Cerebellar glioblastoma: a clinical series with contemporary molecular analysis

Isocitrate Dehydrogenase (IDH)-Mutant High-Grade Glioma in the Cerebellum: A Case Report

High-grade glial cancers typically arise in the cerebral hemisphere and rarely in the cerebellum. Our objective was to highlight the diagnostic features of isocitrate dehydrogenase (IDH)-mutant high-grade gliomas in the cerebellum. We present a case of an elderly patient admitted with giddiness who was diagnosed with IDH-mutant high-grade glioma in the cerebellum, presenting as multiple lesions. We evaluated an open biopsy specimen to arrive at a diagnosis and used molecular studies to confirm the diagnosis and further categorize the specimens. Histopathology and immunohistochemistry confirmed the diagnosis of IDH-mutant high-grade glioma in the cerebellum.

A common tumour in a rare location: a single centre case series of cerebellar glioblastoma

Although glioblastoma is the commonest primary brain tumour in adults, its location in the cerebellum is extremely rare. We present thirteen cases (3 female, 10 male; median age at presentation 56 [age range 21-77]) of surgically managed, histologically confirmed, primary cerebellar glioblastoma (cGB) over a 17 year period (2005-2022). Pre-operative radiological diagnosis was challenging given cGB rarity, although MRI demonstrated ring enhancement in all cases. Surgical management included posterior fossa craniectomy and debulking in 11 cases and burr hole biopsy in two. CSF diversion was necessary in four cases. No evidence of IDH or ATRX gene mutations was found when tested. Survival ranged from 1 to 22 months after diagnosis (mean 10.9 months). We also seek to understand why glioblastoma is rare in this location and discuss potential reasons for this. We hypothesise that increasing anatomical distance from germinal regions and decreased local endogenous neural stem cell activity (which has been associated with glioblastoma) may explain why glioblastoma is rare in the cerebellum. We hereby seek to add to the limited literature on cGB as this is the largest UK cGB series to date.

Radiotherapy-induced glioblastoma: distinct differences in overall survival, tumor location, pMGMT methylation and primary tumor epidemiology in Hong Kong chinese patients

INTRODUCTION

Radiotherapy-induced glioblastomas (RIGB) are a well-known late and rare complication of brain irradiation. Yet the clinical, radiological and molecular characteristics of these tumors are not well characterized.

METHODS

This was a retrospective multicentre study that analysed adult patients with newly diagnosed glioblastoma over a 10-year period. Patients with RIGB were identified according to Cahan's criteria for radiation-induced tumors. A case-control analysis was performed to compare known prognostic factors for overall survival (OS) with an independent cohort of IDH-1 wildtype de novo glioblastomas treated with standard temozolomide chemoradiotherapy. Survival analysis was performed by Cox proportional hazards regression.

RESULTS

A total of 590 adult patients were diagnosed with glioblastoma. 19 patients (3%) had RIGB. The mean age of patients upon diagnosis was 48 years ± 15. The mean latency duration from radiotherapy to RIGB was 14 years ± 8. The mean total dose was 58Gy ± 10. One-third of patients (37%, 7/19) had nasopharyngeal cancer and a fifth (21%, 4/19) had primary intracranial germinoma. Compared to a cohort of 146 de novo glioblastoma patients, RIGB patients had a shorter median OS of 4.8 months versus 19.2 months (p-value: <.001). Over a third of RIGBs involved the cerebellum (37%, 7/19) and was higher than the control group (4%, 6/146; p-value: <.001). A fifth of RIGBs (21%, 3/19) were pMGMT methylated which was significantly fewer than the control group (49%, 71/146; p-value: .01). For RIGB patients (32%, 6/19) treated with re-irradiation, the one-year survival rate was 67% and only 8% for those without such treatment (p-value: .007).

CONCLUSION

The propensity for RIGBs to develop in the cerebellum and to be pMGMT unmethylated may contribute to their poorer prognosis. When possible re-irradiation may offer a survival benefit. Nasopharyngeal cancer and germinomas accounted for the majority of original malignancies reflecting their prevalence among Southern Chinese.

Molecular Characterization of Adult Tumors Diagnosed as Cerebellar Glioblastomas Identifies Subgroups Associated With Prognosis

Adult tumors diagnosed as cerebellar glioblastoma (cGBM) are rare and their optimal classification remains to be determined. The aim of this study was to identify subgroups of cGBM based on targeted molecular analysis. cGBM diagnosed between 2003 and 2017 were identified from the French Brain Tumor Database and reviewed according to the WHO 2021 classification. The following molecular alterations were studied: IDH1/2 , H3F3A , FGFR1 , BRAF , TERT promoter mutations, EGFR amplification, MGMT promoter methylation, and alternative lengthening of telomere status. DNA methylation profile was assessed in a subset of cases. Eighty-three cGBM were included and could be classified into 6 mutually exclusive subgroups associated with median age at diagnosis (MA) and prognosis: TERT -mutant and/or EGFR -amplified tumors (n=22, 26.5%, MA=62 y, median overall survival [OS]=4 mo), H3K27M-mutant tumors (n=15, 18.1%, MA=48 y, median OS=8 mo), mitogen-activated protein kinases (MAPK) pathway-activated tumors ( FGFR1 , BRAF mutation, or occurring in neurofibromatosis type I patients, n=15, 18.1%, MA=48 y, median OS=57 mo), radiation-associated tumors (n=5, 6%, MA=47 y, median OS=5 mo), IDH-mutant tumors (n=1), and unclassified tumors (n=25, 30.1%, MA=63 y, median OS=17 mo). Most MAPK pathway-activated tumors corresponded to high-grade astrocytomas with piloid features based on DNA methylation profiling. In multivariate analysis, MAPK pathway-activating alterations, ATRX loss of expression, and alternative lengthening of telomere positivity were independently associated with a better outcome and TERT / EGFR alterations with a worse outcome. cGBM display an important intertumoral heterogeneity. Targeted molecular analysis enables to classify the majority of tumors diagnosed as cGBM into mutually exclusive and clinically relevant subgroups. The presence of MAPK pathway alterations is associated with a much better prognosis.

OLIG2 expression level could be used as an independent prognostic factor for patients with cerebellar Glioblastoma (cGBM)

OBJECTIVES

The incidence of cerebellar Glioblastoma Multiforme (cGBM) is rare. Database like TCGA have not distinguish cGBM from GBM, our knowledge on cGBM gene expression characteristics is limited. The expression status of Oligodendrocyte Lineage Transcription factor 2 (OLIG2) and its clinical significance in cGBM is still unclear.

METHODS

The clinical data and tissue specimens of 73 cGBM patients were retrospectively studied. The association between OLIG2 expression level and the demographic characteristics of cGBM patients was identified by the Chi-Square test. The survival curves were drawn by Kaplan-Meier analysis. The independent prognostic factors was calculated according to Cox regression analysis.

RESULTS

The OLIG2 high expression was observed in about 57.5% (42/73) of the cGBM patients. Patients with high OLIG2 expression levels had a higher alive ratio at the end of follow-up (alive ratio: 70.6% vs. 29.4%, p = 0.04). The median survival time was 21 months and 13 months for high and low expression of OLIG2 (p < 0 .05). Univariate analysis and Multivariate analysis indicated that EOR (HR = 3.89, 95% CI 1.23‒12.26, p = 0.02), low OLIG2 expression (HR = 5.26, 95% CI 1.13‒24.59, p = 0.04), and without adjuvant therapy (HR = 4.95, 95% CI 1.22‒20.00, p = 0.03) were independent risk factors for the OS of cGBM patients.

CONCLUSION

High expression level of OLIG2 could be used as an independent favorable prognosis indicator in cGBM patients and be recognized as a characteristic biomarker of cGBM.

Cerebellar High-Grade Glioma: A Translationally Oriented Review of the Literature

World Health Organization (WHO) grade 4 gliomas of the cerebellum are rare entities whose understanding trails that of their supratentorial counterparts. Like supratentorial high-grade gliomas (sHGG), cerebellar high-grade gliomas (cHGG) preferentially affect males and prognosis is bleak; however, they are more common in a younger population. While current therapy for cerebellar and supratentorial HGG is the same, recent molecular analyses have identified features and subclasses of cerebellar tumors that may merit individualized targeting. One recent series of cHGG included the subclasses of (1) high-grade astrocytoma with piloid features (HGAP, ~31% of tumors); (2) H3K27M diffuse midline glioma (~8%); and (3) isocitrate dehydrogenase (IDH) wildtype glioblastoma (~43%). The latter had an unusually low-frequency of epidermal growth factor receptor (EGFR) and high-frequency of platelet-derived growth factor receptor alpha (PDGFRA) amplification, reflecting a different composition of methylation classes compared to supratentorial IDH-wildtype tumors. These new classifications have begun to reveal insights into the pathogenesis of HGG in the cerebellum and lead toward individualized treatment targeted toward the appropriate subclass of cHGG. Emerging therapeutic strategies include targeting the mitogen-activated protein kinases (MAPK) pathway and PDGFRA, oncolytic virotherapy, and immunotherapy. HGGs of the cerebellum exhibit biological differences compared to sHGG, and improved understanding of their molecular subclasses has the potential to advance treatment.

Unexpected Prolonged Survival in a Case of Cerebellar GBM: An Interesting Case with Literature Review

Glioblastoma multiforme (GBM) of cerebellar hemisphere is a rare entity and constitutes less than 1% of all the GBMs. The rarity of occurrence leads to significant challenge in differentiating morphologically from other subtypes of glioma in the posterior fossa. Previous studies have suggested that cerebellar GBM occurs in the younger age group as compared with the supratentorial counterpart.

Here, we report a case of cerebellar GBM in a young adult and discuss the pathogenesis including radiological and pathological aspects involved in the treatment of cerebellar GBM.

Differences in the MRI Signature and ADC Values of Diffuse Midline Gliomas with H3 K27M Mutation Compared to Midline Glioblastomas

We conducted a two-center retrospective survey on standard MRI features including apparent diffusion coefficient mapping (ADC) of diffuse midline gliomas H3 K27M-mutant (DMG) compared to midline glioblastomas H3 K27M-wildtype (midGBM-H3wt). We identified 39 intracranial DMG and 18 midGBM-H3wt tumors. Samples were microscopically re-evaluated for microvascular proliferations and necrosis. Image analysis focused on location, peritumoral edema, degree of contrast enhancement and DWI features. Within DMG, MRI features between tumors with or without histomorphological GBM features were compared. DMG occurred in 15/39 samples from the thalamus (38%), in 23/39 samples from the brainstem (59%) and in 1/39 tumors involving primarily the cerebellum (2%). Edema was present in 3/39 DMG cases (8%) versus 78% in the control (midGBM-H3wt) group (p < 0.001). Contrast enhancement at the tumor rim was detected in 17/39 DMG (44%) versus 67% in control (p = 0.155), and necrosis in 24/39 (62%) versus 89% in control (p = 0.060). Strong contrast enhancement was observed in 15/39 DMG (38%) versus 56% in control (p = 0.262). Apparent diffusion coefficient (ADC) histogram analysis showed significantly higher skewness and kurtosis values in the DMG group compared to the controls (p = 0.0016/p = 0.002). Minimum relative ADC (rADC) values, as well as the 10th and 25th rADC-percentiles, were lower in DMGs with GBM features within the DMG group (p < 0.001/p = 0.012/p = 0.027). In conclusion, DMG cases exhibited markedly less edema than midGBM-H3wt, even if histomorphological malignancy was present. Histologically malignant DMGs and midGBM-H3wt more often displayed strong enhancement, as well as rim enhancement, than DMGs without histomorphological malignancy. DMGs showed higher skewness and kurtosis values on ADC-histogram analysis compared to midGBM-H3wt. Lower minimum rADC values in DMGs indicated malignant histomorphological features, likely representing a more complex tissue microstructure.

Rapid Brainstem Infiltration of a Cerebellar Glioblastoma

A 79-year-old female complained of a one-month history of imbalance and headache. Brain MRI showed an irregular rim enhancing solid and cystic mass centered in the superomedial left cerebellar hemisphere. Resection of the lesion was recommended; however, the patient opted to undergo the procedure the following month because of the nearby Christmas holidays. When the patient returned 30 days later, a new brain MRI showed an enlargement of the cerebellar mass, extending to the brainstem and infiltrating the left brachium pontis, left posterior aspect of the tegmentum of the pons, and posterolateral medulla oblongata. Subtotal resection was performed without complications, and pathology was compatible with a primary cerebellar glioblastoma negative for IDH1/2 gene mutation. Because of the poor prognosis, the patient and her family members opted for hospice treatment, with the patient dying three weeks later. This case illustrates that cerebellar glioblastoma can rapidly infiltrate the brainstem.

Diffuse midline gliomas, H3 K27M-mutant are associated with less peritumoral edema and contrast enhancement in comparison to glioblastomas, H3 K27M-wildtype of midline structures

Purpose

The entity ‘diffuse midline glioma, H3 K27M-mutant (DMG)’ was introduced in the revised 4^th edition of the 2016 WHO classification of brain tumors. However, there are only a few reports on magnetic resonance imaging (MRI) of these tumors. Thus, we conducted a retrospective survey focused on MRI features of DMG compared to midline glioblastomas H3 K27M-wildtype (mGBM-H3wt).

Methods

We identified 24 DMG cases and 19 mGBM-H3wt patients as controls. After being retrospectively evaluated for microscopic evidence of microvascular proliferations (MVP) and tumor necrosis by two experienced neuropathologists to identify the defining histological criteria of mGBM-H3wt, the samples were further analyzed by two experienced readers regarding imaging features such as shape, peritumoral edema and contrast enhancement.

Results

The DMG were found in the thalamus in 37.5% of cases (controls 63%), in the brainstem in 50% (vs. 32%) and spinal cord in 12.5% (vs. 5%). In MRI and considering MVP, DMG were found to be by far less likely to develop peritumoral edema (OR: 0.13; 95%-CL: 0.02–0.62) (p = 0.010). They, similarly, were associated with a significantly lower probability of developing strong contrast enhancement compared to mGBM-H3wt (OR: 0.10; 95%-CL: 0.02–0.47) (P = 0.003).

Conclusion

Despite having highly variable imaging features, DMG exhibited markedly less edema and lower contrast enhancement in MRI compared to mGBM-H3wt. Of these features, the enhancement level was associated with evidence of MVP.

Cerebellar anaplastic astrocytoma in adult patients: 15 consecutive cases from a single institution and literature review

Adult cerebellar anaplastic astrocytomas (cAA) are rare entities and their clinical and genetic appearances are still ill defined. Previously, malignant gliomas of the cerebellum were combined and reviewed together (cAA and cerebellar glioblastomas (cGB), that could have possibly affected overall survival (OS) and progression-free survival (PFS). We present characteristics of 15 adult patients with cAA and compared them to a series of 45 patients with a supratentorial AA (sAA) in order to elicit the effect of tumor location on OS and PFS. The mean age at cAA diagnosis was 39.3 years (range 19-72). A history of neurofibromatosis type I was noted in 1 patient (6.7%). An IDH-1 mutation was identified in 6/15 cases and a methylated MGMT promoter in 5/15 cases. Patients in study and control groups were matched in age, sex and IDH-1 mutation status. Patients in a study group tended to present with longer overall survival (50 vs. 36.5 months), but the difference did not reach statistical significance. In both cAA and supratentorial AA groups presence of the IDH-1 mutation remains a positive predictor for the prolonged survival. The present study suggests that adult cAA constitute a group of gliomas with relatively higher rate of IDH-1 mutations and prognosis similar to supratentorial AA. The present study is the first to systematically compare cAA and supratentorial AA with respect to their genetic characteristics and suggests that both groups show a similar survival prognosis.

The prognostic significance of clinicopathological features in meningiomas: Microscopic brain invasion can predict patient outcome in otherwise benign meningiomas

AIMS

Brain invasion (BI) was firstly defined as a single criterion of atypia in otherwise benign meningiomas in the revised fourth edition of 2016 WHO classification of brain tumours after being previously inconsistently addressed. However, recent studies have raised doubts about the prognostic significance of BI in otherwise benign meningiomas. In our study, we investigate the reproducibility of such a prognostic effect.

METHODS

We identified two cohorts one consisting of 483 patients with meningioma WHO grade I (M°I) or atypical meningioma WHO grade II (M°II) from Hannover Medical School and the other including atypical meningiomas defined according to the classical WHO criteria (M°IIb) from the University Hospital Heidelberg. Follow-up data with a median observation time of 38.2 months were available from 308 cases. These included 243 M°I and 65 M°II patients with the latter group consisting of 25 patients with otherwise benign meningiomas with BI (M°IIa) and 40 with M°IIb.

RESULTS

A significant difference of progression-free interval (PFI) was found between patients with M°I and M°II, M°I and M°IIa and those with M°I and M°IIb of both cohorts and each separately. However, PFI of M°IIa and M°IIb patients showed no significant difference. In the multivariate regression analysis adjusted for M°I/M°IIa versus M°IIb, sex, age, extent of resection and tumour location, BI exhibited the strongest risk of relapse (Hazard ratio: 4.95) serving as an independent predictor of PFI (p = 0.002).

CONCLUSIONS

Our results clearly support the definition of BI as a single criterion of atypia in WHO classification of 2016.

Management, functional outcomes and survival in a French multicentric series of 118 adult patients with cerebellar glioblastoma

PURPOSE

To analyze the outcomes and predictors in a large series of cerebellar glioblastomas in order to guide patient management.

METHODS

The French brain tumor database and the Club de Neuro-Oncologie of the Société Française de Neurochirurgie retrospectively identified adult patients with cerebellar glioblastoma diagnosed between 2003 and 2017. Diagnosis was confirmed by a centralized neuropathological review.

RESULTS

Data from 118 cerebellar glioblastoma patients were analyzed (mean age 55.9 years, 55.1% males). The clinical presentation associated raised intracranial pressure (50.8%), static cerebellar syndrome (68.6%), kinetic cerebellar syndrome (49.2%) and/or cranial nerve disorders (17.8%). Glioblastomas were hemispheric (55.9%), vermian (14.4%) or both (29.7%). Hydrocephalus was present in 49 patients (41.5%). Histologically, tumors corresponded either to IDH-wild-type or to K27-mutant glioblastomas. Surgery consisted of total (12.7%), subtotal (35.6%), partial resection (33.9%) or biopsy (17.8%). The postoperative Karnofsky performance status was improved, stable and worsened in 22.4%, 43.9% and 33.7% of patients, respectively. Progression-free and overall survivals reached 5.1 months and 9.1 months, respectively. Compared to other surgical strategies, total or subtotal resection improved the Karnofsky performance status (33.3% vs 12.5%, p < 0.001), prolonged progression-free and overall survivals (6.5 vs 4.3 months, p = 0.015 and 16.7 vs 6.2 months, p < 0.001, respectively) and had a comparable complication rate (40.4% vs 31.1%, p = 0.29). After total or subtotal resection, the functional outcomes were correlated with age (p = 0.004) and cerebellar hemispheric tumor location (p < 0.001) but not brainstem infiltration (p = 0.16).

CONCLUSION

In selected patients, maximal resection of cerebellar glioblastoma is associated with improved onco-functional outcomes, compared with less invasive procedures.

Treatment patterns and outcomes for cerebellar glioblastoma in the concomitant chemoradiation era: A National Cancer database study

Cerebellar glioblastoma (GB) is much rarer than its supratentorial counterpart, and potentially of different molecular origin. Prior database studies are of limited size and reported on patients who preceded the validation of temozolomide. Thus, we provide an updated population-based analysis of the treatment trends and outcomes since the standardization of GB adjuvant chemoradiation. Patients diagnosed with primary cerebellar and supratentorial GB were identified from the National Cancer Database spanning 2005-2015. Patients were characterized by demographics, extent of resection, and adjuvant chemotherapy or radiation status. Cohorts were primarily and secondarily assessed for overall survival by tumor site and treatment history, respectively. A total of 655 patients with cerebellar GB were identified (0.6%). Cerebellar GB patients, compared to supratentorial GB were more likely to undergo a biopsy or subtotal resection (13.4% vs 9.3% and 16.0% vs 13.4%, p-value < 0.001), and less likely to pursue adjuvant therapy (48.4% vs 52.7%, p-value < 0.001). Overall median survivals were 9.3 and 9.4 months, respectively. On multivariable analysis, gross total resection, radiation, and chemotherapy were found to be predictors of improved overall survival (HR 0.77, p = 0.038; HR 0.67, p < 0.001; and HR = 0.77, p = 0.030, respectively). While many management principles are currently shared between cerebellar and supratentorial GB, aggressive regimens appear less frequently prescribed. Survival continues to match supratentorial outcomes and may benefit from future, systemic guidance by distinguishing molecular features.

Infratentorial IDH-mutant astrocytoma is a distinct subtype

Diffuse IDH-mutant astrocytic tumors are rarely diagnosed in the cerebellum or brainstem. In this multi-institutional study, we characterized a series of primary infratentorial IDH-mutant astrocytic tumors with respect to clinical and molecular parameters. We report that about 80% of IDH mutations in these tumors are of non-IDH1-R132H variants which are rare in supratentorial astrocytomas. Most frequently, IDH1-R132C/G and IDH2-R172S/G mutations were present. Moreover, the frequencies of ATRX-loss and MGMT promoter methylation, which are typically associated with IDH mutations in supratentorial astrocytic tumors, were significantly lower in the infratentorial compartment. Gene panel sequencing revealed two samples with IDH1-R132C/H3F3A-K27M co-mutations. Genome-wide DNA methylation as well as chromosomal copy number profiling provided further evidence for a molecular distinctiveness of infratentorial IDH-mutant astrocytomas. Clinical outcome of patients with infratentorial IDH-mutant astrocytomas is significantly better than that of patients with diffuse midline gliomas, H3K27M-mutant (p < 0.005) and significantly worse than that of patients with supratentorial IDH-mutant astrocytomas (p = 0.028). The presented data highlight the very existence and distinctiveness of infratentorial IDH-mutant astrocytomas that have important implications for diagnostics and prognostication. They imply that molecular testing is critical for detection of these tumors, since many of these tumors cannot be identified by immunohistochemistry applied for the mutated IDH1-R132H protein or loss of ATRX.

A Rare Case of Cerebellar Glioblastoma Mimicking Acute Stroke in an Elderly Patient

Patient: Female, 82-year-old

Final Diagnosis: Cerebellar glioblastoma

Symptoms: Dizziness

Medication: —

Clinical Procedure: —

Specialty: Neurology

Primary cerebellar glioblastomas in children: clinical presentation and management

Pediatric cerebellar glioblastomas (pcGBMs) are rare and their characteristics remain ill-defined. We conducted a retrospective analysis of pediatric cerebellar glioblastomas who underwent surgery from 2008 to 2019 in our department. Besides, we performed a literature review of the literature data on pcGBMs. Ten children with mean age of 9.4 years were included. During the follow-up, six patients died with mean survival time of 11.7 months, four patients survived with mean follow-up of 28 months. Seven patients underwent molecular analysis, no patients detected IDH1 mutations, four patients (57.1%) had H3K27M mutations, and two patients (28.6%) had MGMT promoter methylation. The literature review identified 38 pcGBMs cases (including ours), with mean age of 8.84 ± 4.20 years (range, 1-16 years). Increased ICP was the commonest sign. Eighteen (47.4%) patients underwent GTR and fifteen (45.5%) patients received STR. Postoperative radiation (RT) was conducted in 28 patients (75.7%) and 23 patients (65.7%) received chemotherapy. During the follow-up, 25 patients died with mean survival time of 12.21 months and 11 patients survived with average follow-up of 29.3 months. Kaplan-Meier survival depicted chemotherapy (P < 0.001) or radiation (P < 0.001) had positive impact on overall survival. Multivariate analysis revealed chemotherapy was a significant predictor of survival with a hazard ratio of 3.264 (P = 0.038). Our study found mean overall survival time for pcGBMs patients was 12.21 months. PcGBMs may have distinct molecular features, with higher incidence of H3K27M mutation and were always IDH1 wild-type. We recommend the routine postoperative radiotherapy and chemotherapy in pcGBMs.

Gliomatosis cerebri (GC) or GC-like? A picture to be reconsidered in neuro-oncology based on large retrospective analysis of GC series

INTRODUCTION

Gliomatosis cerebri (GC), defined until 2016 as a distinct astrocytic glioma entity, has been removed from the 2016 World Health Organization classification of tumors of the central nervous system. However, its identity is still debated.

MATERIALS AND METHODS

We retrospectively present 122 patients, including a subgroup with histology confirmation (n = 75, cohort b).

RESULTS

Radiological features showed extension limited to 3 lobes in 31%; bilateral, midline, and basal ganglia and subtentorial involvement in 95%, 52%, 84%, and 60%, respectively; and contrast enhancement in 59.5%. Perioperative mortality occurred in 4%. Histology concluded for grades II, III, and IV, respectively, in 31%, 35%, and 22% (not specified in 12%). Thirty-one percent had isocitrate dehydrogenase (IDH) 1 mutation. Treatments included radiotherapy in 51.2% and chemotherapy in 74.5%. Median overall survival was 17 months. Negative prognostic factors for survival were older age, poorer Karnofsky Performance Scale (KPS), subtentorial, midline and disseminated disease, and lack of chemotherapy, at univariate analysis. At multivariate analysis, KPS ≥ 80, chemotherapy, and subtentorial and disseminated disease remained prognostic (p < 0.0001). For cohort b, same prognostic factors were confirmed, except for midline location, at univariate analysis; at multivariate analysis, only KPS ≥ 80 and chemotherapy remained prognostic (p < 0.0001).

CONCLUSION

We described clinical, neuroimaging, management, and histomolecular features of one of the largest GC series. We identified KPS ≥ 80, radiological pattern as subtentorial localization and dissemination, and chemotherapy as prognostic factors, at multivariate analysis. Planning prospective study, associated to focused genetic assays, could help to clarify if GC has specific features that may result in the identification as a separate entity from other gliomas.

Tumors diagnosed as cerebellar glioblastoma comprise distinct molecular entities

In this multi-institutional study we compiled a retrospective cohort of 86 posterior fossa tumors having received the diagnosis of cerebellar glioblastoma (cGBM). All tumors were reviewed histologically and subjected to array-based methylation analysis followed by algorithm-based classification into distinct methylation classes (MCs). The single MC containing the largest proportion of 25 tumors diagnosed as cGBM was MC anaplastic astrocytoma with piloid features representing a recently-described molecular tumor entity not yet included in the WHO Classification of Tumours of the Central Nervous System (WHO classification). Twenty-nine tumors molecularly corresponded to either of 6 methylation subclasses subsumed in the MC family GBM IDH wildtype. Further we identified 6 tumors belonging to the MC diffuse midline glioma H3 K27 M mutant and 6 tumors allotted to the MC IDH mutant glioma subclass astrocytoma. Two tumors were classified as MC pilocytic astrocytoma of the posterior fossa, one as MC CNS high grade neuroepithelial tumor with BCOR alteration and one as MC control tissue, inflammatory tumor microenvironment. The methylation profiles of 16 tumors could not clearly be assigned to one distinct MC. In comparison to supratentorial localization, the MC GBM IDH wildtype subclass midline was overrepresented, whereas the MCs GBM IDH wildtype subclass mesenchymal and subclass RTK II were underrepresented in the cerebellum. Based on the integration of molecular and histological findings all tumors received an integrated diagnosis in line with the WHO classification 2016. In conclusion, cGBM does not represent a molecularly uniform tumor entity, but rather comprises different brain tumor entities with diverse prognosis and therapeutic options. Distinction of these molecular tumor classes requires molecular analysis. More than 30% of tumors diagnosed as cGBM belong to the recently described molecular entity of anaplastic astrocytoma with piloid features.