Updating the grading criteria for adult diffuse gliomas: beyond the WHO2016CNS classification

Integrated assessment of malignancy in IDH-mutant astrocytoma with p16 and methylthioadenosine phosphorylase immunohistochemistry

In the fifth edition of the World Health Organization's (WHO) classification of tumors of the central nervous system (CNS), molecular analysis is required for not only determining each tumor type but assessing its prognosis based on malignancy (CNS WHO grade). A notable example is the loss of tumor suppressor gene cyclin-dependent kinase inhibitor 2A (CDKN2A), and CDKN2A homozygous deletion (HD) is a novel CNS WHO grade 4 marker in isocitrate dehydrogenase gene (IDH)-mutant astrocytoma. However, incorporating molecular workup into the "routine diagnostics" of each brain tumor type remains a major challenge, especially in resource-limited settings, including low- and middle-income countries. We herein validated the usefulness of p16 and methylthioadenosine phosphorylase (MTAP) immunohistochemistry (IHC) as potential surrogates for the assessment of CDKN2A status in 20 IDH-mutant astrocytoma cases. Of note, loss or retention of p16 and MTAP could accurately predict CDKN2A HD (p16: 87.5%, MTAP: 88.9%) or non-HD (p16: 100%, MTAP: 100%) with a single marker alone. Importantly, we revealed contributing factors to gray-zone IHC results (p16: 5-20%, MTAP: mosaic), including (1) hemizygous deletion of CDKN2A, (2) degenerative findings, and (3) intratumoral CDKN2A HD heterogeneity, the detailed histologic and molecular assessment of which would be a key to achieving integrated assessment of malignancy in IDH-mutant astrocytoma. We characterized the pitfalls of each method and provided for the first time a practical flowchart of astrocytoma grading, contributing to a normalization of WHO2021-based molecular diagnostics in resource-limited settings.

What Changed in CNS5? A Mini-Review on General Changes and Adult Diffuse Gliomas

The fifth edition of the WHO classification of tumors of the central nervous system (WHO CNS5) was published in 2021 which is the sixth version of the international standard for the diagnostics of CNS tumors. Regular updates of the consortium to inform molecular and practical approaches to CNS tumor taxonomy (cIMPACT-NOW) shaped the WHO CNS5 which continues the trend of incorporating the molecular characteristics of tumors into the histological and immunohistochemical findings. The various updates can be classified into general changes across all tumors and specific changes within the tumor groups. This mini-review highlights the general changes and the major changes in adult diffuse gliomas.

Emerging Materials, Wearables, and Diagnostic Advancements in Therapeutic Treatment of Brain Diseases

Among the most critical health issues, brain illnesses, such as neurodegenerative conditions and tumors, lower quality of life and have a significant economic impact. Implantable technology and nano-drug carriers have enormous promise for cerebral brain activity sensing and regulated therapeutic application in the treatment and detection of brain illnesses. Flexible materials are chosen for implantable devices because they help reduce biomechanical mismatch between the implanted device and brain tissue. Additionally, implanted biodegradable devices might lessen any autoimmune negative effects. The onerous subsequent operation for removing the implanted device is further lessened with biodegradability. This review expands on current developments in diagnostic technologies such as magnetic resonance imaging, computed tomography, mass spectroscopy, infrared spectroscopy, angiography, and electroencephalogram while providing an overview of prevalent brain diseases. As far as we are aware, there hasn't been a single review article that addresses all the prevalent brain illnesses. The reviewer also looks into the prospects for the future and offers suggestions for the direction of future developments in the treatment of brain diseases.

Role of Transmembrane Water Exchange in Glioma Invasion/Migration: In Vivo Preclinical Study by Relaxometry at Very Low Magnetic Field

This work shows that the longitudinal relaxation differences observed at very low magnetic fields between invasion/migration and proliferation processes on glioma mouse models in vivo are related to differences in the transmembrane water exchange basically linked to the aquaporin expression changes. Three glioma mouse models were used: Glio6 and Glio96 as invasion/migration models and U87 as cell proliferation model. In vivo proton longitudinal relaxation-rate constants (R1) at very low fields were measured by fast field cycling NMR (FFC-NMR). The tumor contribution to the observed proton relaxation rate, R1tum (U87: 12.26 ± 0.64 s−1; Glio6: 3.76 ± 0.88 s−1; Glio96: 6.90 ± 0.64 s−1 at 0.01 MHz), and the intracellular water lifetime, τin (U87: 826 ± 19 ms; Glio6: 516 ± 8 ms; Glio96: 596 ± 15 ms), were found to be good diagnostic hallmarks to distinguish invasion/migration from proliferation (p < 0.01 and 0.001). Overexpression of AQP4 and AQP1 were assessed in invasion/migration models, highlighting the pathophysiological role of these two aquaporins in water exchange that, in turn, determine the lower values in the observed R1 relaxation rate constant in glioma invasion/migration. Overall, our findings demonstrate that τin and R1 (measured at very low fields) are relevant biomarkers, discriminating invasion/migration from proliferation in vivo. These results highlight the use of FFC-NMR and FFC-imaging to assess the efficiency of drugs that could modulate aquaporin functions.

Molecular Aberrations Stratify Grade 2 Astrocytomas Into Several Rare Entities: Prognostic and Therapeutic Implications

The identification of specific molecular aberrations guides the prognostic stratification and management of grade 2 astrocytomas. Mutations in isocitrate dehydrogenase (IDH) 1 and 2, found in the majority of adult diffuse low-grade glioma (DLGG), seem to relate to a favorable prognosis compared to IDH wild-type (IDH-wt) counterparts. Moreover, the IDH-wt group can develop additional molecular alterations worsening the prognosis, such as epidermal growth factor receptor amplification (EGFR-amp) and mutation of the promoter of telomerase reverse transcriptase (pTERT-mut). This review analyzes the prognostic impact and therapeutic implications of genetic alterations in adult LGG.

Grading of adult diffuse gliomas according to the 2021 WHO Classification of Tumors of the Central Nervous System

The grading of gliomas based on histological features has been a subject of debate for several decades. A consensus has not yet been reached because of technical limitations and inter-observer variations. While the traditional grading system has failed to stratify the risk of IDH-mutant astrocytoma, canonical histological and proliferative markers may be applicable to the risk stratification of IDH-wild-type astrocytoma. Numerous studies have examined molecular markers in order to obtain more clinically relevant information that will improve the risk stratification of gliomas. The CDKN2A/B homozygous deletion for IDH-mutant astrocytoma and the following three criteria for IDH-wild-type astrocytoma: the concurrent gain of whole chromosome 7 and loss of whole chromosome 10, TERT promoter mutations, and EGFR amplification, were identified as independent molecular markers of the worst clinical outcomes. Therefore, the 2021 World Health Organization (WHO) Classification of Tumors of the Central Nervous System adopted these molecular markers into the revised grading criteria of IDH-mutant and -wild-type astrocytoma, respectively, as a grading system within tumor types. Of note, several recent studies have shown that some low-grade IDH-wild-type astrocytoma lacking both the molecular glioblastoma signature and genetic alterations typical of pediatric-type gliomas may demonstrate a relatively indolent clinical course, suggesting the existence of lower-grade adult IDH-wild-type astrocytoma. In terms of oligodendroglioma, IDH-mutant, and 1p/19q codeleted, consistent makers that predict poor outcomes have not yet been identified, and, thus, the current criteria have remained unchanged. Molecular testing to fulfill the revised WHO criteria is, however, not always available worldwide, and in that case, an integrated diagnosis combining all available complementary information is highly recommended. This review discusses controversial issues surrounding legacy grading systems and newly identified potential genetic markers of adult diffuse gliomas and provides perspectives on future grading systems.

WHO Grade Loses Its Prognostic Value in Molecularly Defined Diffuse Lower-Grade Gliomas

BACKGROUND

While molecular insights to diffuse lower-grade glioma (dLGG) have improved the basis for prognostication, most established clinical prognostic factors come from the pre-molecular era. For instance, WHO grade as a predictor for survival in dLGG with isocitrate dehydrogenase (IDH) mutation has recently been questioned. We studied the prognostic role of WHO grade in molecularly defined subgroups and evaluated earlier used prognostic factors in the current molecular setting.

MATERIAL AND METHODS

A total of 253 adults with morphological dLGG, consecutively included between 2007 and 2018, were assessed. IDH mutations, codeletion of chromosomal arms 1p/19q, and cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) deletions were analyzed.

RESULTS

There was no survival benefit for patients with WHO grade 2 over grade 3 IDH-mut dLGG after exclusion of tumors with known CDKN2A/B homozygous deletion (n=157) (log-rank p=0.97). This was true also after stratification for oncological postoperative treatment and when astrocytomas and oligodendrogliomas were analyzed separately. In IDH-mut astrocytomas, residual tumor volume after surgery was an independent prognostic factor for survival (HR 1.02; 95% CI 1.01-1.03; p=0.003), but not in oligodendrogliomas (HR 1.02; 95% CI 1.00-1.03; p=0.15). Preoperative tumor size was an independent predictor in both astrocytomas (HR 1.03; 95% CI 1.00-1.05; p=0.02) and oligodendrogliomas (HR 1.05; 95% CI 1.01-1.09; p=0.01). Age was not a significant prognostic factor in multivariable analyses (astrocytomas p=0.64, oligodendrogliomas p=0.08).

CONCLUSION

Our findings suggest that WHO grade is not a robust prognostic factor in molecularly well-defined dLGG. Preoperative tumor size remained a prognostic factor in both IDH-mut astrocytomas and oligodendrogliomas in our cohort, whereas residual tumor volume predicted prognosis in IDH-mut astrocytomas only. The age cutoffs for determining high risk in patients with IDH-mut dLGG from the pre-molecular era are not supported by our results.

Radiologic-pathologic association of tumor-like lesions with inflammation in cerebral white matter: Comparison of two cases with distinct clinical outcomes

Here, we report two cases showing tumor-like white matter lesions; one case was diagnosed as having inflammatory disease, and the other was diagnosed as having astrocytoma. Their outcomes were completely distinct despite similar pathology. Prior to biopsy, perfusion computed tomography (CT) and magnetic resonance imaging (MRI) were conducted. The two mass-forming lesions were distinct in edema level and vascularity patterns on CT and MRI. However, pathological examination of brain biopsy specimens revealed commonalities, including (1) proliferation of glial cells, (2) perivascular lymphocytic infiltration, and (3) appearance of numerous macrophages. Although atypical astrocytes proliferated in both cases, nuclear atypia was more distinct in case 2 than in case 1. The immunohistochemical results were the same for both cases: isocitrate dehydrogenase 1 (IDH1) R132H mutation was negative, and alpha thalassaemia mental retardation X-linked (ATRX) was retained. Faint immunoreactivity for p53 was observed in a few glial cells, and Ki-67 immunoreactive cells were markedly reduced in numbers (< 1%). Inflammatory reactions were evident in both cases: T cells dominantly infiltrated over B cells in the perivascular area in case 1, whereas both T and B cells infiltrated in case 2. Molecular analysis revealed wild-type IDH1 and IDH2 in both cases. However, a telomerase reverse transcriptase (TERT) sequence mutation was detected in case 2 but not in case 1. Eventually, case 1 was diagnosed as having inflammatory lesions, whereas case 2 was diagnosed as having diffuse astrocytoma associated with inflammatory reactions. The prognosis was favorable for case 1, whereas case 2 died 10 months following biopsy. These data indicated the diagnostic value of molecular analysis, for example, a TERT mutation, in association with the radiological findings. Although in case 2, histopathological evidence did not suggest high-grade glioma, the case met the new diagnostic criteria: "diffuse astrocytic glioma, IDH wild-type, with molecular features of glioblastoma, World Health Organization (WHO) grade IV," according to cIMPACT-NOW, update 3. Thus, interdisciplinary approaches are essential for accurate diagnosis of newly categorized white matter diseases.

Novel Concepts of Glioblastoma Therapy Concerning Its Heterogeneity

Although treatment outcomes of glioblastoma, the most malignant central nervous system (CNS) tumor, has improved in the past decades, it is still incurable, and survival has only slightly improved. Advances in molecular biology and genetics have completely transformed our understanding of glioblastoma. Multiple classifications and different diagnostic methods were made according to novel molecular markers. Discovering tumor heterogeneity only partially explains the ineffectiveness of current anti-proliferative therapies. Dynamic heterogeneity secures resistance to combined oncotherapy. As tumor growth proceeds, new therapy-resistant sub clones emerge. Liquid biopsy is a new and promising diagnostic tool that can step up with the dynamic genetic change. Getting a 'real-time' picture of a specific tumor, anti-invasion and multi-target treatment can be designed. During invasion to the peri-tumoral brain tissue, glioma cells interact with the extracellular matrix components. The expressional levels of these matrix molecules give a characteristic pattern, the invasion spectrum, which possess vast diagnostical, predictive and prognostic information. It is a huge leap forward combating tumor heterogeneity and searching for novel therapies. Using the invasion spectrum of a tumor sample is a novel tool to distinguish between histological subtypes, specifying the tumor grades or different prognostic groups. Moreover, new therapeutic methods and their combinations are under trial. These are crucial steps towards personalized oncotherapy.

Clinical implications of molecular analysis in diffuse glioma stratification

The revised 4th edition of the 2016 World Health Organization Classification of Tumors of the Central Nervous System (2016 CNS WHO) has introduced the integrated diagnostic classification that combines molecular and histological diagnoses for diffuse gliomas. In this study, we evaluated the molecular alterations for consecutive 300 diffuse glioma cases (grade 2, 56; grade 3, 62; grade 4, 182) based on this classification. Mutations in the isocitrate dehydrogenase (IDH) genes were common in lower grade glioma (LGG: grade2-3), and when combined with 1p/19q status, LGGs could be stratified into three groups except for four cases (Astrocytoma, IDH-mutant: 44; Oligodendroglioma, IDH-mutant and 1p/19q codeleted: 37; Astrocytoma, IDH-wildtype: 33). 1p/19q-codeleted oligodendrogliomas were clinically the most favorable subgroup even with upfront chemotherapy. In contrast, IDH-wildtype astrocytomas had a relatively worse prognosis; however, this subgroup was more heterogeneous. Of this subgroup, 11 cases had TERT promoter (pTERT) mutation with shorter overall survival than 12 pTERT-wildtype cases. Additionally, a longitudinal analysis indicated pTERT mutation as early molecular event for gliomagenesis. Therefore, pTERT mutation is critical for the diagnosis of molecular glioblastoma (WHO grade 4), regardless of histological findings, and future treatment strategy should be considered based on the precise molecular analysis.

IDH-wildtype lower-grade diffuse gliomas: the importance of histological grade and molecular assessment for prognostic stratification

BACKGROUND

Isocitrate dehydrogenase (IDH) wildtype (wt) grade II gliomas are a rare and heterogeneous entity. Survival and prognostic factors are poorly defined.

METHODS

We searched retrospectively all patients diagnosed with diffuse World Health Organization (WHO) grades II and III gliomas at our center (1989-2020).

RESULTS

Out of 517 grade II gliomas, 47 were "diffuse astrocytomas, IDHwt." Tumors frequently had fronto-temporo-insular location (28/47, 60%) and infiltrative behavior. We found telomerase reverse transcriptase (TERT) promoter mutations (23/45, 51%), whole chromosome 7 gains (10/37, 27%), whole chromosome 10 losses (10/41, 24%), and EGFR amplifications (4/43, 9%), but no TP53 mutations (0/22, 0%). Median overall survival (OS) was 59 months (vs 19 mo for IDHwt grade III gliomas) (P < 0.0001). Twenty-nine patients (29/43, 67%) met the definition of molecular glioblastoma according to cIMPACT-NOW update 3. Median OS in this subset was 42 months, which was shorter compared with patients with IDHwt grade II gliomas not meeting this definition (median OS: 57 mo), but substantially longer compared with IDHwt grade III gliomas meeting the definition for molecular glioblastoma (median OS: 17 mo, P < 0.0001). Most patients with IDHwt grade II gliomas met cIMPACT criteria because of isolated TERT promoter mutations (16/26, 62%), which were not predictive of poor outcome (median OS: 88 mo). Actionable targets, including 5 gene fusions involving FGFR3, were found in 7 patients (24%).

CONCLUSIONS

Our findings highlight the importance of histological grading and molecular profiling for the prognostic stratification of IDHwt gliomas and suggest some caution when assimilating IDHwt grade II gliomas to molecular glioblastomas, especially those with isolated TERT promoter mutation.

Chemoprevention and therapeutic role of essential oils and phenolic compounds: Modeling tumor microenvironment in glioblastoma

Glioblastoma (GBM) is the most common primary tumor of the central nervous system. Current treatments available for GBM entails surgical resection followed by temozolomide chemotherapy and/or radiotherapy, which are associated with multidrug resistance and severe side effects. While this treatment could yield good results, in almost all cases, patients suffer from relapse, which leads to reduced survival rates. Thus, therapeutic approaches with improved efficiency and reduced off-target risks are needed to overcome these problems. Regarding this, natural products appear as a safe and attractive strategy as chemotherapeutic agents or adjuvants in the treatment of GBM. Besides the increasing role of natural compounds for chemoprevention of GBM, it has been proposed to prevent carcinogenesis and metastasis of GBM. Numerous investigations showed that natural products are able to inhibit proliferation and angiogenesis, to induce apoptosis, and to target GBM stem cells, which are associated with tumor development and recurrence. This review gives a timely and comprehensive overview of the current literature regarding chemoprevention and therapy of GBM by natural products with a focus on essential oils and phenolic compounds and their molecular mechanisms.

Primary spinal intramedullary Ewing-like sarcoma harboring CIC-DUX4 translocation: a similar cytological appearance as its soft tissue counterpart but no lobulation in association with desmoplastic stroma

The CIC-DUX4 translocation is the most common genetic alteration of small round cell sarcomas without EWSR1 rearrangement. These "Ewing-like sarcomas" usually occur in peripheral soft tissues, and rare primary central nervous system (CNS) tumors have been described. We report a rare case of primary spinal intramedullary Ewing-like sarcoma harboring CIC-DUX4 translocation. A 23-year-old man presented with weakness in the extremities. Magnetic resonance imaging revealed a large intramedullary tumor spanning C3-C5 with heterogeneous enhancement following gadolinium administration. Histologically, most of the tumor displayed dense myeloid proliferation composed of medium- to slightly small-sized primitive cells. Postoperatively, he received local adjuvant radiation therapy without tumor progression for 10 months. Target RNA sequencing analysis revealed the CIC-DUX4 fusion gene. Methylation array analysis resulted in a diagnosis of "methylation class CNS Ewing sarcoma family tumor with CIC alteration". Although this tumor lacked characteristic histological features such as lobular structures in association with desmoplastic stroma, relatively uniform nuclei with prominent nucleoli and eosinophilic cytoplasm, which are often found in CIC-rearranged sarcomas of soft tissue, were identified. Recently, many CNS and soft tissue tumors require genetic analysis for precise diagnosis. To consider certain molecular testing, careful histological examination is essential.