WHO’s arrived in 2016! An updated weather forecast for integrated brain tumor diagnosis

IDH1/2 Mutations in Patients With Diffuse Gliomas: A Single Centre Retrospective Massively Parallel Sequencing Analysis

Patients below 55 years were genetically studied because the prevalence of isocitrate dehydrogenase 1 (IDH1) decreases in older patients and on grounds of cost-effectiveness, as suggested by the World Health Organization (WHO) in 2016. The aim of our study was to use novel massively parallel sequencing (MPS) approaches to examine rare variants of IDH1/2 in Czech diffuse astrocytic and oligodendroglial tumors (gliomas) patients below 55 years of age who had been immunohistochemically (IHC) diagnosed as IDH1 R132H negative. The IHC IDH1 status (wild type or mutant) of 275 tissue samples was analyzed using antibodies against the IDH1 R132H protein. Sixty-three samples of 55 years old patients with IHC IDH1 WT status were genotyped using two different MPS technologies to detect rare IDH1 and IDH2 variants. The tiered IHC (60 positive) and molecular (10 positive) approach thus revealed that 70 of the 275 samples (25%) bore IDH1/IDH2 mutations. The combined molecular and IHC approach thus revealed that 70 of the 275 samples (25%) considered in the study bore IDH1/IDH2 mutations. IHC detection of the IDH1 R132H variant should be routinely complemented with MPS to detect rare IDH1/2 variants in glioma patients below 55 years of age with negative IHC result of IDH R132H variant.

Foxr2 promotes formation of CNS-embryonal tumors in a Trp53-deficient background

BACKGROUND

Embryonal tumors in the central nervous system (CNS) are primary, aggressive, and poorly differentiated pediatric brain tumors. We identified forkhead box R2 (Foxr2) as an oncogene for medulloblastoma through a transposon-based insertional mutagenesis screen. Foxr2 translocation has been identified in a subset of human embryonal tumors of the CNS, designated as CNS neuroblastoma with Foxr2 activation (CNS NB-Foxr2); however, the in vivo functions of Foxr2 remain elusive.

METHODS

We analyzed the effect of Foxr2 overexpression in the mouse brain by generating a transgenic strain that expresses Foxr2 in the entire brain under a transformation related protein 53 (Trp53)-deficient background. We performed histological analysis of tumors and characterized tumor-derived sphere-forming cells. We investigated gene expression profiles of tumor-derived cells.

RESULTS

Foxr2 and Trp53 loss promoted tumor formation in the olfactory bulb (OB) and brainstem (BS). The tumors showed the common morphological features of small round blue cell tumors, exhibiting divergent, mainly neuronal and glial, patterns of differentiation, which corresponds to the definition of CNS-embryonal tumors. Importantly, all mice developed CNS-embryonal tumors. In the OB, early proliferative lesions consisting of oligodendrocyte transcription factor 2 (Olig2+) cells were observed, indicating that Foxr2 expression expanded Olig2+ cells in the OB. Tumor-derived cells formed spheres in vitro and induced tumors that recapitulated the parental tumor upon transplantation, indicating the presence of tumor-initiating cells. Gene expression profiling revealed that OB and BS tumor cells were enriched for the expression of the genes specific to CNS NB-Foxr2.

CONCLUSION

Our data demonstrate that Foxr2 plays a causative role in the formation of CNS-embryonal tumors.

Testing for causality between systematically identified risk factors and glioma: a Mendelian randomization study

BACKGROUND

Whilst epidemiological studies have provided evidence of associations between certain risk factors and glioma onset, inferring causality has proven challenging. Using Mendelian randomization (MR), we assessed whether associations of 36 reported glioma risk factors showed evidence of a causal relationship.

METHODS

We performed a systematic search of MEDLINE from inception to October 2018 to identify candidate risk factors and conducted a meta-analysis of two glioma genome-wide association studies (5739 cases and 5501 controls) to form our exposure and outcome datasets. MR analyses were performed using genetic variants to proxy for candidate risk factors. We investigated whether risk factors differed by subtype diagnosis (either glioblastoma (n = 3112) or non-glioblastoma (n = 2411)). MR estimates for each risk factor were determined using multiplicative random effects inverse-variance weighting (IVW). Sensitivity analyses investigated potential pleiotropy using MR-Egger regression, the weighted median estimator, and the mode-based estimator. To increase power, trait-specific polygenic risk scores were used to test the association of a genetically predicated increase in each risk factor with glioma onset.

RESULTS

Our systematic search identified 36 risk factors that could be proxied using genetic variants. Using MR, we found evidence that four genetically predicted traits increased risk of glioma, glioblastoma or non-glioblastoma: longer leukocyte telomere length, liability to allergic disease, increased alcohol consumption and liability to childhood extreme obesity (> 3 standard deviations from the mean). Two traits decreased risk of non-glioblastoma cancers: increased low-density lipoprotein cholesterol (LDLc) and triglyceride levels. Our findings were similar across sensitivity analyses that made allowance for pleiotropy (genetic confounding).

CONCLUSIONS

Our comprehensive investigation provides evidence of a causal link between both genetically predicted leukocyte telomere length, allergic disease, alcohol consumption, childhood extreme obesity, and LDLc and triglyceride levels, and glioma. The findings from our study warrant further research to uncover mechanisms that implicate these traits in glioma onset.

Diffuse gliomas to date and beyond 2016 WHO Classification of Tumours of the Central Nervous System

The updated 2016 World Health Organization (WHO) Classification of Tumours of the Central Nervous System (CNS) has incorporated molecular parameters into pathological diagnosis, for the first time in the molecular era. While it has led to the more precise diagnoses of well-understood entities and the better comprehension of less-understood entities, its practical application has also created some concerns whether or not genotypes predominate over phenotypes in tumor diagnostics. In response to these concerns, the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy-Not Official WHO (cIMAPCT-NOW) was established under the sponsorship of the International Society of Neuropathology to provide a forum to evaluate and recommend proposed changes to future CNS tumor classifications. cIMPACT has thus far published five updates on the proposal and clarification of existing and new terms and entities. Also, recent studies have shown that WHO grading based on histology has lost its prognostic relevance, which necessitates novel, improved grading criteria. We herein highlight the current status of clinical application of WHO 2016 classification and cIMPACT proposals, and the future endeavor to incorporate DNA methylation profiling of the CNS tumors for better clinical decision-making to achieve a goal of precision medicine for each patient with brain tumors.

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.

Elevated TERT Expression in TERT-Wildtype Adult Diffuse Gliomas: Histological Evaluation with a Novel TERT-Specific Antibody

Telomerase reverse transcriptase (TERT) is important for the biology of diffuse gliomas. TERT promoter mutations are selectively observed among 1p/19q-codeleted oligodendrogliomas and isocitrate dehydrogenase gene- (IDH-) wildtype glioblastoma (GBM). However, TERT transcripts range widely in various cancers including gliomas, and TERT protein expression has been rarely investigated thus far. It would be thus critical to examine the expression level of TERT in tumors in addition to its mutational status, and sensitive and specific methods are urgently needed to examine TERT protein expression for the assessment of TERT biology in gliomas. Using our newly developed TERT-specific monoclonal antibody (TMab-6) applicable to human tissue, we found an unexpected increase in TERT expression in TERT-wildtype as well as TERT-mutated gliomas and in tumor vasculature. This is the first extensive analysis on the expression of TERT immunoreactivity in human glioma tissue, suggesting that TERT protein expression may be regulated by several mechanisms in addition to its promoter mutation.

Spinal Cord Astrocytoma with Isocitrate Dehydrogenase 1 Gene Mutation

BACKGROUND

In 2016, the World Health Organization updated its classification of tumors, adding genetic profiles to the conventional histopathologic typing.

CASE DESCRIPTION

The authors present herein the first case of a 44-year-old female with isocitrate dehydrogenase-mutant World Health Organization grade II diffuse spinal astrocytoma diagnosed on the basis of both histopathologic and genetic findings.

CONCLUSIONS

The present case underscores the significant role of a molecular genetic analysis in the differential diagnosis of intramedullary spinal gliomas.

Treatment Recommendations for Adult Patients with Diffuse Gliomas of Grades II and III According to the New WHO Classification in 2016

With advanced understanding of molecular background and correlation with therapeutic outcomes, the revised 4th edition of World Health Organization (WHO) classification of central nervous system (CNS) tumors incorporated molecular information into the definition of diffuse gliomas. Indeed, oligodendroglioma and astrocytoma are now defined by molecular signature, with diagnosis of glioblastoma being made by histology. In parallel, numerous clinical trials are underway all over the world, and important findings are being produced every year that have an impact on patient outcomes. Moreover, novel therapies/technologies are also being actively developed; however, there are still many CNS tumors for which no effective therapy has been established except radiotherapy. In this article, the authors review the recent results of major clinical trials and present their treatment recommendations for patients with adult, supratentorial diffuse gliomas of grades II and III stratified according to the new WHO classification.

The 2016 WHO Classification of Tumours of the Central Nervous System: The Major Points of Revision

The updated 2016 edition of the World Health Organization (WHO) Classification of Tumours of the Central Nervous System (CNS) uses molecular parameters and the histology to define the main tumor categories for the first time. This represents a shift from the traditional principle of using neuropathological diagnoses, which are primarily based on the microscopic features, to using molecularly-oriented diagnoses. Major restructuring was made with regard to diffuse gliomas, medulloblastomas and other embryonal tumors. New entities that are defined by both the histological and molecular features include glioblastoma, isocitrate dehydrogenase (IDH)-wildtype and glioblastoma, IDH-mutant; diffuse midline glioma, H3 K27M-mutant; RELA fusion-positive ependymoma; medulloblastoma, wingless (WNT)-activated and medulloblastoma, sonic hedgehog (SHH)-activated; and embryonal tumor with multilayered rosettes, C19MC-altered. In addition, some entities that are no longer diagnostically relevant—such as CNS-primitive neuroectodermal tumor—have been deleted from this updated edition. The WHO2016 certainly facilitates clinical and basic research to improve the diagnosis of brain tumors and patient care.

Pathology of oligodendroglia: An overview

Oligodendroglia are cells responsible for creating myelin sheaths for axons in the CNS. However, pathologies of oligodendroglia other than demyelination are not well understood due to the lack of adequate methods of characterizing pathological conditions affecting oligodendroglia in human tissue. This review discusses three major topics with the aim of clarifying some of the controversies in the study of oligodendroglia. The oligodendroglioma, a relatively indolent form of diffuse gliomas thought to originate in oligodendrocytes, has never demonstrated myelin formation on electron microscopy nor shown a constant expression of myelin-related proteins. Oligodendrogliomas instead share an immune phenotype with oligodendrocyte progenitor cells (OPCs). Another type of cell that resembles OPCs are oligodendroglia-like cells (OLCs), which occur in many types of low-grade tumors and focal cortical dysplasia. In neurodegenerative disorders, oligodendroglia can be a target of abnormal aggregations of proteins such as tau. Tau-positive oligodendroglial inclusions in progressive supranuclear palsy and corticobasal generation differ from each other morphologically, ultrastructurally and biochemically, suggesting disparate underlying pathological processes despite significant overlapping of the clinical manifestations. To promote the study of oligodendroglia, novel methods for detecting OLCs in situ are urgently required.