histological or molecular GC subtype, yet the presence of GC is associated with worse median overall survival (OS). Here, we explored whether differing therapeutic strategies in first-line treatment could account for this.

METHODS

From our University Cancer Center database, 47 patients with histological diagnosis of WHO grade II or III glioma and GC imaging pattern were identified. GC criteria were confirmed by independent review. Patients with WHO grade II or III glioma with non-GC pattern served as control cohort (n = 343).

RESULTS

Within the GC patient cohort, lower WHO grade, mutated isocitrate dehydrogenase 1 (IDH1) status, and absence of contrast enhancement were associated with better OS. Compared to the control cohort, patients with GC had significantly shorter OS independent of histological diagnosis or IDH1 mutation status. Patients with GC preferentially received chemotherapy alone (62 vs. 18%), and less frequently radiochemotherapy (21 vs. 27%). OS was significantly shorter in the GC cohort compared to the non-GC cohort both for chemotherapy (3.9 vs. 7.6 years, p = 0.0085) and for combined radiochemotherapy (1.1 vs. 8.4 years, p < 0.0001). However, when only patients who received biopsy plus chemotherapy were analyzed, the differences lost statistical significance (3.5 vs. 6.6 years, p = 0.196).

CONCLUSION

We found major differences in the selection of first-line therapies of GC versus non-GC patients. Our results suggest that these differences may partly account for the worse prognosis of GC patients.

Canine Gliomatosis Cerebri: Morphologic and Immunohistochemical Characterization Is Supportive of Glial Histogenesis

Gliomatosis cerebri (GC) is a glioma subtype with diffuse neuroparenchymal infiltration without architectural distortion. GC was first used in human neuropathology and remained controversial until its elimination from the diagnostic lexicon in 2016. GC is currently defined as a diffuse growth pattern of glioma rather than a distinct entity. In this article, we characterize 24 cases of canine GC and classify these neoplasms as diffuse gliomas. Selected cases of canine GC were reviewed and immunolabeled for oligodendrocyte lineage transcription factor 2 (Olig2), glial fibrillary acidic protein (GFAP), and 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase). The mean age of affected dogs was 7 years, and 9 were brachycephalic. Gross lesions (8 cases) consisted mainly of parenchymal swelling. Histologically, of the 24 cases, there was widespread infiltration of neoplastic cells with astrocytic (12 cases), oligodendroglial (8 cases), or mixed morphology (4 cases) in the brain (18 cases), spinal cord (4 cases), or both (2 cases). Secondary structures occurred across different tumor grades and were not restricted to high-grade neoplasms. Astrocytic neoplasms had moderate nuclear immunolabeling for Olig2 and robust cytoplasmic immunolabeling for GFAP. Oligodendroglial neoplasms had robust nuclear immunolabeling for Olig2, moderate or absent cytoplasmic immunolabeling for GFAP, and moderate cytoplasmic immunolabeling for CNPase. Tumors with mixed morphology had robust nuclear immunolabeling for Olig2 and variable cytoplasmic immunolabeling for GFAP and CNPase. Morphologic and immunohistochemical features confirmed a glial histogenesis for all tumors and allowed for their classification as diffuse, low- or high-grade astrocytoma; oligodendroglioma; or undefined glioma. Further research is needed to confirm or refute the hypothesis that canine GC represents an infiltrative growth pattern of canine glioma.

Monopolar Spindle 1 Kinase (MPS1/TTK) mRNA Expression is Associated with Earlier Development of Clinical Symptoms, Tumor Aggressiveness and Survival of Glioma Patients

Inhibition of the protein kinase MPS1, a mitotic spindle-checkpoint regulator, reinforces the effects of multiple therapies against glioblastoma multiforme (GBM) in experimental settings. We analyzed MPS1 mRNA-expression in gliomas WHO grade II, III and in clinical subgroups of GBM. Data were obtained by qPCR analysis of tumor and healthy brain specimens and correlated with the patients’ clinical data. MPS1 was overexpressed in all gliomas on an mRNA level (ANOVA, p < 0.01) and correlated with tumor aggressiveness. We explain previously published conflicting results on survival: high MPS1 was associated with poorer long term survival when all gliomas were analyzed combined in one group (Cox regression: t < 24 months, p = 0.009, Hazard ratio: 8.0, 95% CI: 1.7–38.4), with poorer survival solely in low-grade gliomas (LogRank: p = 0.02, Cox regression: p = 0.06, Hazard-Ratio: 8.0, 95% CI: 0.9–66.7), but not in GBM (LogRank: p > 0.05). This might be due to their lower tumor volume at the therapy start. GBM patients with high MPS1 mRNA-expression developed clinical symptoms at an earlier stage. This, however, did not benefit their overall survival, most likely due to the more aggressive tumor growth. Since MPS1 mRNA-expression in gliomas was enhanced with increasing tumor aggressiveness, patients with the worst outcome might benefit best from a treatment directed against MPS1.

Radiological Characteristics and Natural History of Adult IDH-Wildtype Astrocytomas with TERT Promoter Mutations

BACKGROUND

Adult IDH-wildtype astrocytomas with TERT promoter mutations (TERTp) are associated with a poor prognosis.

OBJECTIVE

To analyze the radiological presentation and natural history of adult IDH-wildtype astrocytomas with TERTp.

METHODS

We retrospectively reviewed the characteristics of 40 IDH-wildtype TERTp-mutant astrocytomas (grade II n = 19, grade III n = 21) and compared them to those of 114 IDH-mutant lower grade gliomas (LGG), of 92 IDH-wildtype TERTp-mutant glioblastomas, and of 15 IDH-wildtype TERTp-wildtype astrocytomas.

RESULTS

Most cases of IDH-wildtype TERTp-mutant astrocytomas occurred in patients aged >50 yr (88%) and presented as infiltrative lesions without contrast enhancement (73%) that were localized in the temporal and/or insular lobes (37.5%) or corresponded to a gliomatosis cerebri (43%). Thalamic involvement (33%) and extension to the brainstem (27%) were frequently observed, as was gyriform infiltration (33%). This radiological presentation was different from that of IDH-mutant LGG, IDH-wildtype TERTp-mutant glioblastomas, and IDH-wildtype TERTp-wildtype astrocytomas. Tumor evolution before treatment initiation was assessable in 17 cases. Ten cases demonstrated a rapid growth characterized by the apparition of a ring-like contrast enhancement and/or a median velocity of diametric expansion (VDE) ≥8 mm/yr but 7 cases displayed a slow growth (VDE <8 mm/yr) that could last several years before anaplastic transformation. Median overall survival of IDH-wildtype TERTp-mutant astrocytomas was 27 mo.

CONCLUSION

IDH-wildtype TERTp-mutant astrocytomas typically present as nonenhancing temporo-insular infiltrative lesions or as gliomatosis cerebri in patients aged >50 yr. In the absence of treatment, although rapid tumor growth is frequent, an initial falsely reassuring, slow growth can be observed.

Clinical relevance of molecular subgrouping of gliomatosis cerebri per 2016 WHO classification: a clinicopathological study of 89 cases

The extremely invasive phenotypes and genotypes related to progression of gliomatosis cerebri (GC) remain unclear although GC has been removed as an independent entity from the 2016 WHO classification. Hence, categorization of GC under the current WHO molecular classification is essential, and the molecular subgroups that might contribute to GC progression should be compared with the histopathological differences between initial and new lesions identified during follow-up. Analyses of IDH1/2 and TERTp mutations and 1p/19q co-deletion, and immunohistochemistry of IDH1-R132H, ATRX, p53 and galectin-3 were performed. Anaplastic astrocytoma, IDH-wildtype (AA-IDHwt) was the common molecular subgroup (52.8%), followed by diffuse astrocytoma, IDH-wildtype (DA-IDHwt) and AA, IDH-mutant (AA-IDHmt) (each 16.9%), DA-IDHmt (7.9%), glioblastoma (GBM)-IDHwt (3.3%) and GBM-IDHmt (2.2%). Approximately 92% of the AA-IDHwt lesions progressed to histologically confirmed GBM in the newly enhanced lesions harboring the TERTp mutation and expressing galectin-3. Similar to primary GBMs, GC-related GBMs that progressed from the IDHwt subgroups showed microvascular proliferation, palisading necrosis or thrombotic occlusion, implying that a subset of IDHwt subgroups may evolve to overt GBM. Molecular subgrouping did not provide the perfect prediction for the survival of GC patients. The AA-IDHwt group showed worse overall and progression-free survival (PFS) than the AA-IDHmt group. Biopsy plus radiotherapy, chemotherapy and temozolomide treatment for DA-IDHwt, and resection plus radiotherapy and temozolomide treatment for AA-IDHwt prolonged PFS. In conclusions, majority of GC was of the AA-IDHwt subgroup, which progressed to GBM. Molecular subgroups may assist in the selection of treatment modalities, because "GC pattern" still remains as a special growth of gliomas in WHO 2016 classification without established treatment guideline.

Gliomatosis Cerebri: A Unique Presentation with Accompanying Clinical Nuance

Gliomatosis cerebri (GC) has classically been considered a rare malignancy with a poor prognosis and is developmentally unique from solid tumors. More recently, GC has become better understood as a phenotype along the spectrum of gliomas and, most importantly, not mutually exclusive from the more common presentation of a tumor mass. The following case report illustrates not only the implications of the ontogeny of gliomas in clinical practice but also the successes that can accompany the early recognition of such a disease. Here, we report the presentation of a solid temporal lobe glioma, which, on presentation, was disseminating along well-defined mesolimbic white matter tracts. Once properly diagnosed and managed, the patient remarkably proceeded to achieve an impressive outcome given the extent of her pathology.

Treatment Strategies Based on Histological Targets against Invasive and Resistant Glioblastoma

Glioblastoma (GBM) is the most common and the most malignant primary brain tumor and is characterized by rapid proliferation, invasion into surrounding normal brain tissues, and consequent aberrant vascularization. In these characteristics of GBM, invasive properties are responsible for its recurrence after various therapies. The histomorphological patterns of glioma cell invasion have often been referred to as the “secondary structures of Scherer.” The “secondary structures of Scherer” can be classified mainly into four histological types as (i) perineuronal satellitosis, (ii) perivascular satellitosis, (iii) subpial spread, and (iv) invasion along the white matter tracts. In order to develop therapeutic interventions to mitigate glioma cell migration, it is important to understand the biological mechanism underlying the formation of these secondary structures. The main focus of this review is to examine new molecular pathways based on the histopathological evidence of GBM invasion as major prognostic factors for the high recurrence rate for GBMs. The histopathology-based pharmacological and biological targets for treatment strategies may improve the management of invasive and resistant GBMs.

Gliomatosis Cerebri Among Children and Adolescents: An Individual-Patient Data Meta-analysis of 182 Patients

BACKGROUND

Gliomatosis cerebri is a rare but fatal widespread infiltrating central nervous system tumor. We aimed to describe diagnostic and prognostic features of gliomatosis cerebri among children and adolescents.

METHODS

We conducted a systematic literature review for published case reports and case series on patients with histologically confirmed gliomatosis cerebri and extracted data on an individual patient level for those aged 0-18 years. Multivariable Cox proportional hazard models were fit for overall survival.

RESULTS

Following screening of 274 published studies, 182 gliomatosis cerebri patients (63% males) aged 0-18 years with individual-level data available were identified. The most common presenting symptoms were seizures (52%), focal motor deficits (36%), and headache (30%). Imaging showed bilateral hemisphere involvement in 60%, infratentorial infiltration in 39%, and a focal contrast-enhanced mass (type II gliomatosis cerebri) in 27% of cases. Anaplastic astrocytoma was the most common histologic subtype of pediatric gliomatosis cerebri, whereas MGMT promoter methylation, IDH1 mutations, and codeletion of 1p/19q were less common molecular aberrations, as compared to adult gliomatosis cerebri. In the multivariable analyses, age at diagnosis >4 years, extended central nervous system infiltration, coordination abnormalities, and cognitive decline were predictors of worse outcome. Conversely, IDH1 mutations were associated with prolonged overall survival. Chemotherapy and extended surgical resection were associated with improved outcome, whereas radiotherapy was not associated with overall survival and was inferior to chemotherapy alone.

CONCLUSION

Gliomatosis cerebri among children and adolescents presents distinct histopathologic and molecular features compared to adults. However, similar associations of chemotherapy, and, when feasible, extended surgical resection, with favorable outcomes were noted among the 2 age groups.

Integrated diagnostics of diffuse astrocytic and oligodendroglial tumors

BACKGROUND

Diffuse astrocytic and oligodendroglial gliomas are the most common neuroepithelial tumors. Their classification is based on the integration of histological and molecular findings according to the classification of tumors of the central nervous system published by the World Health Organization (WHO) in 2016.

OBJECTIVES

This review describes the different entities and variants of diffuse gliomas and summarizes the current diagnostic criteria for these tumors.

MATERIALS AND METHODS

Based on the 2016 WHO classification and selected other publications, the histomolecular diagnostics of diffuse gliomas is presented and illustrated.

RESULTS

Diffuse gliomas are divided into isocitrate dehydrogenase (IDH)-mutant or IDH-wildtype gliomas by detection of mutations in the IDH1 or IDH2 genes. Among the IDH-mutant gliomas, oligodendroglial tumors are characterized by combined losses of chromosome arms 1p and 19q. Loss of nuclear expression of the ATRX protein is a marker of IDH- mutant astrocytic gliomas. Glioblastoma, IDH-wildtype, is the most common diffuse glioma. Diffuse and anaplastic astrocytic gliomas without IDH mutation should be further evaluated for molecular features of glioblastoma, IDH-wildtype. Diffuse gliomas in the thalamus, brainstem, or spinal cord carrying a histone 3 (H3)-K27M mutation are classified as diffuse midline gliomas, H3-K27M-mutant. By determining the IDH and 1p/19q status, oligoastrocytomas can be stratified into either astrocytic or oligodendroglial gliomas. Gliomatosis cerebri is no longer regarded as a distinct glioma entity.

CONCLUSIONS

Diffuse gliomas can today be classified accurately and reproducibly by means of histological, immunohistochemical, and molecular analyses.

[Alterations in the WHO classification of brain tumors from 2016]

BACKGROUND

The World Health Organization (WHO) provides uniform definitions and a uniform nomenclature for tumors of various organs.

OBJECTIVE

What changes resulted from the 2016 WHO classification of tumors of the central nervous system?

MATERIAL AND METHODS

Changes in the definition and classification of brain tumors of the revised WHO classification are presented. Most changes evolve from the results of molecular pathology that were generated during the last decade.

RESULTS

For the first time the WHO classification of brain tumors is not based exclusively on histology. Molecular parameters add to the definition of a number of tumor entities. Especially the chapters of gliomas, medulloblastomas and other embryonal tumors have been restructured.

CONCLUSION

Advances in molecular pathology require a modular diagnostics scheme that integrates histological and molecular parameters into a final diagnosis. This approach will result in more precise tumor groups with respect to prognosis and therapy.

The landscape of postsurgical recurrence patterns in diffuse low-grade gliomas

Early and maximal safe surgical resection optionally followed by adjuvant treatment is currently recommended in diffuse low-grade glioma (DLGG). Although this management delays malignant transformation (MT), recurrence will most often occur. Because this relapse usually arises locally, reoperation can be considered, with possible further chemotherapy/radiotherapy. However, due to a prolonged overall survival, a large spectrum of unusual recurrence patterns begins to emerge during long-term follow-up, beyond the classical slow and local tumor re-growth. We review various atypical patterns of DLGG relapse, we discuss their pathophysiological mechanisms and how to adapt the treatment(s). Those patterns include very diffuse, ipsi- or bilateral gliomatosis-like progression, multicentric recurrence with emergence of remote low-grade or high-grade glioma, leptomeningeal dissemination, acute (early or delayed) local MT or bulky relapse into the operating cavity. This landscape of recurrence patterns may allow physicians to elaborate new tailored therapeutic strategies and scientists to develop original hypotheses for basic research.

Updates in the Neuoroimaging and WHO Classification of Primary CNS Gliomas: A Review of Current Terminology, Diagnosis, and Clinical Relevance From a Radiologic Prospective

As new advances in the genomics and imaging of CNS tumors continues to evolve, a standardized system for classification is increasingly essential to diagnosis and management. The molecular markers introduced in the 2016 WHO classification of CNS tumors bring both practical and conceptual advances to the characterization of gliomas, strengthening the prognostic and predictive value of terminology while shedding light on the underlying mechanisms that drive biologic behavior. The purpose of this article is to provide a succinct overview of primary intracranial gliomas from a neuroradiologic prospective and according to the 5th edition WHO classification that was revised in 2016. An update of the molecular markers pertinent to defining the major lineages of brain gliomas will be provided, followed by discussion of the terminology, grading and imaging features associated with individual entities. Neuroradiologists should be aware of the key genomic and radiomic features of common brain gliomas, and familiar with an integrated approach to their diagnosis and grading.

[Integrated diagnostics of diffuse astrocytic and oligodendroglial tumors. German version]

BACKGROUND

Diffuse astrocytic and oligodendroglial gliomas are the most common neuroepithelial tumors. Their classification is based on the integration of histological and molecular findings according to the classification of tumors of the central nervous system published by the World Health Organization (WHO) in 2016.

OBJECTIVES

This review describes the different entities and variants of diffuse gliomas and summarizes the current diagnostic criteria for these tumors.

MATERIALS AND METHODS

Based on the 2016 WHO classification and selected other publications, the histomolecular diagnostics of diffuse gliomas is presented and illustrated.

RESULTS

Diffuse gliomas are divided into isocitrate dehydrogenase (IDH)-mutant or IDH-wildtype gliomas by detection of mutations in the IDH1 or IDH2 genes. Among the IDH-mutant gliomas, oligodendroglial tumors are characterized by combined losses of chromosome arms 1p and 19q. Loss of nuclear expression of the ATRX protein is a marker of IDH- mutant astrocytic gliomas. Glioblastoma, IDH-wildtype, is the most common diffuse glioma. Diffuse and anaplastic astrocytic gliomas without IDH mutation should be further evaluated for molecular features of glioblastoma, IDH-wildtype. Diffuse gliomas in the thalamus, brainstem, or spinal cord carrying a histone 3 (H3)-K27M mutation are classified as diffuse midline gliomas, H3-K27M-mutant. By determining the IDH and 1p/19q status, oligoastrocytomas can be stratified into either astrocytic or oligodendroglial gliomas. Gliomatosis cerebri is no longer regarded as a distinct glioma entity.

CONCLUSIONS

Diffuse gliomas can today be classified accurately and reproducibly by means of histological, immunohistochemical, and molecular analyses.

WHO 2016 Classification of gliomas

Gliomas are the most frequent intrinsic tumours of the central nervous system and encompass two principle subgroups: diffuse gliomas and gliomas showing a more circumscribed growth pattern ('nondiffuse gliomas'). In the revised fourth edition of the WHO Classification of CNS tumours published in 2016, classification of especially diffuse gliomas has fundamentally changed: for the first time, a large subset of these tumours is now defined based on presence/absence of IDH mutation and 1p/19q codeletion. Following this approach, the diagnosis of (anaplastic) oligoastrocytoma can be expected to largely disappear. Furthermore, in the WHO 2016 Classification gliomatosis cerebri is not an entity anymore but is now considered as a growth pattern. The most important changes in the very diverse group of 'nondiffuse' gliomas and neuronal-glial tumours are the introduction of anaplastic pleomorphic xanthoastrocytoma, of diffuse leptomeningeal glioneuronal tumour and of RELA fusion-positive ependymoma as entities. In the last part of this review, after very briefly touching upon classification of neuronal, choroid plexus and pineal region tumours, some practical implications and challenges associated with the WHO 2016 Classification of gliomas are discussed.

Gliomatosis cerebri: a consensus summary report from the Second International Gliomatosis cerebri Group Meeting, June 22-23, 2017, Bethesda, USA

Gliomatosis cerebri (GC) is an aggressive glioma characterized by an invasive growth pattern and a dismal prognosis. The low incidence and non-specific symptoms at presentation pose unique challenges for early diagnosis and disease-specific research. There is no standard of care for the treatment of patients with a GC phenotype. Understanding the biology of this entity is a critical step in determining effective treatments. Toward this end, the Second International GC Group convened at National Institutes of Health, Bethesda on June 22nd-23rd 2017. This paper summarizes the main conclusions and recommendations for research priorities to fight this fatal condition.

Wide Range of Clinical Outcomes in Patients with Gliomatosis Cerebri Growth Pattern: A Clinical, Radiographic, and Histopathologic Study

BACKGROUND

The 2016 World Health Organization Classification of Central Nervous System Tumors categorizes gliomatosis cerebri growth pattern (GC) as a subgroup of diffuse infiltrating gliomas, defined by extent of brain involvement on magnetic resonance imaging (MRI). Clinical and radiographic features in GC patients are highly heterogeneous; however, prognosis has historically been considered poor.

SUBJECTS, MATERIALS, AND METHODS

We performed a retrospective search for patients at our institution meeting radiographic criteria of primary, type I GC (defined as diffuse tumor infiltration without associated tumor mass and contrast enhancement on MRI) and analyzed their clinical, imaging, and histopathologic features.

RESULTS

A total of 34 patients met radiographic criteria of primary, type I GC, and 33 had a confirmed histologic diagnosis of an infiltrating glial neoplasm. Age >47 years at diagnosis was associated with worse overall survival (OS) compared with age ≤47 years (hazard ratio [HR] 1.04, 95% confidence interval [CI] 1.01-1.07, p = .003). Patients with grade 2 tumors demonstrated a trend for improved OS compared with those with grade 3 tumors (HR 2.65, 95% CI 0.99-7.08, p = .051). Except for brainstem involvement, extent or location of radiographic involvement did not detectably affect clinical outcome. IDH mutation status identified a subgroup of GC patients with particularly long survival up to 25 years and was associated with longer time to progression (HR 4.81, 95% CI 0.99-23.47, p = .052).

CONCLUSION

Patients with primary, type I GC do not uniformly carry a poor prognosis, even in the presence of widespread radiographic involvement. Consistent with other reports, IDH mutation status may identify patients with improved clinical outcome. Molecular characterization, rather than MRI features, may be most valuable for prognostication and management of GC patients.

IMPLICATIONS FOR PRACTICE

Patients with gliomatosis cerebri growth pattern (GC) constitute a challenge to clinicians, given their wide range of clinical, histologic, and radiographic presentation, heterogeneous outcome patterns, and the lack of consensus on a standardized treatment approach. This study highlights that radiographic extent of disease-albeit category-defining-does not detectably influence survival and that IDH mutations may impact clinical outcome. Practicing oncologists should be aware that select GC patients may demonstrate exceptionally favorable survival times and prognosticate patients based on molecular markers, rather than imaging features alone.

2016 World Health Organization Classification of Central Nervous System Tumors

PURPOSE OF REVIEW

Since 1979, the World Health Organization (WHO) has periodically published a consensus classification and grading of tumors of the central nervous system (CNS) to ensure uniform histopathologic diagnostic criteria worldwide. In 2016, the WHO published an update of the fourth edition of the classification of CNS tumors. This article summarizes the major changes in the update and discusses their impact on clinical practice.

RECENT FINDINGS

For the first time, the 2016 revision of the WHO classification uses molecular parameters in addition to traditional histology to diagnose many CNS tumors, resulting in major restructuring of the classification of many tumors, especially gliomas, ependymomas, and medulloblastomas. Accordingly, nomenclature for selected entities now includes both a histopathologic diagnosis and defining molecular features.

SUMMARY

The use of integrated phenotypic and genotypic parameters for the classification of CNS tumors introduces greater objectivity to the diagnosis but also requires more widespread availability of molecular testing. It is hoped that these changes will lead to greater diagnostic accuracy with more biologically homogeneous diagnostic entities and improved patient management and determination of prognosis.

[IDH1- and IDH2-mutations in brain glial tumors - the new antioncogenic mechanism]

Mutant forms of the gene IDH1 progress significantly slower, have a lower risk of neoplastic transformation, and generally, mutations of this gene have a pronounced anti-oncogenic effect. At the same time, almost all mutations are quite stereotyped (98,9%) and occur in the same region of the gene - R132H mutations. IDH1 gene mutations is a complex multi-layered process, which is a completely new, not previously described anti-oncogene activation mechanism of intracellular protection. The reason that there is a mutation in the tumor cells is associated with de novo blocking differentiation processes and development of brain cells in the development process, as evidenced by severe cerebral hypoplasia in patients with congenital forms of this mutation. A completely new mechanism of antitumor protection has been described - stereotypical IDH1 gene mutation is a gene, in fact, is a key event, causing a cascade of further anti-oncogenic mechanisms in brain gliomas.

A clinical perspective on the 2016 WHO brain tumor classification and routine molecular diagnostics

The 2007 World Health Organization (WHO) classification of brain tumors did not use molecular abnormalities as diagnostic criteria. Studies have shown that genotyping allows a better prognostic classification of diffuse glioma with improved treatment selection. This has resulted in a major revision of the WHO classification, which is now for adult diffuse glioma centered around isocitrate dehydrogenase (IDH) and 1p/19q diagnostics. This revised classification is reviewed with a focus on adult brain tumors, and includes a recommendation of genes of which routine testing is clinically useful. Apart from assessment of IDH mutational status including sequencing of R132H-immunohistochemistry negative cases and testing for 1p/19q, several other markers can be considered for routine testing, including assessment of copy number alterations of chromosome 7 and 10 and of TERT promoter, BRAF, and H3F3A mutations. For "glioblastoma, IDH mutated" the term "astrocytoma grade IV" could be considered. It should be considered to treat IDH wild-type grades II and III diffuse glioma with polysomy of chromosome 7 and loss of 10q as glioblastoma. New developments must be more quickly translated into further revised diagnostic categories. Quality control and rapid integration of molecular findings into the final diagnosis and the communication of the final diagnosis to clinicians require systematic attention.

Magnetic resonance imaging features of canine gliomatosis cerebri

A retrospective, case series study was undertaken to identify magnetic resonance imaging (MRI) characteristics of gliomatosis cerebri in dogs. Fourteen dogs were included by review of histopathological records and contemporaneous MRI. On MRI, all lesions presented as ill-defined, intraaxial lesions within the left and right forebrain hemispheres with involvement of white and gray matter. Lesions presented as hyperintense areas on T2-weighted and FLAIR sequences and as hypointense or isointense areas on T1-weighted images, with mild parenchymal contrast enhancement in three dogs. Signal changes were noted in three to 10 cerebral lobes. Other most commonly affected structures were the thalamus (13), caudate nucleus (13), interthalamic adhesion (11), hypothalamus (11), callosal commissure (10), hippocampus (9), and quadrigeminal plate (8). Abnormalities within the caudal fossa were noted in 10 dogs. Solid tumor portions were identified in five dogs. The histopathological examination demonstrated in all dogs a widespread diffuse infiltration with neoplastic glial cells in white and gray matter with meningeal infiltration. Comparison between MRI and histopathology showed that all areas with signal changes on MRI corresponded to diffuse and dense infiltration with neoplastic cells. The signal intensity on T2-weighted and FLAIR images reflected the density of neoplastic cells. In all dogs, MRI underestimated lesion extent and meningeal infiltration. Involvement of the caudal fossa was not seen on MRI in three dogs. Despite this, MRI allowed identification of lesions extending into at least three cerebral lobes and therefore satisfying the criteria used for diagnosis of diffuse glioma with gliomatosis cerebri growth pattern in humans.

Incidence and survival of gliomatosis cerebri: a population-based cancer registration study

Gliomatosis cerebri (GC) comprises a rare widespread infiltrating growth pattern of diffuse gliomas. We explored the incidence patterns and survival rates of GC in a population-based registration sample from the Surveillance, Epidemiology and End, Results database (1973-2012). GC cases (n = 176) were identified based on their International Classification of Diseases in Oncology (ICD-O-3) morphology code (9381). We calculated age-adjusted incidence rates (AIR) and evaluated temporal trends. Survival was assessed with Kaplan-Meier curves and Cox regression models. The annual AIR of GC was 0.1/million. We noted increasing trends in the preceding registration years (1973-2002; annually, + 7%) and a tendency of clinical/radiological approaches to substitute the gold-standard histological assessment for diagnosis. GC was diagnosed in the entire age spectrum (range 1-98 years), but higher incidence rates (0.43/million) were noted among the elderly (≥ 65 years). A slight male preponderance was identified (male-to-female ratio: 1.4). Median overall survival was 9 months with a 5 year survival rate of 18%. Increasing age, primary tumor location not restricted to the cerebral hemispheres and rural residence at diagnosis were identified as negative prognostic factors, whereas receipt of radiotherapy, surgical treatment, race and method of diagnosis were not associated with outcome. This first comprehensive overview of GC epidemiology exemplifies the rarity of the disease, provides evidence for male preponderance and increased incidence among the elderly and shows lower survival rates compared to the published single center reports. Expansion of registration to histological and molecular characteristics would allow emergence of clinical prognostic factors at the population level.

A Pediatric Case of Diffuse Glioma Diagnosed at Autopsy

Sudden death from an undiagnosed primary intracranial neoplasm is extremely uncommon and even rarer in the pediatric population. Gliomatosis cerebri (GC) represents a growth pattern demonstrable by a variety of gliomas, predominating in adults. Herein we present a rare occurrence of diagnosis of a pediatric glioma with a GC pattern of infiltration at autopsy and compare the immunohistochemical results and molecular characteristics in this tumor to the small amount of published knowledge available about pediatric diffuse gliomas with widespread brain invasion.

Diffuse glioblastoma resembling acute hemorrhagic leukoencephalitis

We report the case of a young man with sudden onset of diplopia after an upper respiratory tract infection. Based on the first radiological findings acute hemorrhagic leukoencephalitis, a variant of acute disseminated encephalomyelitis, was suspected and treatment with high dose intravenous dexamethasone was started but it was stopped for intolerance. The patient clinically worsened, developing gait instability, ataxia and ophthalmoplegia; brain MRI performed 20 days later showed severe progression of the disease with subependymal dissemination. After brain biopsy of the right temporal lesion the histological diagnosis was glioblastoma. These findings suggest that MRI features of acute hemorrhagic leukoencephalitis may dissimulate the diagnosis of diffuse glioma/glioblastoma. This case underscores the importance of considering diffuse glioma in the differential diagnosis of atypical signs and symptoms of acute hemorrhagic leukoencephalitis and underlines the relevant role of integrating neuroradiologic findings with neuropathology.

Gliomatosis Cerebri: Current Understanding and Controversies

Gliomatosis cerebri (GC) is a rare, extensively infiltrating glioma involving multiple contiguous lobes of the brain. This lethal disease affects all age groups, and the majority of patients have a poor outcome despite aggressive treatment. Despite its initial recognition in 1938, GC remains a controversial entity with little consensus in its definition, histology, or treatment. The majority of GC tumors are astrocytic, although mixed phenotypes have been identified. Treatment of GC is challenging as surgery is generally not an option due to the extensive areas of brain involved, the benefit of radiation therapy is unclear, and no chemotherapy has proven efficacy. Due to the rarity of the disease and its heterogeneity, both at histopathological and molecular levels, it is difficult to conduct clinical trials tailored for this diagnosis. This review summarizes our current knowledge, examines clinical studies focusing on the treatment of GC, highlights ongoing challenges, and discusses the recent molecular insights into adult and pediatric GC. We conclude that, although no longer recognized as a distinct pathological entity, GC represents a unique disease phenotype. Given the histologic and molecular overlap with other diffuse gliomas, the research emphasis should be on investigating its unique invasive biology.

Practical implications of integrated glioma classification according to the World Health Organization classification of tumors of the central nervous system 2016

PURPOSE OF REVIEW

Morphological features identifiable by light microscopy have been the basis of brain tumor diagnostics for many decades. The revised WHO classification of tumors of the central nervous system 2016 combines histological and molecular features for an integrated classification. This new approach builds upon advances in brain tumor molecular genetics and has important practical implications.

RECENT FINDINGS

Molecular genetic studies revealed distinct glioma entities with specific genetic and epigenetic profiles. Evidence has been accumulated that molecular classification more reliably discriminates glioma entities and better predicts patient outcome than histological classification. Major glioma entities can be distinguished by four molecular biomarkers included in the new WHO classification, namely isocitrate dehydrogenase mutation, codeletion of chromosome arms 1p and 19q, codon 27 lysine-to-methionine mutation in H3 histones, and C11orf95-RELA gene fusions. Each is detectable by common techniques in routinely processed tissue specimens. Their integration into glioma classification greatly improves diagnostic accuracy but also has practical implications concerning establishment and quality control of novel techniques, increased costs and prolonged time to diagnosis.

SUMMARY

We summarize the relevant changes in the revised WHO classification of gliomas, outline the integrated approach, and discuss its practical implications and potential challenges.

European Association for Neuro-Oncology (EANO) guideline on the diagnosis and treatment of adult astrocytic and oligodendroglial gliomas

The European Association for Neuro-Oncology guideline provides recommendations for the clinical care of adult patients with astrocytic and oligodendroglial gliomas, including glioblastomas. The guideline is based on the 2016 WHO classification of tumours of the central nervous system and on scientific developments since the 2014 guideline. The recommendations focus on pathological and radiological diagnostics, and the main treatment modalities of surgery, radiotherapy, and pharmacotherapy. In this guideline we have also integrated the results from contemporary clinical trials that have changed clinical practice. The guideline aims to provide guidance for diagnostic and management decisions, while limiting unnecessary treatments and costs. The recommendations are a resource for professionals involved in the management of patients with glioma, for patients and caregivers, and for health-care providers in Europe. The implementation of this guideline requires multidisciplinary structures of care, and defined processes of diagnosis and treatment.

Prevalence and clinicopathological features of H3.3 G34-mutant high-grade gliomas: a retrospective study of 411 consecutive glioma cases in a single institution

A recurrent glycine-to-arginine/valine alteration at codon 34 (G34R/V) within H3F3A, a gene that encodes the replication-independent histone variant H3.3, reportedly occurs exclusively in pediatric glioblastomas. However, the clinicopathological and biological significances of this mutation have not been completely elucidated; especially, no such data exist for tumor samples from Japanese patients. We analyzed 411 consecutive glioma cases representing patients of all ages. Our results demonstrated that 14 patients (3.4%) harbored H3F3A mutations, of which four had G34R mutations and 10 had K27M mutations. G34R-mutant tumors were located in the parietal region in two patients and the basal ganglia in one patient. One patient showed multi-lobular extension similar to the pattern observed in gliomatosis cerebri. Regarding neuroradiological features, intratumoral calcification was evident in two cases and all cases showed no or scarce contrast enhancement on MRI. Histopathologically, the four G34R-mutant cases included three glioblastomas and one astroblastoma. We have also investigated alterations in histone methylation including H3K27me3, H3K9me3, and H3K4me3 in G34R-mutant samples by immunohistochemistry. These results indicate that G34R-mutant tumors are likely to show extensive infiltration and alterations in global histone trimethylation might also play an important role in G34R mutant tumors.

Bevacizumab for Patients with Recurrent Gliomas Presenting with a Gliomatosis Cerebri Growth Pattern

Bevacizumab has been shown to improve progression-free survival and neurologic function, but failed to improve overall survival in newly diagnosed glioblastoma and at first recurrence. Nonetheless, bevacizumab is widely used in patients with recurrent glioma. However, its use in patients with gliomas showing a gliomatosis cerebri growth pattern is contentious. Due to the marked diffuse and infiltrative growth with less angiogenic tumor growth, it may appear questionable whether bevacizumab can have a therapeutic effect in those patients. However, the development of nodular, necrotic, and/or contrast-enhancing lesions in patients with a gliomatosis cerebri growth pattern is not uncommon and may indicate focal neo-angiogenesis. Therefore, control of growth of these lesions as well as control of edema and reduction of steroid use may be regarded as rationales for the use of bevacizumab in these patients. In this retrospective patient series, we report on 17 patients with primary brain tumors displaying a gliomatosis cerebri growth pattern (including seven glioblastomas, two anaplastic astrocytomas, one anaplastic oligodendroglioma, and seven diffuse astrocytomas). Patients have been treated with bevacizumab alone or in combination with lomustine or irinotecan. Seventeen matched patients treated with bevacizumab for gliomas with a classical growth pattern served as a control cohort. Response rate, progression-free survival, and overall survival were similar in both groups. Based on these results, anti-angiogenic therapy with bevacizumab should also be considered in patients suffering from gliomas with a mainly infiltrative phenotype.