cIMPACT-NOW update 5: recommended grading criteria and terminologies for IDH-mutant astrocytomas

Surgical outcomes in high-grade adult type diffuse gliomas (ATDG) with a previous diagnosis of anaplastic astrocytoma without adjuvant therapy

INTRODUCTION

Gliomas pose a significant treatment challenge due to their varied genetic makeup and clinical presentations. This study examines a unique cohort of high-grade adult type diffuse gliomas (ATDG) previously diagnosed as anaplastic astrocytoma prior to the WHO 2021 tumor classification changes. This cohort chose to undergo only surgical resection without adjuvant therapies. We provide a rare dataset of patients allowing for new insight into the natural progression of this disease with surgical treatment alone.

METHODS

A retrospective review was conducted of patients who were operated on by a single surgeon from the years 2002-2022 and who were diagnosed as having a Grade III Anaplastic Astrocytoma before the WHO 2021 guidelines were published. Correcting for the criteria in the 2021 Guidelines resulted in a mixture of adult-type diffuse malignant gliomas (ATDG), including IDH-Mutant astrocytomas (Grade 3 and 4) and IDH-WT Glioblastoma. All patients included underwent surgical resection alone after declining any adjuvant therapy for various reasons.

RESULTS

A total of 20 patients met the inclusion criteria with an average age of 38 years. Among them, 15 had IDH-mutant (IDH-mt) Grade 3 astrocytomas (75 %), 1 had an IDH-mt Grade 4 astrocytoma (5 %), and 4 had IDH-wildtype (IDH-WT) glioblastomas (20 %). The 5-year survival rate for the entire cohort was 74.0 %. Grade 3 astrocytomas had a 5-year survival of 86.7 %, while Grade 4 astrocytomas and IDH-WT GBM patients exhibited a 5-year survival rate of 40 %. 5-year progression-free survival (PFS) rates were derived from the surgery date up until the recurrence or censorship. The collective cohort had a PFS rate of 34.3 %. Grade 3 astrocytomas achieved a 5-year PFS of 32.0 %, whereas Grade 4 astrocytomas and IDH-WT GBM reached a PFS of 40.0 %.

CONCLUSION

In our cohort study, we demonstrate that patients with ATDG can potentially achieve relative long-term survival through surgical resection alone. This unique cohort highlights the natural progression of this disease with surgery alone and provides the foundation for future more rigorous studies to evaluate the additive benefit of different adjuvant therapies. With evolving tumor classifications and variable responses to standard therapeutics, it becomes imperative to revisit and understand the additive benefits of different chemotherapeutic protocols in addition to surgical resection.

Dissecting PTPN7-driven aggressiveness in IDH-wildtype astrocytomas: multi-omics, clinical validation, and spatial transcriptomics for prognostic insights

BACKGROUND

Gliomas, particularly IDH-wildtype astrocytomas, remain highly aggressive and resistant to current therapies. Despite advances in molecular classification, effective therapeutic targets are still limited. Consequently, identifying new targets is essential to improve patient survival. PTPN7, a tyrosine phosphatase implicated in MAPK signaling, is known to play roles in various malignancies but remains underexplored in gliomas. This study examines the prognostic significance, spatial distribution, and immune-related functions of PTPN7, aiming to elucidate its potential as a prognostic role and therapeutic target in glioma treatment.

MATERIALS AND METHODS

We analyzed PTPN7 mRNA expression in gliomas via TCGA, CGGA, and single-cell RNA sequencing (GSE131928 and GSE89567). Kaplan determined prognostic significance-Meier and uni-/multi-variate Cox survival analyses. Gene set enrichment analysis (GSEA) was used to identify dysregulated pathways, immune signatures, and cell-type enrichments. We also applied CIBERSORT to evaluate the relationships between PTPN7 expression and 12-principal cell states and 22 immune populations. Spatial transcriptomics (Ivy Glioblastoma Atlas, 10 × Genomics Visium) mapped PTPN7 distribution; these findings were corroborated by immunohistochemistry-validated protein expression in 70 cases.

RESULTS

Pan-cancer analysis revealed PTPN7 overexpression in multiple malignancies, including glioma. Notably, PTPN7 was significantly elevated in IDH-wildtype astrocytomas, correlating with higher tumor grades and poorer overall survival. GSEA indicated that high PTPN7 is linked to T-cell differentiation, macrophage/monocyte activation, and dendritic cell-associated pathways. Both immune deconvolution and single-cell analyses showed that PTPN7 positively correlates with myeloid series and T-cell populations, supported by additional GSEA findings. In the Ivy dataset and spatial transcriptomics, PTPN7 was concentrated in peri-necrotic, cellular tumor, and slightly lower in the infiltrating border regions, consistent with immune interaction sites. Immunohistochemical data further demonstrated high PTPN7 expression tracks with increased tumor grade, reaching statistical significance in IDH-wildtype astrocytomas and confirming its clinical relevance.

CONCLUSION

This study positions PTPN7 as a prognostic biomarker and immune modulator in gliomas, particularly IDH-wildtype astrocytomas. Its expression correlates with tumor aggressiveness and immune infiltration, potentially driving glioma progression. Targeting PTPN7 may disrupt immune evasion and support tumor eradication, indicating a promising therapeutic avenue in immunotherapy-based strategies.

Anatomical heterogeneity in low-grade and high-grade gliomas: A multiscale perspective

BACKGROUND

Low-grade gliomas (LGGs) and high-grade gliomas (HGGs) often exhibit distinct spatial distributions, a phenomenon that remains incompletely understood. Based on previous research, we hypothesized that functional networks, neurotransmitters, and isocitrate dehydrogenase-1 (IDH-1) status characterize the spatial patterns of LGG and HGG.

METHODS

We analyzed 399 patients diagnosed with primary gliomas. First, we generated glioma frequency maps based on tumor grade, neurotransmitters, and IDH-1 status and constructed a brain functional connectivity network to explore heterogeneity in glioma location. Second, all tumor masks were mirror-symmetrized onto the brain's left hemisphere to facilitate feature extraction. We performed independent component analysis on merged four-dimensional files using Multivariate Exploratory Linear Optimized Decomposition into Independent Component (MELODIC), identifying four IDH-1 wild-type lesion covariance networks (IDHwt-LCNs) and three IDH-1 mutant lesion covariance networks (IDHmut-LCNs) with distinct spatial distributions, and analyzing correlation between the neurotransmitter levels and the IDH-wt/mut specific LCNs. Finally, we compared 42 white matter fibers extracted using XTRACT with 39 functional brain connectivity networks from the multi-subject dictionary learning (MSDL) atlas, revealing significant associations among the frontal aslant tract (FAT) and the intraparietal sulcus (IPS).

RESULTS

Our findings revealed high anatomical heterogeneity between LGG and HGG. Moreover, the high node strength played a critical role in the distinct spatial distribution of glioma. Significant correlations were observed between glioma frequency maps and dopaminergic, cholinergic, μ-opioid, and serotonergic neurotransmission. Furthermore, IDHwt/mut-LCNs analysis demonstrated that IDH-1 status influences glioma distribution, involving key brain structures. Lastly, we also found significant correlations between IDHwt/mut-LCNs and the neurotransmission of dopaminergic, cholinergic, μ-opioid, and serotonergic systems.

CONCLUSION

Our study highlighted the mechanisms by which functional networks, neurotransmitter systems, and IDH-1 status collectively contribute to the anatomical heterogeneity observed in LGG and HGG.

Canonical amplifications and CDKN2A/B loss refine IDH1/2-mutant astrocytoma prognosis

BACKGROUND

Molecular features have been incorporated alongside histologic criteria to improve glioma diagnostics and prognostication. CDKN2A/B homozygous-loss associates with worse survival in IDH1/2-mutant astrocytomas (IDHmut-astrocytomas), the presence of which denotes a grade 4 tumor independent of histologic features. However, no molecular features distinguish survival amongst histologically defined grade 2 and 3 IDHmut-astrocytomas.

METHODS

We assembled a cohort of patients ≥19 years old diagnosed with an IDHmut-astrocytoma between 1989 and 2020 from public datasets and several academic medical centers. Multivariate modeling and unbiased clustering were used to stratify risk.

RESULTS

We identified 998 IDHmut-astrocytoma patients (41.5% female; 85.6% white). Tumor grade, CDKN2A/B loss, and/or ≥1 focal amplification were associated with reduced survival. Grade 2/3 patients with intact CDKN2A/B and no focal amplifications survived the longest (OS 205.7 months). Survival for grade 2/3 cases with either CDKN2A/B hemizygous-loss or focal amplifications (80.4, 88.7 months respectively) did not differ significantly from grade 4 cases with intact CDKN2A/B and no amplifications (91.5 months, P = .93). Grade 4 patients with either hemizygous or homozygous loss of CDKN2A/B had the shortest survival (OS 31.9, 32.5 months respectively), followed by grade 4 cases with intact CDKN2A/B and focal gene amplifications (OS 55.9 months). Integrating CDKN2A/B status and amplifications alongside histopathologic grade refined overall survival prediction. Unbiased clustering revealed 9 distinct molecular profiles, with differential survival. IDHmut-astrocytomas with any CDKN2A/B loss clustered together, regardless of grade, and exhibited the poorest outcomes.

CONCLUSIONS

Combining CDKN2A/B hemizygous-loss and focal gene amplifications reveals a group of IDHmut-astrocytoma patients with an intermediate prognosis, refining IDHmut-astrocytoma classification.

Neuropathology Intraoperative Consultation

The goals of surgical neuropathology intra-operative consultation, (IOC), are to confirm sampling of diagnostic specimens and to guide surgical approaches. Understanding the clinical and imaging findings, and clear communication with the neurosurgeons, are critical for IOC to be informative. While neuropathologists typically lead this process at large academic institutions, other institutions may rely on surgical pathologists to provide neuropathology IOC. Thus, a stepwise approach for the evaluation of neuropathology specimens can be valuable. This review provides a diagnostic algorithm for neuropathology IOC and illustrates its utilization through nine example clinical vignettes. Pre-operative clinical and imaging findings, differential diagnosis, and critical diagnostic pitfalls are discussed. We discuss key findings that should be conveyed to the neurosurgery team at the time of IOC for optimal specimen handling and surgical guidance, to ensure adequate tissue sampling for subsequent pathologic and ancillary studies.

Comparison of Fluorescence In Situ Hybridization, Next-Generation Sequencing, and DNA Methylation Microarray for Copy Number Variation Assessment in Gliomas

Gene-level and chromosomal copy number variation (CNV) assessments are critical in the integrated diagnosis of gliomas. Whereas fluorescence in situ hybridization (FISH) has been traditionally employed for CNV detection, emerging technologies such as next-generation sequencing (NGS) and DNA methylation microarray (DMM) are available in clinical practice. Nevertheless, the comparative performance of these 3 assays and the concordance of them remain unclear. A retrospective cohort study comprising 104 patients diagnosed with gliomas was conducted at our hospital. We systematically compared FISH, NGS, and DMM for detecting the following 6 CNV-related diagnostic or prognostic parameters: epidermal growth factor receptor (EGFR), cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B), 1p, 19q, chromosome 7, and chromosome 10. All the 3 methods showed high consistency in EGFR assessment; however, FISH demonstrated relatively low concordance with NGS/DMM in detecting other parameters. In contrast, NGS and DMM exhibited strong concordance in the assessment of all the 6 parameters. Notably, discordant cases were associated with high-grade gliomas (grade 3/4; P < .05) and a high fraction of genome altered (P < .01), indicating high malignancy and genomic instability of discordant cases. This study elucidated the discrepancies and limitations of conventional FISH compared with NGS/DMM in CNV assessments. The discrepancies were associated with high-grade gliomas and genomic instability. We propose a process with recommendations on methods, highlighting the importance of integrated multiplatform assays in accurate clinical diagnosis.

SNUH methylation classifier for CNS tumors

BACKGROUND

Methylation profiling of central nervous system (CNS) tumors, pioneered by the German Cancer Research Center, has significantly improved diagnostic accuracy. This study aimed to further enhance the performance of methylation classifiers by leveraging publicly available data and innovative machine-learning techniques.

RESULTS

Seoul National University Hospital Methylation Classifier (SNUH-MC) addressed data imbalance using the Synthetic Minority Over-sampling Technique (SMOTE) algorithm and incorporated OpenMax within a Multi-Layer Perceptron to prevent labeling errors in low-confidence diagnoses. Compared to two published CNS tumor methylation classification models (DKFZ-MC: Deutsches Krebsforschungszentrum Methylation Classifier v11b4: RandomForest, 767-MC: Multi-Layer Perceptron), our SNUH-MC showed improved performance in F1-score. For 'Filtered Test Data Set 1,' the SNUH-MC achieved higher F1-micro (0.932) and F1-macro (0.919) scores compared to DKFZ-MC v11b4 (F1-micro: 0.907, F1-macro: 0.627). We evaluated the performance of three classifiers; SNUH-MC, DKFZ-MC v11b4, and DKFZ-MC v12.5, using specific criteria. We set established 'Decisions' categories based on histopathology, clinical information, and next-generation sequencing to assess the classification results. When applied to 193 unknown SNUH methylation data samples, SNUH-MC notably improved diagnosis compared to DKFZ-MC v11b4. Specifically, 17 cases were reclassified as 'Match' and 34 cases as 'Likely Match' when transitioning from DKFZ-MC v11b4 to SNUH-MC. Additionally, SNUH-MC demonstrated similar results to DKFZ-MC v12.5 for 23 cases that were unclassified by v11b4.

CONCLUSIONS

This study presents SNUH-MC, an innovative methylation-based classification tool that significantly advances the field of neuropathology and bioinformatics. Our classifier incorporates cutting-edge techniques such as the SMOTE and OpenMax resulting in improved diagnostic accuracy and robustness, particularly when dealing with unknown or noisy data.

The prognostic impact of CDKN2A/B hemizygous deletions in IDH-mutant glioma

BACKGROUND

Homozygous deletions of CDKN2A/B are known to predict poor prognosis in gliomas, but the impact of hemizygous deletions is less clear. This study aimed to evaluate the prognostic significance of hemizygous CDKN2A/B deletions in IDH-mutant low-grade astrocytomas and oligodendrogliomas.

METHODS

Tissue samples diagnosed as astrocytoma, IDH-mutant and oligodendroglioma, IDH-mutant, 1p/19q co-deleted CNS WHO grade 2 and 3 were collected from the archives of the Institute of Neuropathology in Heidelberg. DNA methylation analysis was performed on formalin-fixed paraffin-embedded samples. Evaluation of the CDKN2A/B locus was performed by visual inspection of copy-number plots derived from methylation-array data for each case. Hemizygous and homozygous losses were assessed in relation to whole chromosomal or larger segmental losses and gains in the chromosomal profile. Survival probabilities were assessed using the Kaplan-Meier method.

RESULTS

A total of 334 low-grade glioma cases were identified, including 173 astrocytomas and 161 oligodendrogliomas. Hemizygous deletions in CDKN2A/B (37/173 in astrocytomas, 15/161 in oligodendrogliomas) did not confer significantly worse survival outcomes compared to CDKN2A/B wild-type cases in neither low-grade astrocytoma (log-rank P = .2556; HR 2.29, 95% CI [0.76; 6.40], P = .135) nor oligodendroglioma (log-rank P = .2760; HR 0.17; 95% CI [0.01; 5.05]; P = .305), regardless of CNS WHO grade, which was further demonstrated on a subgroup of astrocytoma, IDH mutant CNS WHO 4 cases (log-rank P = .1680; HR 4.55, 95% CI [0.88; 24.51], P = .0689).

CONCLUSIONS

Hemizygous CDKN2A/B deletions do not significantly worsen OS or progression-free survival in IDH-mutant astrocytomas and oligodendrogliomas, CNS WHO grades 2 and 3.

Peptide‑based therapeutic strategies for glioma: Current state and prospects

Glioma is a prevalent form of primary malignant central nervous system tumor, characterized by its cellular invasiveness, rapid growth, and the presence of the blood-brain barrier (BBB)/blood-brain tumor barrier (BBTB). Current therapeutic approaches, such as chemotherapy and radiotherapy, have shown limited efficacy in achieving significant antitumor effects. Therefore, there is an urgent demand for new treatments. Therapeutic peptides represent an innovative class of pharmaceutical agents with lower immunogenicity and toxicity. They are easily modifiable via chemical means and possess deep tissue penetration capabilities which reduce side effects and drug resistance. These unique pharmacokinetic characteristics make peptides a rapidly growing class of new therapeutics that have demonstrated significant progress in glioma treatment. This review outlines the efforts and accomplishments in peptide-based therapeutic strategies for glioma. These therapeutic peptides can be classified into four types based on their anti-tumor function: tumor-homing peptides, inhibitor/antagonist peptides targeting cell surface receptors, interference peptides, and peptide vaccines. Furthermore, we briefly summarize the results from clinical trials of therapeutic peptides in glioma, which shows that peptide-based therapeutic strategies exhibit great potential as multifunctional players in glioma therapy.

Neuropathology practice in India: a survey of the current status of diagnostics and training in tertiary care centres

Neuropathology has been in existence as a speciality in India since the 1950s. Its practice has kept pace with the developments in the field, paralleling advancements in neurosurgery and neurosciences, especially in tertiary care centres. This nationwide survey, conducted across 52 centres, provides a comprehensive analysis of diagnostic infrastructure, training opportunities, and challenges in the practice of neuropathology. The results reveal variability in institutional setups, access to advanced diagnostic tools, and availability of training programs, reflecting a mixed landscape of progress and unmet needs. The majority of surveyed centres (78.8%) integrate neuropathology within general pathology, limiting its specialised focus. Only 17.3% recognise neuropathology as a distinct speciality, with only two functioning as independent departments. Training opportunities are gradually increasing. The Neuropathology Society of India has been instrumental in bridging some of the training gaps. Availability of in-house diagnostic facilities for workup of central nervous system (CNS) neoplastic lesions as per World Health Organization (WHO) CNS5 classification varies widely, with immunohistochemistry (IHC) being the most widely employed technique. Advanced molecular diagnostics, such as next-generation sequencing (NGS) are restricted to a few centres, while DNA methylation profiling is not available in-house in any of the surveyed centres. This limitation forces many institutions to outsource advanced testing, often at a significant financial burden to patients. Resource stratification reveals that 42.3% of surveyed centres are at resource level III, where surrogate IHC molecular markers are available and 32.7% are at resource level IV, with additional availability of basic molecular techniques such as fluorescence in situ hybridisation (FISH) and/or Sanger sequencing. Only 17.3% have advanced molecular techniques such as NGS and are at resource level V. Facilities to evaluate biopsies for diagnosis of non-neoplastic disorders such as neuromuscular diseases, infections, neurodegenerative and neurometabolic disorders are available in 82.3% of centres surveyed. Although muscle and nerve biopsies are performed in a large number of centres, in-house advanced molecular genetic diagnoses are limited to only three and electron microscopy to only seven centres. Comprehensive diagnostics for epilepsy, infections, and neurodegenerative diseases are concentrated in only a few of the tertiary care centres. Autopsies are being performed in 31 centres. Bio-banking and brain banking initiatives, although promising, remain largely confined to academic or research-driven projects. This survey thus highlights achievements in diagnostics and training, while emphasising the pressing need for a multifaceted approach for further improvement of neuropathology and thereby the quality of patient care in India. The survey reveals that although neuropathology services and training in India at tertiary care centres is better than at several other lower middle-income countries (LMICs), there is a need to increase infrastructure and training opportunities equitably. Strategic investment in molecular diagnostic facilities and digital pathology platforms, expanded training programs, and the recognition of neuropathology as a distinct speciality are critical for further improvement. Additionally, reducing financial burden on patients and expanding research infrastructure will be critical to advancing the field. Establishment of zonal nodal centres for referrals and collaboration between centres, both within India and globally, can further help address the disparities. Addressing all these issues will require concerted policy decisions at the governmental level along with the formulation of government supported programs and funding strategies.

Glioblastoma multiforme: insights into pathogenesis, key signaling pathways, and therapeutic strategies

Glioblastoma multiforme (GBM) is the most prevalent and aggressive primary brain tumor in adults, characterized by a poor prognosis and significant resistance to existing treatments. Despite progress in therapeutic strategies, the median overall survival remains approximately 15 months. A hallmark of GBM is its intricate molecular profile, driven by disruptions in multiple signaling pathways, including PI3K/AKT/mTOR, Wnt, NF-κB, and TGF-β, critical to tumor growth, invasion, and treatment resistance. This review examines the epidemiology, molecular mechanisms, and therapeutic prospects of targeting these pathways in GBM, highlighting recent insights into pathway interactions and discovering new therapeutic targets to improve patient outcomes.

Comparative Clinical-Imaging and Histogenetic Analysis Between Astrocytoma IDH-Mutant Grade 4 and Glioblastoma IDH-Wildtype-Is There Really a Worse One?

Background: Brain tumors pose a significant health threat, leading to high morbidity and mortality rates. Astrocytoma IDH-mutant grade 4 (A4IDHmt) and glioblastoma IDH-wildtype (G4IDHwt) exhibit similar clinical and imaging characteristics. This study aims to highlight the differences in their clinical evolution and histogenetic aspects with the possible therapeutic impact, as well as the adverse prognostic factors in patient survival. Methods: We performed a 10-year retrospective study of grade 4 gliomas, evaluating immunomarkers and FISH tests. We also quantified tumor necrosis and microvascular density. Results: A total of 81 cases were identified; 54.32% were A4IDHmt. We observed that A4IDHmt patients were younger (34.10% under 50) and had a higher survival rate (4.55%). This group also exhibited a more pronounced microvascular density (p = 0.010) and proliferative index (p = 0.026). G4IDHwt was associated with larger tumor volumes (94.84 cm3 vs. 86.14 cm3), lower resectability rates (82.88% vs. 87.67%), and a more significant immature cell population (83.78% vs. 68.18%). In the case of both, the negative risk on survival in the univariate analysis is given by advanced age (A4IDHmt: HR = 1.035, G4IDHwt: HR = 1.045) and p53 immunopositivity (A4IDHmt: HR = 6.962, G4IDHwt: HR = 4.680). Conclusions: The negative risk factors for A4IDHmt include the rapid onset of clinical symptoms (HR = 2.038), diabetes mellitus (HR = 2.311), arterial hypertension (HR = 2.325), residual tumor (HR = 2.662), increased residual tumor volume (HR = 1.060), increased microvascular density (HR = 1.096), and high tumor necrosis (HR = 1.097). For G4IDHwt, the negative risk factors consist of increased residual volume (HR = 1.023), lost PTEN immunoreaction (HR = 33.133), and unmethylated DNA status (HR = 6.765, respectively HR = 20.573). Even if it has more risk factors, A4IDHmt is the lesser evil.

Early progressive disease within 2 years in isocitrate dehydrogenase (IDH)-mutant astrocytoma may indicate radiation necrosis

BACKGROUND

Isocitrate dehydrogenase-mutant astrocytoma without cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) homozygous deletion typically follows a slow clinical course. However, some cases show early progression on magnetic resonance imaging, and these characteristics remain under-reported. This study aimed to elucidate the characteristics of isocitrate dehydrogenase-mutant astrocytoma showing early progression on magnetic resonance imaging.

METHODS

This retrospective study included 52 cases of primary astrocytoma, isocitrate dehydrogenase-mutant, Central Nervous System (CNS) 5 World Health Organization grade 2-3 according to the World Health Organization 2021 classification. Patients underwent surgery followed by radiation therapy and/or chemotherapy at our institution from 2006 to 2019. Progression-free survival and overall survival were analyzed.

RESULTS

There were 24 and 28 grade 2 and grade 3 astrocytomas, respectively. The median patient age was 38 years. Forty-three patients underwent radiotherapy. Progression was diagnosed by magnetic resonance imaging in 22 patients with initial radiotherapy. Thirteen of the 22 patients underwent surgery, and seven of the 13 patients received surgery within 24 months of the initial radiotherapy. Histopathologically, radiation necrosis was confirmed in four of these seven patients (57.1%). The true progression-free survival rate, excluding radiation necrosis, at 2 years after surgery was 91.3% for grade 2 astrocytoma and 88.5% for grade 3 astrocytoma. The 5-year overall survival rate was 85.7% for grade 2 tumours and 76.4% for grade 3 tumours.

CONCLUSIONS

Radiation necrosis should be considered in cases showing early progression of isocitrate dehydrogenase-mutant astrocytoma, and a second surgery should be performed to confirm true recurrence or radiation necrosis. Astrocytomas with telomerase reverse-transcriptase promoter mutations may relapse relatively early and should be followed up with caution.

Unraveling the heterogeneity of WHO grade 4 gliomas: insights from clinical, imaging, and molecular characterization

PURPOSE

The 2021 WHO classification of central nervous system tumors introduced molecular criteria to stratify Grade 4 gliomas, which remain heterogeneous. This study aims to elucidate the clinical, radiological, and molecular characteristics of WHO Grade 4 gliomas, focusing on their prognostic implications and the development of a predictive model for astrocytoma IDH-mutant WHO Grade 4 (A4).

METHODS

A retrospective cohort of 223 patients from Beijing Tiantan Hospital was analyzed. Clinical, radiological, and histopathological data were combined with molecular profiling, focusing on IDH mutations, TERT promoter mutations, and MGMT methylation. A predictive model was developed using LASSO regression to distinguish A4 from glioblastomas and validated with an external dataset from UCSF.

RESULTS

The cohort included 201 glioblastomas (90.1%) and 22 A4 cases (9.9%). A4 tumors were associated with younger age, higher MGMT promoter methylation, lower rates of TERT mutations, and distinct radiological features, such as cortical non-enhancing tumor infiltration (CnCE). Patients with A4 demonstrated significantly better survival outcomes compared to glioblastoma patients (p < 0.001). The predictive model for A4, incorporating age, tumor margin, and CnCE, achieved an AUC of 0.890 in the training set and 0.951 in the validation set.

CONCLUSION

Integrating molecular and clinical criteria improves prognostication in Grade 4 gliomas. The predictive model developed in this study effectively identifies A4 tumors, facilitating more personalized therapeutic strategies.

IDH-mutant astrocytomas with primitive neuronal component have a distinct methylation profile and a higher risk of leptomeningeal spread

IDH-mutant astrocytomas are diffuse gliomas that are defined by characteristic mutations in IDH1 or IDH2 and do not have complete 1p/19q co-deletion. The established grading criteria include histological features of brisk mitotic activity (grade 3) and necrosis and/or microvascular proliferation (grade 4). In addition, homozygous deletion of the CDKN2A/B locus has recently been implemented as a molecular marker for grade 4 IDH-mutant astrocytomas. Here, we describe a subgroup of high-grade IDH-mutant astrocytomas characterised by a primitive neuronal component based on histology and a distinct DNA methylation profile (n = 51, ASTRO PNC). Misinterpretation as carcinoma metastasis was common, since GFAP expression was absent in the primitive neuronal component, whereas TTF-1 expression was detected in 15/19 cases (79%) based on immunohistochemistry. Apart from mutations in IDH1, TP53, and ATRX, we observed enrichment for alterations in RB1 (n = 19/51, 37%) and MYCN (n = 14/51, 27%). Homozygous CDKN2A/B deletion (n = 1/51, 2%) and CDK4 amplification (n = 3/51, 6%) were relatively rare events. Clinical (n = 31 patients) and survival data (n = 23 patients) indicate a clinical behaviour similar to other CNS WHO grade 4 IDH-mutant astrocytomas, however with an increased risk for leptomeningeal (n = 7) and extra-axial (n = 2) spread. Taken together, ASTRO PNC is defined by a distinct molecular and histological appearance that can mimic metastatic disease and typically follows an aggressive clinical course.

Spatially resolved transcriptomics and graph-based deep learning improve accuracy of routine CNS tumor diagnostics

The diagnostic landscape of brain tumors integrates comprehensive molecular markers alongside traditional histopathological evaluation. DNA methylation and next-generation sequencing (NGS) have become a cornerstone in central nervous system (CNS) tumor classification. A limiting requirement for NGS and methylation profiling is sufficient DNA quality and quantity, which restrict its feasibility. Here we demonstrate NePSTA (neuropathology spatial transcriptomic analysis) for comprehensive morphological and molecular neuropathological diagnostics from single 5-µm tissue sections. NePSTA uses spatial transcriptomics with graph neural networks for automated histological and molecular evaluations. Trained and evaluated across 130 participants with CNS malignancies and healthy donors across four medical centers, NePSTA predicts tissue histology and methylation-based subclasses with high accuracy. We demonstrate the ability to reconstruct immunohistochemistry and genotype profiling on tissue with minimal requirements, inadequate for conventional molecular diagnostics, demonstrating the potential to enhance tumor subtype identification with implications for fast and precise diagnostic workup.

High p16INK4A expression in glioblastoma is associated with senescence phenotype and better prognosis

Glioblastoma, isocitrate dehydrogenase (IDH)-wildtype (GBM), is the most malignant brain tumor in adults, with limited therapeutic intervention. Previous studies have identified a few prognostic markers for GBM, including the methylation status of O6-methylguanine-DNA methyltransferase (MGMT) promoter, TERT promoter mutation, EGFR amplification, and CDKN2A/2B deletion. However, the classification of GBM remains incomplete, necessitating a comprehensive analysis. In this study, we investigated the impact of p16INK4A expression in GBM and found that p16INK4A-high GBM exhibits distinct characteristics compared to p16INK4A-low GBM. Specifically, tumor cells with p16INK4A-high expression display a senescent phenotype and are correlated with higher intra-tumoral immune cell infiltration. Furthermore, an association was observed between elevated p16INK4A expression in GBM and extended overall survival of patients. Our in vivo and in vitro studies revealed that CCL13 is predominantly expressed by p16INK4A-high GBM cells. The released CCL13 enhances the infiltration of T cells within the tumor, potentially contributing to the improved prognosis observed in patients with high p16INK4A expression. These findings suggest that tumor cells with a senescence phenotype in GBM, through the secretion of chemokines such as CCL13, may augment immune cell infiltration and potentially enhance patient outcomes by creating a more immunologically active tumor microenvironment.

Nanopore-based random genomic sampling for intraoperative molecular diagnosis

BACKGROUND

Central nervous system tumors are among the most lethal types of cancer. A critical factor for tailored neurosurgical resection strategies depends on specific tumor types. However, it is uncommon to have a preoperative tumor diagnosis, and intraoperative morphology-based diagnosis remains challenging. Despite recent advances in intraoperative methylation classifications of brain tumors, accuracy may be compromised by low tumor purity. Copy number variations (CNVs), which are almost ubiquitous in cancer, offer highly sensitive molecular biomarkers for diagnosis. These quantitative genomic alterations provide insight into dysregulated oncogenic pathways and can reveal potential targets for molecular therapies.

METHODS

We develop iSCORED, a one-step random genomic DNA reconstruction method that enables efficient, unbiased quantification of genome-wide CNVs. By concatenating multiple genomic fragments into long reads, the method leverages low-pass sequencing to generate approximately 1-2 million genomic fragments within 1 h. This approach allows for ultrafast high-resolution CNV analysis at a genomic resolution of 50 kb. In addition, concurrent methylation profiling enables brain tumor methylation classification and identifies promoter methylation in amplified oncogenes, providing an integrated diagnostic approach.

RESULTS

In our retrospective cohort of 26 malignant brain tumors, iSCORED demonstrated 100% concordance in CNV detection, including chromosomal alterations and oncogene amplifications, when compared to clinically validated assays such as Next-Generation Sequencing and Chromosomal Microarray. Furthermore, we validated iSCORED's real-time applicability in 15 diagnostically challenging primary brain tumors, achieving 100% concordance in detecting aberrant CNV detection, including diagnostic chromosomal gains/losses and oncogene amplifications (10/10). Of these, 14 out of 15 brain tumor methylation classifications aligned with final pathological diagnoses. This streamlined workflow-from tissue arrival to automatic generation of CNV and methylation reports-can be completed within 105 min.

CONCLUSIONS

The iSCORED pipeline represents the first method capable of high-resolution CNV detection within the intraoperative timeframe. By combining CNV detection and methylation classification, iSCORED provides a rapid and comprehensive molecular diagnostic tool that can inform rapid clinical decision. The integrated approach not only enhances the accuracy of tumor diagnosis but also optimizes surgical planning and identifies potential molecular therapies, all within the critical intraoperative timeframe.

IDH-mutant glioma risk stratification via whole slide images: Identifying pathological feature associations

This article aims to develop and validate a pathological prognostic model for predicting prognosis in patients with isocitrate dehydrogenase (IDH)-mutant gliomas and reveal the biological underpinning of the prognostic pathological features. The pathomic model was constructed based on whole slide images (WSIs) from a training set (N = 486) and evaluated on internal validation set (N = 209), HPPH validation set (N = 54), and TCGA validation set (N = 352). Biological implications of PathScore and individual pathomic features were identified by pathogenomics set (N = 100). The WSI-based pathological signature was an independent prognostic factor. Incorporating the pathological features into a clinical model resulted in a pathological-clinical model that predicted survival better than either the pathological model or clinical model alone. Ten categories of pathways (metabolism, proliferation, immunity, DNA damage response, disease, migrate, protein modification, synapse, transcription and translation, and complex cellular functions) were significantly correlated with the WSI-based pathological features.

Contemporary prognostic signatures and refined risk stratification of gliomas: An analysis of 4400 tumors

BACKGROUND

With the significant shift in the classification, risk stratification, and standards of care for gliomas, we sought to understand how the overall survival of patients with these tumors is impacted by molecular features, clinical metrics, and treatment received.

METHODS

We assembled a cohort of patients with histopathologically diagnosed glioma from The Cancer Genome Atlas (TCGA), Project Genomics Evidence Neoplasia Information Exchange, and Dana-Farber Cancer Institute/Brigham and Women's Hospital. This incorporated retrospective clinical, histological, and molecular data alongside a prospective assessment of patient survival.

RESULTS

Of 4400 gliomas were identified: 2195 glioblastomas, 1198 IDH1/2-mutant astrocytomas, 531 oligodendrogliomas, 271 other IDH1/2-wild-type gliomas, and 205 pediatric-type glioma. Molecular classification updated 27.2% of gliomas from their original histopathologic diagnosis. Examining the distribution of molecular alterations across glioma subtypes revealed mutually exclusive alterations within tumorigenic pathways. Non-TCGA patients had significantly improved overall survival compared to TCGA patients, with 26.7%, 55.6%, and 127.8% longer survival for glioblastoma, IDH1/2-mutant astrocytoma, and oligodendroglioma, respectively (all P < .01). Several prognostic features were characterized, including NF1 alteration and 21q loss in glioblastoma, and EGFR amplification and 22q loss in IDH1/2-mutant astrocytoma. Leveraging the size of this cohort, nomograms were generated to assess the probability of overall survival based on patient age, the molecular features of a tumor, and the treatment received.

CONCLUSIONS

By applying modern molecular criteria, we characterize the genomic diversity across glioma subtypes, identify clinically applicable prognostic features, and provide a contemporary update on patient survival to serve as a reference for ongoing investigations.

IDH-mutant gliomas in children and adolescents - from biology to clinical trials

Gliomas account for nearly 30% of all primary central nervous system (CNS) tumors in children and adolescents and young adults (AYA), contributing to significant morbidity and mortality. The updated molecular classification of gliomas defines molecularly diverse subtypes with a spectrum of tumors associated with age-distinct incidence. In adults, gliomas are characterized by the presence or absence of mutations in isocitrate dehydrogenase (IDH), with mutated IDH (mIDH) gliomas providing favorable outcomes and avenues for targeted therapy with the emergence of mIDH inhibitors. Despite their rarity, IDH mutations have been reported in 5-15% of pediatric glioma cases. Those with primary mismatch-repair deficient mIDH astrocytomas (PMMRDIA) have a particularly poor prognosis. Here, we describe the biology of mIDH gliomas and review the literature regarding the emergence of mIDH inhibitors, including clinical trials in adults. Given the paucity of clinical trial data from pediatric patients with mIDH glioma, we propose guidelines for the inclusion of pediatric and AYA patients with gliomas onto prospective trials and expanded access programs as well as the potential of combined mIDH inhibition and immunotherapy in the treatment of patients with PMMRDIA at high risk of progression.

Recent Advancements and Future Perspectives on Molecular Biomarkers in Adult Lower-Grade Gliomas

ABSTRACT

There has been a significant paradigm shift in the clinical management of lower-grade glioma patients given the recent updates to the 2021 World Health Organization classification along with long-term results from randomized phase III clinical trials. As a result, we are now better able to diagnose and assign patients to the most appropriate treatment course. This review provides a comprehensive summary of the most robust and reliable molecular biomarkers for adult lower-grade gliomas and discusses current challenges facing this patient population that future correlative biology studies combined with advancements in technologies could help overcome.

cIMPACT-NOW update 9: Recommendations on utilization of genome-wide DNA methylation profiling for central nervous system tumor diagnostics

Genome-wide DNA methylation signatures correlate with and distinguish central nervous system (CNS) tumor types. Since the publication of the initial CNS tumor DNA methylation classifier in 2018, this platform has been increasingly used as a diagnostic tool for CNS tumors, with multiple studies showing the value and utility of DNA methylation-based classification of CNS tumors. A Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy (cIMPACT-NOW) Working Group was therefore convened to describe the current state of the field and to provide advice based on lessons learned to date. Here, we provide recommendations for the use of DNA methylation-based classification in CNS tumor diagnostics, emphasizing the attributes and limitations of the modality. We emphasize that the methylation classifier is one diagnostic tool to be used alongside previously established diagnostic tools in a fully integrated fashion. In addition, we provide examples of the inclusion of DNA methylation data within the layered diagnostic reporting format endorsed by the World Health Organization (WHO) and the International Collaboration on Cancer Reporting. We emphasize the need for backward compatibility of future platforms to enable accumulated data to be compatible with new versions of the array. Finally, we outline the specific connections between methylation classes and CNS WHO tumor types to aid in the interpretation of classifier results. It is hoped that this update will assist the neuro-oncology community in the interpretation of DNA methylation classifier results to facilitate the accurate diagnosis of CNS tumors and thereby help guide patient management.

Clinical research framework proposal for ketogenic metabolic therapy in glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor in adults, with a universally lethal prognosis despite maximal standard therapies. Here, we present a consensus treatment protocol based on the metabolic requirements of GBM cells for the two major fermentable fuels: glucose and glutamine. Glucose is a source of carbon and ATP synthesis for tumor growth through glycolysis, while glutamine provides nitrogen, carbon, and ATP synthesis through glutaminolysis. As no tumor can grow without anabolic substrates or energy, the simultaneous targeting of glycolysis and glutaminolysis is expected to reduce the proliferation of most if not all GBM cells. Ketogenic metabolic therapy (KMT) leverages diet-drug combinations that inhibit glycolysis, glutaminolysis, and growth signaling while shifting energy metabolism to therapeutic ketosis. The glucose-ketone index (GKI) is a standardized biomarker for assessing biological compliance, ideally via real-time monitoring. KMT aims to increase substrate competition and normalize the tumor microenvironment through GKI-adjusted ketogenic diets, calorie restriction, and fasting, while also targeting glycolytic and glutaminolytic flux using specific metabolic inhibitors. Non-fermentable fuels, such as ketone bodies, fatty acids, or lactate, are comparatively less efficient in supporting the long-term bioenergetic and biosynthetic demands of cancer cell proliferation. The proposed strategy may be implemented as a synergistic metabolic priming baseline in GBM as well as other tumors driven by glycolysis and glutaminolysis, regardless of their residual mitochondrial function. Suggested best practices are provided to guide future KMT research in metabolic oncology, offering a shared, evidence-driven framework for observational and interventional studies.

Homozygous CDKN2A/B deletions in low- and high-grade glioma: a meta-analysis of individual patient data and predictive values of p16 immunohistochemistry testing

CDKN2A/B deletions are prognostically relevant in low- and high-grade gliomas. Data on this is derived from heterogeneous series, an accurate estimation of survival risk from homozygous CDKN2A/B deletion is missing. Besides genetic testing, p16-immunohistochemistry (IHC) as a less cost intensive means for indirect detection of CDKN2A/B alterations is possible but not validated in larger datasets. The present meta-analysis aimed to (1) reconstruct individual patient data (IPD) and estimate overall survival (OS) stratified by CDKN2A/B status from all literature and to (2) determine accuracy of p16 testing for CDKNA2/B detection from published studies. For survival analysis according to CDKN2A/B status 460 records were screened, four articles with 714 participants were included. In IDH-wildtype (IDH-wt) gliomas, 57.07% harbored the deletion compared to 9.76% in IDH-mutant (IDH-mut) gliomas. Median OS of patients with IDH-wt gliomas and homozygous CDKN2A/B deletion was 13.0 months compared to 18.0 months with non-deleted CDKN2A/B (p = 0.014, Log-Rank). With homozygous deletion of CDKN2A/B the risk of death was increased by 1.5 (95%-CI 1.1-2.1). Median OS in patients with IDH-mut gliomas without CDKN2A/B deletion was 92.0 months compared to 40.0 months with CDKN2A/B deletion (p < 0.001, Log-Rank). CDKN2A/B deletions were associated with a significantly shorter OS (HR = 3.2; 95%-CI 2.2-5.5). For p16 IHC analysis, 10 eligible studies with 1087 examined samples were included. The cut-off for retention differed between the studies. In 588/662 p16 retained cases CDKN2A/B deletions was not detected, implying a negative predictive value (NPV) of p16 staining of 88.8%. Conversely, 279/425 p16 absent cases showed a CDKN2A/B deletion resulting in a positive predictive value (PPV) of 65.6%. Sensitivity of p16 staining for CDKN2A/B detection was 79.0%, specificity 80.1%. Highest diagnostic accuracy of p16 IHC was reached with a cut-off of > 5% and within IDH-mut glioma.

All-in-one bimodal DNA and RNA next-generation sequencing panel for integrative diagnosis of glioma

Previously, we constructed a DNA-based next-generation sequencing (NGS) panel for an integrated diagnosis of gliomas according to the 2021 World Health Organization classification system. The aim of the current study was to evaluate the feasibility of a modified panel to include fusion gene detection via RNA-based analysis. Using this bimodal DNA/RNA panel, we analyzed 210 cases of gliomas and others to identify fusion genes in addition to gene alterations, including TERT promoter (TERTp) mutation and 1p/19q co-deletion, in formalin-fixed paraffin-embedded tissues. Of the 210 patients, fusion genes were detected in tumors of 35 patients. Eighteen of 112 glioblastomas (GBs) harbored fusion genes, including EGFR and FGFR3 fusions. In IDH-mutant astrocytoma, 6 of 30 cases showed fusion genes such as MET and NTRK2 fusions. Eleven molecular GBs and 20 not-elsewhere-classified cases harbored no gene fusions. Other 11 tumors including ependymoma, pilocytic astrocytoma, diffuse hemispheric glioma, infant-type hemispheric glioma, and solitary fibrous tumors exhibited diagnostic fusion genes. Overall, our results suggest that the all-in-one bimodal DNA/RNA panel is reliable for detecting diagnostic gene alterations in accordance with the latest WHO classification. The integrative pathological and molecular strategy could be valuable in confirmation of diagnosis and selection of treatment options for brain tumors.

Molecular Testing in Gliomas: What is Necessary in Routine Clinical Practice?

PURPOSE OF REVIEW

A number of molecular characteristics are essential for accurate diagnosis and prognostication in glioma.

RECENT FINDINGS

The 2021 WHO classification of brain tumors and recent Food and Drug Administration (FDA) pathology agnostic drug approvals highlight the importance of molecular testing in the management of glioma. For diffuse gliomas, it is important to identify IDH mutations, given the favorable clinical behavior and potential for using FDA approved IDH inhibitors in the near future. MGMT promoter methylation testing is the most established molecular marker for response to temozolomide in IDH wild-type glioblastoma and in turn impacts overall survival. Moreover, identification of certain mutations and molecular markers, such as BRAF V600E, hypermutation or elevated tumor-mutational burden and NTRK fusions allow for the use of FDA approved agents that are tumor-agnostic. Finally, molecular testing opens options for clinical trials that are essential for diseases with limited treatment options like gliomas.

A clinically feasible algorithm for the parallel detection of glioma-associated copy number variation markers based on shallow whole genome sequencing

Molecular features are incorporated into the integrated diagnostic system for adult diffuse gliomas. Of these, copy number variation (CNV) markers, including both arm-level (1p/19q codeletion, +7/-10 signature) and gene-level (EGFR gene amplification, CDKN2A/B homozygous deletion) changes, have revolutionized the diagnostic paradigm by updating the subtyping and grading schemes. Shallow whole genome sequencing (sWGS) has been widely used for CNV detection due to its cost-effectiveness and versatility. However, the parallel detection of glioma-associated CNV markers using sWGS has not been optimized in a clinical setting. Herein, we established a model-based approach to classify the CNV status of glioma-associated diagnostic markers with a single test. To enhance its clinical utility, we carried out hypothesis testing model-based analysis through the estimation of copy ratio fluctuation level, which was implemented individually and independently and, thus, avoided the necessity for normal controls. Besides, the customization of required minimal tumor fraction (TF) was evaluated and recommended for each glioma-associated marker to ensure robust classification. As a result, with 1× sequencing depth and 0.05 TF, arm-level CNVs could be reliably detected with at least 99.5% sensitivity and specificity. For EGFR gene amplification and CDKN2A/B homozygous deletion, the corresponding TF limits were 0.15 and 0.45 to ensure the evaluation metrics were both higher than 97%. Furthermore, we applied the algorithm to an independent glioma cohort and observed the expected sample distribution and prognostic stratification patterns. In conclusion, we provide a clinically applicable algorithm to classify the CNV status of glioma-associated markers in parallel.

Evolution of Molecular Biomarkers and Precision Molecular Therapeutic Strategies in Glioblastoma

Glioblastoma is the most commonly occurring malignant brain tumor, with a high mortality rate despite current treatments. Its classification has evolved over the years to include not only histopathological features but also molecular findings. Given the heterogeneity of glioblastoma, molecular biomarkers for diagnosis have become essential for initiating treatment with current therapies, while new technologies for detecting specific variations using computational tools are being rapidly developed. Advances in molecular genetics have made possible the creation of tailored therapies based on specific molecular targets, with various degrees of success. This review provides an overview of the latest advances in the fields of histopathology and radiogenomics and the use of molecular markers for management of glioblastoma, as well as the development of new therapies targeting the most common molecular markers. Furthermore, we offer a summary of the results of recent preclinical and clinical trials to recognize the current trends of investigation and understand the possible future directions of molecular targeted therapies in glioblastoma.

High-Grade Thalamic Glioma: Case Report with Literature Review

This case report delves into the case of a 56-year-old female patient presenting with progressive cephalalgia syndrome, nausea, vomiting, and gait disorders, diagnosed with a high-grade thalamic glioma. Glioma is the most common form of central nervous system (CNS) neoplasm that originates from glial cells. Gliomas are diffusely infiltrative tumors that affect the surrounding brain tissue. Glioblastoma is the most malignant type, while pilocytic astrocytomas are the least malignant brain tumors. In the past, these diffuse gliomas were classified into different subtypes and grades based on histopathologies such as a diffuse astrocytoma, oligodendrogliomas, or mixed gliomas/oligoastrocytomas. Currently, gliomas are classified based on molecular and genetic markers. After the gross total resection, a postoperative brain CT scan was conducted, which confirmed the quasi-complete resection of the tumor. The successful gross total resection of the tumor in this case, coupled with significant neurological improvement postoperatively, illustrates the potential benefits of aggressive surgical management for thalamic gliomas. This report advocates for further research to assess the efficacy of such interventions in malignant cases and to establish standardized treatment protocols, considering the heterogeneity in prognostic outcomes and the advancements in molecular diagnostics that offer deeper insights into glioma oncogenesis and progression.

Epigenetic landscape reorganisation and reactivation of embryonic development genes are associated with malignancy in IDH-mutant astrocytoma

Accurate grading of IDH-mutant gliomas defines patient prognosis and guides the treatment path. Histological grading is challenging, and aside from CDKN2A/B homozygous deletions in IDH-mutant astrocytomas, there are no other objective molecular markers used for grading. RNA-sequencing was conducted on primary IDH-mutant astrocytomas (n = 138) included in the prospective CATNON trial, which was performed to assess the prognostic effect of adjuvant and concurrent temozolomide. We integrated the RNA-sequencing data with matched DNA-methylation and NGS data. We also used multi-omics data from IDH-mutant astrocytomas included in the TCGA dataset and validated results on matched primary and recurrent samples from the GLASS-NL study. Since discrete classes do not adequately capture grading of these tumours, we utilised DNA-methylation profiles to generate a Continuous Grading Coefficient (CGC) based on classification scores from a CNS-tumour classifier. CGC was an independent predictor of survival outperforming current WHO-CNS5 and methylation-based classification. Our RNA-sequencing analysis revealed four distinct transcription clusters that were associated with (i) upregulation of cell cycling genes; (ii) downregulation of glial differentiation genes; (iii) upregulation of embryonic development genes (e.g. HOX, PAX, and TBX) and (iv) upregulation of extracellular matrix genes. The upregulation of embryonic development genes was associated with a specific increase of CpG island methylation near these genes. Higher grade IDH-mutant astrocytomas have DNA-methylation signatures that, on the RNA level, are associated with increased cell cycling, tumour cell de-differentiation and extracellular matrix remodelling. These combined molecular signatures can serve as an objective marker for grading of IDH-mutant astrocytomas.

CDKN2A Homozygous Deletion Is a Stronger Predictor of Outcome than IDH1/2-Mutation in CNS WHO Grade 4 Gliomas

Background: We primarily investigated the prognostic role of CDKN2A homozygous deletion in CNS WHO grade 4 gliomas. Additionally, we plan to examine traditional prognostic factors for grade 4 gliomas and validate the findings. Materials: We conducted a retrospective analysis of the glioma cohorts at our institute. We reviewed medical records spanning a 15-year period and examined pathological slides for an updated diagnosis according to the 2021 WHO classification of CNS tumors. We examined the IDH1/2 mutation and CDKN2A deletion using NGS analysis with ONCOaccuPanel®. Further, we examined traditional prognostic factors, including age, WHO performance status, extent of resection, and MGMT promoter methylation status. Results: The mean follow-up duration was 27.5 months (range: 4.1-43.5 months) and mean overall survival (OS) was 20.7 months (SD, ±1.759). After the exclusion of six patients with a poor status of pathologic samples, a total of 136 glioblastoma cases diagnosed by previous WHO classification criteria were newly classified into 29 (21.3%) astrocytoma, IDH-mutant, and CNS WHO grade 4 cases, and 107 (78.7%) glioblastoma, IDH-wildtype, and CNS WHO grade 4 cases. Among them, 61 (56.0%) had CDKN2A deletions. The high-risk group with CDKN2A deletion regardless of IDH1/2 mutation had a mean OS of 16.65 months (SD, ±1.554), the intermediate-risk group without CDKN2A deletion and with IDH1/2 mutation had a mean OS of 21.85 months (SD, ±2.082), and the low-risk group without CDKN2A deletion and with IDH1/2 mutation had a mean OS of 33.38 months (SD, ±2.946). Multifactor analysis showed that age (≥50 years vs. <50 years; HR 4.645), WHO performance (0, 1 vs. 2; HR 5.002), extent of resection (gross total resection vs. others; HR 5.528), MGMT promoter methylation, (methylated vs. unmethylated; HR 5.078), IDH1/2 mutation (mutant vs. wildtype; HR 6.352), and CDKN2A deletion (absence vs. presence; HR 13.454) were associated with OS independently. Conclusions: The present study suggests that CDKN2A deletion plays a powerful prognostic role in CNS WHO grade 4 gliomas. Even if CNS WHO grade 4 gliomas have mutant IDH1/2, they may have poor clinical outcomes because of CDKN2A deletion.

Patterns of intersectional tumor volumes in T2-weighted MRI and [18F]FET PET in adult glioma: a prospective, observational study

Brain tumor volumes as assessed by magnetic resonance imaging (MRI) do not always spatially overlap with biological tumor volumes (BTV) measured by [18F]Fluoroethyltyrosine positron emission tomography ([18F]FET PET). We prospectively investigated volumetric patterns based on the extent of tumor volume overlap between the two modalities. Eighty-six patients with newly diagnosed glioma who had undergone MRI and [18F]FET PET between 2007 and 2009 were included in this prospective study and (re-)classified according to CNS WHO 2021 (Classification of Tumors of the Central Nervous System by the World Health Organization). Four different patterns of volume overlap were defined mathematically according to the extent of overlap between MRI-based T2 tumor volume (non-enhancing tumor volume, nCEV) and BTVs. Progression-free (PFS) and overall survival (OS) were determined. Seventy patients were diagnosed with isocitrate dehydrogenase wildtype (IDHwt) glioblastoma and 16 with IDH-mutant glioma, respectively. The most common pattern was characterized by a larger non-contrast-enhancing tumor volume (nCEV) that enclosed all or most of the BTV and was observed in 46 patients (54%) (pattern 1). This pattern was more frequent in IDH-mutant gliomas than in IDH-wildtype glioblastoma (81% versus 47%, p = 0.02). In multivariate analyses, pattern 1 was associated with prolonged PFS (HR 0.59; 95 CI 0.34-1.0; p = 0.05), but not OS (HR 0.66; 95 CI 0.4-1.08; p = 0.1). For OS, presence of an IDH mutation (p = 0.05) and lower age (p = 0.03) were associated with prolonged OS. The spatial relation between nCEV and BTV varies within and between glioma entities. Most frequently, a larger nCEV encases the BTV. Some patients show spatially dissociated nCEVs and BTVs. Not accounting for this phenomenon in surgery or radiotherapy planning might lead to undertreatment.

The biological significance of tumor grade, age, enhancement, and extent of resection in IDH-mutant gliomas: How should they inform treatment decisions in the era of IDH inhibitors?

The 2016 and 2021 World Health Organization 2021 Classification of central nervous system tumors have resulted in a major improvement in the classification of isocitrate dehydrogenase (IDH)-mutant gliomas. With more effective treatments many patients experience prolonged survival. However, treatment guidelines are often still based on information from historical series comprising both patients with IDH wild-type and IDH-mutant tumors. They provide recommendations for radiotherapy and chemotherapy for so-called high-risk patients, usually based on residual tumor after surgery and age over 40. More up-to-date studies give a better insight into clinical, radiological, and molecular factors associated with the outcome of patients with IDH-mutant glioma. These insights should be used today for risk stratification and for treatment decisions. In many patients with IDH-mutant grades 2 and 3 glioma, if carefully monitored postponing radiotherapy and chemotherapy is safe, and will not jeopardize the overall outcome of patients. With the INDIGO trial showing patient benefit from the IDH inhibitor vorasidenib, there is a sizable population in which it seems reasonable to try this class of agents before recommending radio-chemotherapy with its delayed adverse event profile affecting quality of survival. Ongoing trials should help to further identify the patients that are benefiting from this treatment.

Molecular markers for pediatric low-grade glioma

Over the past decade, our understanding of the molecular drivers of pediatric low-grade glioma (PLGG) has expanded dramatically. These tumors are predominantly driven by RAS/MAPK pathway activating alterations (fusions and point mutations), most frequently in BRAF, FGFR1, and NF1. Furthermore, additional second hits in tumor suppressor genes (TP53, ATRX, CDKN2A) can portend more aggressive behaviour. Accordingly, comprehensive molecular profiling-specifically genetic sequencing, often plus copy number profiling-has become critical for guiding the diagnosis and management of PLGG. In this review, we discuss the most important genetic alterations that inform on classification and prognosis of PLGG, highlighting their diagnostic and therapeutic relevance.

In-house molecular diagnosis of diffuse glioma updating the revised WHO classification by a platform of the advanced medical care system, Senshin-Iryo

Since the World Health Organization (WHO) 2016 revision, the number of molecular markers required for diffuse gliomas has increased, placing a burden on clinical practice. We have established an in-house, molecular diagnostic platform using Senshin-Iryo, a feature of Japan's unique healthcare system, and partially modified the analysis method in accordance with the WHO 2021 revision. Herein, we review over a total 5 years of achievements using this platform. Analyses of IDH, BRAF, and H3 point mutations, loss of heterozygosity (LOH) on 1p/19q and chromosomes 10 and 17, and MGMT methylation were combined into a set that was submitted to Senshin-Iryo as "Drug resistance gene testing for anticancer chemotherapy" and was approved in August 2018. Subsequently, in October 2021, Sanger sequencing for the TERT promoter mutation was added to the set, and LOH analysis was replaced with multiplex ligation-dependent probe amplification (MLPA) to analyze 1p/19q codeletion and newly required genetic markers, such as EGFR, PTEN, and CDKN2A from WHO 2021. Among the over 200 cases included, 54 were analyzed after the WHO 2021 revision. The laboratory has maintained a diagnostic platform where molecular diagnoses are confirmed within 2 weeks. Initial expenditures exceeded the income from patient copayments; however, it has gradually been reduced to running costs alone and is approaching profitability. After the WHO 2021 revision, diagnoses were confirmed using molecular markers obtained from Senshin-Iryo in 38 of 54 cases (70.1%). Among the remaining 16 patients, only four (7.4%) were diagnosed with diffuse glioma, not elsewhere classified, which was excluded in 12 cases where glioblastoma was confirmed by histopathological diagnosis. Our Senshin-Iryo trial functioned as a salvage system to overcome the transition period between continued revisions of WHO classification that has caused a clinical dilemma in the Japanese healthcare system.

Clinical sequencing reveals diagnostic, therapeutic, and prognostic biomarkers for adult-type diffuse gliomas

Diffuse gliomas in adults are highly infiltrative and largely incurable. Whole exome sequencing (WES) has been demonstrated very useful in genetic analysis. Here WES was performed to characterize genomic landscape of adult-type diffuse gliomas to discover the diagnostic, therapeutic and prognostic biomarkers. Somatic and germline variants of 66 patients with adult-type diffuse gliomas were detected by WES based on the next-generation sequencing. TCGA and CGGA datasets were included to analyze the integrated diagnosis and prognosis. Among 66 patients, the diagnosis of 9 cases was changed, in which 8 cases of astrocytoma were corrected into IDH-wildtype glioblastoma (GBM), and 1 oligodendroglioma without 1p/19q co-deletion into astrocytoma. The distribution of mutations including ATRX/TP53 differed in three cohorts. The genetic mutations in GBM mainly concentrated on the cell cycle, PI3K and RTK pathways. The mutational landscape of astrocytoma was more similar to that of GBM, with the highest frequency in germline variants. Patients with IDH-mutant astrocytoma harboring SNVs of PIK3CA and PIK3R1 showed a significantly worse overall survival (OS) than wild-type patients. AEBP1 amplification was associated with shorter OS in GBM. Our study suggests that clinical sequencing can recapitulate previous findings, which may provide a powerful approach to discover diagnostic, therapeutic and prognostic markers for precision medicine in adult-type diffuse gliomas.

Refinement of prognostication for IDH-mutant astrocytomas using DNA methylation-based classification

The 2021 World Health Organization (WHO) grading system of isocitrate dehydrogenase (IDH)-mutant astrocytomas relies on histological features and the presence of homozygous deletion of the cyclin-dependent kinase inhibitor 2A and 2B (CDKN2A/B). DNA methylation profiling has become highly relevant in the diagnosis of central nervous system (CNS) tumors including gliomas, and it has been incorporated into routine clinical diagnostics in some countries. In this study, we, therefore, examined the value of DNA methylation-based classification for prognostication of patients with IDH-mutant astrocytomas. We analyzed histopathological diagnoses, genome-wide DNA methylation array data, and chromosomal copy number alteration profiles from a cohort of 385 adult-type IDH-mutant astrocytomas, including a local cohort of 127 cases and 258 cases from public repositories. Prognosis based on WHO 2021 CNS criteria (histological grade and CDKN2A/B homozygous deletion status), other relevant chromosomal/gene alterations in IDH-mutant astrocytomas and DNA methylation-based subclassification according to the molecular neuropathology classifier were assessed. We demonstrate that DNA methylation-based classification of IDH-mutant astrocytomas can be used to predict outcome of the patients equally well as WHO 2021 CNS criteria. In addition, methylation-based subclassification enabled the identification of IDH-mutant astrocytoma patients with poor survival among patients with grade 3 tumors and patients with grade 4 tumors with a more favorable outcome. In conclusion, DNA methylation-based subclassification adds prognostic information for IDH-mutant astrocytomas that can further refine the current WHO 2021 grading scheme for these patients.

Comparative analysis of molecular and histological glioblastomas: insights into prognostic variance

PURPOSE

Whether molecular glioblastomas (GBMs) identify with a similar dismal prognosis as a "classical" histological GBM is controversial. This study aimed to compare the clinical, molecular, imaging, surgical factors, and prognosis between molecular GBMs and histological GBMs.

METHODS

Retrospective chart and imaging review was performed in 983 IDH-wildtype GBM patients (52 molecular GBMs and 931 histological GBMs) from a single institution between 2005 and 2023. Propensity score-matched analysis was additionally performed to adjust for differences in baseline variables between molecular GBMs and histological GBMs.

RESULTS

Molecular GBM patients were substantially younger (58.1 vs. 62.4, P = 0.014) with higher rate of TERTp mutation (84.6% vs. 50.3%, P < 0.001) compared with histological GBM patients. Imaging showed higher incidence of gliomatosis cerebri pattern (32.7% vs. 9.2%, P < 0.001) in molecular GBM compared with histological GBM, which resulted in lesser extent of resection (P < 0.001) in these patients. The survival was significantly better in molecular GBM compared to histological GBM (median OS 30.2 vs. 18.4 months, P = 0.001). The superior outcome was confirmed in propensity score analyses by matching histological GBM to molecular GBM (P < 0.001).

CONCLUSION

There are distinct clinical, molecular, and imaging differences between molecular GBMs and histological GBMs. Our results suggest that molecular GBMs have a more favorable prognosis than histological GBMs.

T2-FLAIR mismatch sign, an imaging biomarker for CDKN2A-intact in non-enhancing astrocytoma, IDH-mutant

INTRODUCTION

The WHO classification of central nervous system tumors (5th edition) classified astrocytoma, IDH-mutant accompanied with CDKN2A/B homozygous deletion as WHO grade 4. Loss of immunohistochemical (IHC) staining for methylthioadenosine phosphorylase (MTAP) was developed as a surrogate marker for CDKN2A-HD. Identification of imaging biomarkers for CDKN2A status is of immense clinical relevance. In this study, we explored the association between radiological characteristics of non-enhancing astrocytoma, IDH-mutant to the CDKN2A/B status.

METHODS

Thirty-one cases of astrocytoma, IDH-mutant with MTAP results by IHC were included in this study. The status of CDKN2A was diagnosed by IHC staining for MTAP in all cases, which was further confirmed by comprehensive genomic analysis in 12 cases. The T2-FLAIR mismatch sign, cystic component, calcification, and intratumoral microbleeding were evaluated. The relationship between the radiological features and molecular pathological diagnosis was analyzed.

RESULTS

Twenty-six cases were identified as CDKN2A-intact while 5 cases were CDKN2A-HD. The presence of > 33% and > 50% T2-FLAIR mismatch was observed in 23 cases (74.2%) and 14 cases (45.2%), respectively, and was associated with CDKN2A-intact astrocytoma (p = 0.0001, 0.0482). None of the astrocytoma, IDH-mutant with CDKN2A-HD showed T2-FLAIR mismatch sign. Cystic component, calcification, and intratumoral microbleeding were not associated with CDKN2A status.

CONCLUSION

In patients with non-enhancing astrocytoma, IDH-mutant, the T2-FLAIR mismatch sign is a potential imaging biomarker for the CDKN2A-intact subtype. This imaging biomarker may enable preoperative prediction of CDKN2A status among astrocytoma, IDH-mutant.

Genetic and epigenetic instability as an underlying driver of progression and aggressive behavior in IDH-mutant astrocytoma

In recent years, the classification of adult-type diffuse gliomas has undergone a revolution, wherein specific molecular features now represent defining diagnostic criteria of IDH-wild-type glioblastomas, IDH-mutant astrocytomas, and IDH-mutant 1p/19q-codeleted oligodendrogliomas. With the introduction of the 2021 WHO CNS classification, additional molecular alterations are now integrated into the grading of these tumors, given equal weight to traditional histologic features. However, there remains a great deal of heterogeneity in patient outcome even within these established tumor subclassifications that is unexplained by currently codified molecular alterations, particularly in the IDH-mutant astrocytoma category. There is also significant intercellular genetic and epigenetic heterogeneity and plasticity with resulting phenotypic heterogeneity, making these tumors remarkably adaptable and robust, and presenting a significant barrier to the design of effective therapeutics. Herein, we review the mechanisms and consequences of genetic and epigenetic instability, including chromosomal instability (CIN), microsatellite instability (MSI)/mismatch repair (MMR) deficits, and epigenetic instability, in the underlying biology, tumorigenesis, and progression of IDH-mutant astrocytomas. We also discuss the contribution of recent high-resolution transcriptomics studies toward defining tumor heterogeneity with single-cell resolution. While intratumoral heterogeneity is a well-known feature of diffuse gliomas, the contribution of these various processes has only recently been considered as a potential driver of tumor aggressiveness. CIN has an independent, adverse effect on patient survival, similar to the effect of histologic grade and homozygous CDKN2A deletion, while MMR mutation is only associated with poor overall survival in univariate analysis but is highly correlated with higher histologic/molecular grade and other aggressive features. These forms of genomic instability, which may significantly affect the natural progression of these tumors, response to therapy, and ultimately clinical outcome for patients, are potentially measurable features which could aid in diagnosis, grading, prognosis, and development of personalized therapeutics.

Frailty in patients with IDH-mutant gliomas: experience from a high-volume tumor center

PURPOSE

Gliomas are increasingly diagnosed in an aging population, with treatment outcomes influenced by factors like tumor genetics and patient frailty. This study focused on IDH-mutant gliomas and assessed how frailty affects 30-day readmission and overall survival (OS). We aimed to address a gap in understanding the impact of frailty on this specific glioma subtype.

METHODS

136 patients with an IDH-mutant glioma between 2007 and 2021 were identified at our institution. High frailty was classified by scores ≥ 1 on the 5-factor modified frailty index (mFI-5) and ≥ 3 on the Charlson Comorbidity Index (CCI). Patient and tumor characteristics including age, sex, race, Karnofsky Performance Status (KPS), Body Mass Index (BMI), tumor type and location, type of operation, and therapy course were recorded. Outcomes measured included 30-day readmission and overall survival (OS). Analysis was conducted utilizing logistic regression and Kaplan-Meier curves.

RESULTS

Of the 136 patients, 52 (38%) had high frailty: 18 with CCI ≥ 3, 34 with mFI-5 ≥ 1. High frailty correlated with increased BMI (CCI: 30.2, mFI-5: 30.1 kg/m2), more neurological deficits (CCI: 61%, mFI-5: 56%), and older age at surgery (CCI: 63, mFI-5: 48 years). Hospital readmission within 30 days occurred in 8 (5.9%) patients. Logistic regression indicated no significant difference in 30-day readmission rates (CCI: p = 0.30, mFI-5: p = 0.62) or median OS between high and low frailty groups. However, patients treated at our institution with newly diagnosed tumors with high mFI-5 had a 6.79 times higher adjusted death hazard than those with low mFI-5 (p = .049).

CONCLUSION

Our analysis revealed that CCI and mFI-5 were not significantly associated with 30-day nor OS. However, in patients with non-recurrent tumors, there was a significant association of mFI-5 with OS. Further study of frailty with larger cohorts is warranted to enhance prognostication of outcome after neurosurgical treatment.

Availability and utilization of molecular testing for primary central nervous system tumors among US hospitals

Advanced molecular testing has increasingly become an integral component for accurate diagnosis of central nervous system (CNS) tumors. We sought to establish the current state of molecular testing availability and approaches for the diagnosis of CNS tumors in US hospitals that conduct high volumes of CNS tumor resections. We distributed a 16-item survey inquiring about molecular testing approaches for CNS tumors to 115 neuropathologists at US hospitals with neurosurgery residency programs. Thirty-five neuropathologists (30.4%) responded to the survey, all of whom indicated their institutions perform molecular testing on CNS tumor tissue. The most commonly offered tests were MGMT methylation profiling and next-generation sequencing. Fourteen respondents (40%) indicated that their institution is able to test for and report all of the molecular alterations included in our survey. Nine (25.7%) respondents indicated that molecular testing is performed as standard of care for all patients with resected CNS tumors. Our results suggest that even in academic hospitals with a high volume of CNS tumor resections, molecular testing for these tumors is limited. Continued initiatives are necessary to expand the availability of molecular testing for CNS tumors to ensure diagnostic accuracy and guide targeted therapy.

The 2021 World Health Organization Central Nervous System Tumor Classification: The Spectrum of Diffuse Gliomas

The 2021 edition of the World Health Organization (WHO) classification of central nervous system tumors introduces significant revisions across various tumor types. These updates, encompassing changes in diagnostic techniques, genomic integration, terminology, and grading, are crucial for radiologists, who play a critical role in interpreting brain tumor imaging. Such changes impact the diagnosis and management of nearly all central nervous system tumor categories, including the reclassification, addition, and removal of specific tumor entities. Given their pivotal role in patient care, radiologists must remain conversant with these revisions to effectively contribute to multidisciplinary tumor boards and collaborate with peers in neuro-oncology, neurosurgery, radiation oncology, and neuropathology. This knowledge is essential not only for accurate diagnosis and staging, but also for understanding the molecular and genetic underpinnings of tumors, which can influence treatment decisions and prognostication. This review, therefore, focuses on the most pertinent updates concerning the classification of adult diffuse gliomas, highlighting the aspects most relevant to radiological practice. Emphasis is placed on the implications of new genetic information on tumor behavior and imaging findings, providing necessary tools to stay abreast of advancements in the field. This comprehensive overview aims to enhance the radiologist's ability to integrate new WHO classification criteria into everyday practice, ultimately improving patient outcomes through informed and precise imaging assessments.

Case report: A 53-year-old woman with synchronous WHO classification II and IV gliomas

Introduction

Glioma is the most common primary intracranial neoplasm with a relatively poor prognosis.

Case presentation

Here, we present a unique case of a 53-year-old woman with two histopathologically distinct gliomas at the initial diagnosis. She presented with headaches and left limb weakness before admission, and magnetic resonance imaging (MRI) showed right frontal and basal ganglia area involvement combined with hemorrhage. The patient underwent a navigation-guided craniotomy for tumor removal. Pathological examination revealed the right frontal lobe lesion as a WHO grade II IDH-NOS astrocytoma, but the right parietal lobe lesion was a WHO grade IV IDH-mutant diffuse astrocytoma. Molecular detection of the parietal lesion revealed a point mutation at the R132 locus of the IDH1 gene, no mutation in the TERT promoter, amplification of the epidermal growth factor receptor, and a non-homozygous CDKN2A/B deletion.

Discussion

In-depth epigenomic analysis and molecular examination revealed that one patient had two different brain tumors, underscoring the importance of performing a comprehensive brain tumor workup.

Conclusion

This unique case confirms that adjacent astrocytomas may have different molecular pathogenesis and provides novel insights into the development of gliomas.

A viral attack on brain tumors: the potential of oncolytic virus therapy

Managing malignant brain tumors remains a significant therapeutic hurdle that necessitates further research to comprehend their treatment potential fully. Oncolytic viruses (OVs) offer many opportunities for predicting and combating tumors through several mechanisms, with both preclinical and clinical studies demonstrating potential. OV therapy has emerged as a potent and effective method with a dual mechanism. Developing innovative and effective strategies for virus transduction, coupled with immune checkpoint inhibitors or chemotherapy drugs, strengthens this new technique. Furthermore, the discovery and creation of new OVs that can seamlessly integrate gene therapy strategies, such as cytotoxic, anti-angiogenic, and immunostimulatory, are promising advancements. This review presents an overview of the latest advancements in OVs transduction for brain cancer, focusing on the safety and effectiveness of G207, G47Δ, M032, rQNestin34.5v.2, C134, DNX-2401, Ad-TD-nsIL12, NSC-CRAd-S-p7, TG6002, and PVSRIPO. These are evaluated in both preclinical and clinical models of various brain tumors.

Molecular Pathology of Gliomas

Gliomas are the most common adult and pediatric primary brain tumors. Molecular studies have identified features that can enhance diagnosis and provide biomarkers. IDH1/2 mutation with ATRX and TP53 mutations defines diffuse astrocytomas, whereas IDH1/2 mutations with 1p19q loss defines oligodendroglioma. Focal amplifications of receptor tyrosine kinase genes, TERT promoter mutation, and loss of chromosomes 10 and 13 with trisomy of chromosome 7 are characteristic features of glioblastoma and can be used for diagnosis. BRAF gene fusions and mutations in low-grade gliomas and histone H3 mutations in high-grade gliomas also can be used for diagnostics.

A Contemporary Approach to Intraoperative Evaluation in Neuropathology

CONTEXT.—

Although the basic principles of intraoperative diagnosis in surgical neuropathology have not changed in the last century, the last several decades have seen dramatic changes in tumor classification, terminology, molecular classification, and modalities used for intraoperative diagnosis. As many neuropathologic intraoperative diagnoses are performed by general surgical pathologists, awareness of these recent changes is important for the most accurate intraoperative diagnosis.

OBJECTIVE.—

To describe recent changes in the practice of intraoperative surgical neuropathology, with an emphasis on new entities, tumor classification, and anticipated ancillary tests, including molecular testing.

DATA SOURCES.—

The sources for this review include the fifth edition of the World Health Organization Classification of Tumours of the Central Nervous System, primary literature on intraoperative diagnosis and newly described tumor entities, and the authors' clinical experience.

CONCLUSIONS.—

A significant majority of neuropathologic diagnoses require ancillary testing, including molecular analysis, for appropriate classification. Therefore, the primary goal for any neurosurgical intraoperative diagnosis is the identification of diagnostic tissue and the preservation of the appropriate tissue for molecular testing. The intraoperative pathologist should seek to place a tumor in the most accurate diagnostic category possible, but specific diagnosis at the time of an intraoperative diagnosis is often not possible. Many entities have seen adjustments to grading criteria, including the incorporation of molecular features into grading. Awareness of these changes can help to avoid overgrading or undergrading at the time of intraoperative evaluation.