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Diffuse gliomas in adults encompass a heterogenous group of central nervous system neoplasms. In recent years, extensive (epi-)genomic profiling has identified several glioma subgroups characterized by distinct molecular characteristics, most importantly IDH1/2 and histone H3 mutations. A group of 16 diffuse gliomas classified as "adult-type diffuse high-grade glioma, IDH-wildtype, subtype F (HGG-F)" was identified by the DKFZ v12.5 Brain Tumor Classifier . Histopathologic characterization, exome sequencing, and review of clinical data was performed in all cases. Based on unsupervised t -distributed stochastic neighbor embedding and clustering analysis of genome-wide DNA methylation data, HGG-F shows distinct epigenetic profiles separate from established central nervous system tumors. Exome sequencing demonstrated frequent TERT promoter (12/15 cases), PIK3R1 (11/16), and TP53 mutations (5/16). Radiologic characteristics were reminiscent of gliomatosis cerebri in 9/14 cases (64%). Histopathologically, most cases were classified as diffuse gliomas (7/16, 44%) or were suspicious for the infiltration zone of a diffuse glioma (5/16, 31%). None of the cases demonstrated microvascular proliferation or necrosis. Outcome of 14 patients with follow-up data was better compared to IDH-wildtype glioblastomas with a median progression-free survival of 58 months and overall survival of 74 months (both P <0.0001). Our series represents a novel type of adult-type diffuse glioma with distinct molecular and clinical features. Importantly, we provide evidence that TERT promoter mutations in diffuse gliomas without further morphologic or molecular signs of high-grade glioma should be interpreted in the context of the clinicoradiologic presentation as well as epigenetic profile and may not be suitable as a standalone marker for glioblastoma, IDH-wildtype., Competing Interests: Conflicts of Interest and Source of Funding: Supported by a Deutsches Konsortium für Translationale Krebsforschung (DKTK) Young Investigator grant to L.S. The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Background: A methylation-based classification of ependymoma has recently found broad application. However, the diagnostic advantage and implications for treatment decisions remain unclear. Here, we retrospectively evaluate the impact of surgery and radiotherapy on outcome after molecular reclassification of adult intracranial ependymomas., Methods: Tumors diagnosed as intracranial ependymomas from 170 adult patients collected from 8 diagnostic institutions were subjected to DNA methylation profiling. Molecular classes, patient characteristics, and treatment were correlated with progression-free survival (PFS)., Results: The classifier indicated an ependymal tumor in 73.5%, a different tumor entity in 10.6%, and non-classifiable tumors in 15.9% of cases, respectively. The most prevalent molecular classes were posterior fossa ependymoma group B (EPN-PFB, 32.9%), posterior fossa subependymoma (PF-SE, 25.9%), and supratentorial ZFTA fusion-positive ependymoma (EPN-ZFTA, 11.2%). With a median follow-up of 60.0 months, the 5- and 10-year-PFS rates were 64.5% and 41.8% for EPN-PFB, 67.4% and 45.2% for PF-SE, and 60.3% and 60.3% for EPN-ZFTA. In EPN-PFB, but not in other molecular classes, gross total resection (GTR) (P = .009) and postoperative radiotherapy (P = .007) were significantly associated with improved PFS in multivariable analysis. Histological tumor grading (WHO 2 vs. 3) was not a predictor of the prognosis within molecularly defined ependymoma classes., Conclusions: DNA methylation profiling improves diagnostic accuracy and risk stratification in adult intracranial ependymoma. The molecular class of PF-SE is unexpectedly prevalent among adult tumors with ependymoma histology and relapsed as frequently as EPN-PFB, despite the supposed benign nature. GTR and radiotherapy may represent key factors in determining the outcome of EPN-PFB patients., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Atypical teratoid/rhabdoid tumor (AT/RT) is a malignant central nervous system tumor predominantly affecting infants. Mutations of SMARCB1 or (rarely) SMARCA4 causing loss of nuclear SMARCB1 or SMARCA4 protein expression are characteristic features, but further recurrent genetic alterations are lacking. Most AT/RTs occur de novo, but secondary AT/RTs arising from other central nervous system tumors have been reported. Malignant gliomas, IDH wild-type, arising in patients with Li-Fraumeni syndrome typically show somatic mutations of TP53 as well as complex copy number alterations, but little is known about the loss of SMARCB1 or SMARCA4 protein expression in this context. Here, we report 2 children in whom malignant supratentorial brain tumors with SMARCB1 deficiency, complex copy number alterations, and somatic TP53 mutations lead to the discovery of pathogenic/likely pathogenic TP53 variants in the germline. Screening of the molecularneuropathology.org dataset for cases with similar genetic and epigenetic alterations yielded another case with SMARCA4 deficiency in a young adult with Li-Fraumeni syndrome. In conclusion, SMARCB1-deficient or SMARCA4-deficient malignant brain tumors with complex copy number alterations and somatic TP53 mutations in children and young adults may represent the first clinical manifestation of Li-Fraumeni syndrome and should prompt genetic counseling and investigation for TP53 germline status., Competing Interests: Conflicts of Interest and Source of Funding: Supported by IZKF Münster (Ha3/017/20). C.P.K. has been supported by the Deutsche Kinderkrebsstiftung (DKS2019.13) and BMBF ADDRess (01GM1909A). B.B. is supported by the Deutsche Kinderkrebsstiftung (DKS 2020.05). M.C.F. and R.S. are supported Deutsche Krebshilfe (DKH 70113981, 70114040). The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Pleomorphic xanthoastrocytoma (PXA) in its classic manifestation exhibits distinct morphological features and is assigned to CNS WHO grade 2 or grade 3. Distinction from glioblastoma variants and lower grade glial and glioneuronal tumors is a common diagnostic challenge. We compared a morphologically defined set of PXA (histPXA) with an independent set, defined by DNA methylation analysis (mcPXA). HistPXA encompassed 144 tumors all subjected to DNA methylation array analysis. Sixty-two histPXA matched to the methylation class mcPXA. These were combined with the cases that showed the mcPXA signature but had received a histopathological diagnosis other than PXA. This cohort constituted a set of 220 mcPXA. Molecular and clinical parameters were analyzed in these groups. Morphological parameters were analyzed in a subset of tumors with FFPE tissue available. HistPXA revealed considerable heterogeneity in regard to methylation classes, with methylation classes glioblastoma and ganglioglioma being the most frequent mismatches. Similarly, the mcPXA cohort contained tumors of diverse histological diagnoses, with glioblastoma constituting the most frequent mismatch. Subsequent analyses demonstrated the presence of canonical pTERT mutations to be associated with unfavorable prognosis among mcPXA. Based on these data, we consider the tumor type PXA to be histologically more varied than previously assumed. Histological approach to diagnosis will predominantly identify cases with the established archetypical morphology. DNA methylation analysis includes additional tumors in the tumor class PXA that share similar DNA methylation profile but lack the typical morphology of a PXA. DNA methylation analysis also assist in separating other tumor types with morphologic overlap to PXA. Our data suggest the presence of canonical pTERT mutations as a robust indicator for poor prognosis in methylation class PXA., (© 2022. The Author(s).)

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly malignant central nervous system tumor predominantly occurring in infants that may also arise in older children and adults. Rare secondary AT/RT developing from other tumors such as pleomorphic xanthoastrocytoma (PXA) are on record, but AT/RT presenting with molecular features of PXA have not been described. Here, we report 3 malignant central nervous system tumors in children (10, 13, and 18 y old). All tumors were located in the temporal lobe. In 2 cases, there was no history of a low-grade precursor lesion; in 1 case anaplastic PXA had been diagnosed 3 months earlier. Histopathologically, all tumors were composed of RT cells and showed frank signs of malignancy as well as loss of nuclear SMARCB1/INI1 protein expression. Two cases displayed homozygous deletions of the SMARCB1 region while the third case showed an exon 7 mutation (c.849&#95;850delGT; p.Met283Ilefs*77). Of note, DNA methylation profiles did not group with AT/RT or other tumor entities using the Heidelberg Brain Tumor Classifier (version v11b4). By unsupervised t-distributed stochastic neighbor embedding analysis and hierarchical clustering analysis, however, all tumors clearly grouped with PXA. Genome-wide copy number analysis revealed homozygous CDNK2A/B deletions and gains of whole chromosome 7. BRAF V600E mutations could be demonstrated in all cases. In conclusion, the possibility of AT/RT with molecular features of PXA needs to be taken into account and warrants molecular characterization of AT/RT especially in older children. Since treatments targeting mutated BRAF are available, identification of such cases may also have therapeutic consequences., Competing Interests: Conflicts of Interest and Source of Funding: M.H. and C.T. are supported by Deutsche Forschungsgemeinschaft (HA 3060/8-1 and TH 2345/1-1). The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Risk factors for prediction of prognosis in meningiomas derivable from routine preoperative magnetic resonance imaging (pMRI) remain elusive. Correlations of tumor and edema volume, disruption of the arachnoid layer, heterogeneity of contrast enhancement, enhancement of the capsule, T2-intensity, tumor shape, and calcifications on pMRI with tumor recurrence and high-grade (WHO grade II/III) histology were analyzed in 565 patients who underwent surgery for WHO grade I (N = 516, 91%) or II/III (high-grade histology, N = 49, 9%) meningioma between 1991 and 2018. Edema volume (OR, 1.00; p = 0.003), heterogeneous contrast enhancement (OR, 3.10; p < 0.001), and an irregular shape (OR, 2.16; p = 0.015) were associated with high-grade histology. Multivariate analyses confirmed edema volume (OR, 1.00; p = 0.037) and heterogeneous contrast enhancement (OR, 2.51; p = 0.014) as risk factors for high-grade histology. Tumor volume (HR, 1.01; p = 0.045), disruption of the arachnoid layer (HR, 2.50; p = 0.003), heterogeneous contrast enhancement (HR, 2.05; p = 0.007), and an irregular tumor shape (HR, 2.57; p = 0.001) were correlated with recurrence. Multivariate analyses confirmed tumor volume (HR, 1.01; p = 0.032) and disruption of the arachnoid layer (HR, 2.44; p = 0.013) as risk factors for recurrence, independent of histology. Subgroup analyses revealed disruption of the arachnoid layer (HR, 9.41; p < 0.001) as a stronger risk factor for recurrence than high-grade histology (HR, 5.15; p = 0.001). Routine pMRI contains relevant information about the risk of recurrence or high-grade histology of meningioma patients. Loss of integrity of the arachnoid layer on MRI had a higher prognostic value than the WHO grading, and underlying histological or molecular alterations remain to be determined.

Atypical teratoid/rhabdoid tumor (ATRT) is a highly malignant brain tumor predominantly occurring in infants. Mutations of the SMARCB1 gene are the characteristic genetic lesion. SMARCB1-mutant tumors in adolescents and adults are rare and may show uncommon histopathological and clinical features. Here we report seven SMARCB1-deficient intracranial tumors sharing distinct clinical, histopathological and molecular features. Median age of the four females and three males was 40 years (range 15-61 years). All tumors were located in the pineal region. Histopathologically, these tumors displayed spindled and epithelioid cells embedded in a desmoplastic stroma alternating with a variable extent of a loose myxoid matrix. All cases showed loss of nuclear SMARCB1/INI1 protein expression, expression of EMA and CD34 was frequent and the Ki67/MIB1 proliferation index was low in the majority of cases (median 3%). Three cases displayed heterozygous SMARCB1 deletions and two cases a homozygous SMARCB1 deletion. On sequencing, one tumor showed a 2 bp deletion in exon 4 (c.369&#95;370del) and one a short duplication in exon 3 (c.237&#95;276dup) both resulting in frameshift mutations. Most DNA methylation profiles were not classifiable using the Heidelberg Brain Tumor Classifier (version v11b4). By unsupervised t-SNE analysis and hierarchical clustering analysis, however, all tumors grouped closely together and showed similarities with ATRT-MYC. After a median observation period of 48 months, three patients were alive with stable disease, whereas one patient experienced tumor progression and three patients had succumbed to disease. In conclusion, our series represents an entity with distinct clinical, histopathological and molecular features showing epigenetic similarities with ATRT-MYC. We propose the designation desmoplastic myxoid tumor (DMT), SMARCB1-mutant, for these tumors.

Papillary glioneuronal tumor (PGNT) is a WHO-defined brain tumor entity that poses a major diagnostic challenge. Recently, SLC44A1-PRKCA fusions have been described in PGNT. We subjected 28 brain tumors from different institutions histologically diagnosed as PGNT to molecular and morphological analysis. Array-based methylation analysis revealed that 17/28 tumors exhibited methylation profiles typical for other tumor entities, mostly dysembryoplastic neuroepithelial tumor and hemispheric pilocytic astrocytoma. Conversely, 11/28 tumors exhibited a unique profile, thus constituting a distinct methylation class PGNT. By screening the extended Heidelberg cohort containing over 25,000 CNS tumors, we identified three additional tumors belonging to this methylation cluster but originally histologically diagnosed otherwise. RNA sequencing for the detection of SLC44A1-PRKCA fusions could be performed on 19 of the tumors, 10 of them belonging to the methylation class PGNT. In two additional cases, SLC44A1-PRKCA fusions were confirmed by FISH. We detected fusions involving PRKCA in all cases of this methylation class with material available for analyses: the canonical SLC44A1-PRKCA fusion was observed in 11/12 tumors, while the remaining case exhibited a NOTCH1-PRKCA fusion. Neither of the fusions was found in the tumors belonging to other methylation classes. Our results point towards a high misclassification rate of the morphological diagnosis PGNT and clearly demonstrate the necessity of molecular analyses. PRKCA fusions are highly diagnostic for PGNT, and detection by RNA sequencing enables the identification of rare fusion partners. Methylation analysis recognizes a unique methylation class PGNT irrespective of the nature of the PRKCA fusion.

Objective: Identification of risk factors for perioperative epilepsy remains crucial in the care of patients with meningioma. Moreover, associations of brain invasion with clinical and radiological variables have been largely unexplored. The authors hypothesized that invasion of the cortex and subsequent increased edema facilitate seizures, and they compared radiological data and perioperative seizures in patients with brain-invasive or noninvasive meningioma., Methods: Correlations of brain invasion with tumor and edema volumes and preoperative and postoperative seizures were analyzed in univariate and multivariate analyses., Results: Totals of 108 (61%) females and 68 (39%) males with a median age of 60 years and harboring totals of 92 (52%) grade I, 79 (45%) grade II, and 5 (3%) grade III tumors were included. Brain invasion was found in 38 (22%) patients and was absent in 138 (78%) patients. The tumors were located at the convexity in 72 (41%) patients, at the falx cerebri in 26 (15%), at the skull base in 69 (39%), in the posterior fossa in 7 (4%), and in the ventricle in 2 (1%); the median tumor and edema volumes were 13.73 cm3 (range 0.81-162.22 cm3) and 1.38 cm3 (range 0.00-355.80 cm3), respectively. As expected, edema volume increased with rising tumor volume (p < 0.001). Brain invasion was independent of tumor volume (p = 0.176) but strongly correlated with edema volume (p < 0.001). The mean edema volume in noninvasive tumors was 33.0 cm3, but in invasive tumors, it was 130.7 cm3 (p = 0.008). The frequency of preoperative seizures was independent of the patients' age, sex, and tumor location; however, the frequency was 32% (n = 12) in patients with invasive meningioma and 15% (n = 21) in those with noninvasive meningioma (p = 0.033). In contrast, the probability of detecting brain invasion microscopically was increased more than 2-fold in patients with a history of preoperative seizures (OR 2.57, 95% CI 1.13-5.88; p = 0.025). In univariate analyses, the rate of preoperative seizures correlated slightly with tumor volume (p = 0.049) but strongly with edema volume (p = 0.014), whereas seizure semiology was found to be independent of brain invasion (p = 0.211). In multivariate analyses adjusted for age, sex, tumor location, tumor and edema volumes, and WHO grade, rising tumor volume (OR 1.02, 95% CI 1.00-1.03; p = 0.042) and especially brain invasion (OR 5.26, 95% CI 1.52-18.15; p = 0.009) were identified as independent predictors of preoperative seizures. Nine (5%) patients developed new seizures within a median follow-up time of 15 months after surgery. Development of postoperative epilepsy was independent of all clinical variables, including Simpson grade (p = 0.133), tumor location (p = 0.936), brain invasion (p = 0.408), and preoperative edema volume (p = 0.081), but was correlated with increasing preoperative tumor volume (p = 0.004). Postoperative seizure-free rates were similar among patients with invasive and those with noninvasive meningioma (p = 0.372)., Conclusions: Brain invasion was identified as a new and strong predictor for preoperative, but not postoperative, seizures. Although also associated with increased peritumoral edema, seizures in patients with invasive meningioma might be facilitated substantially by cortical invasion itself. Consideration of seizures in consultations between the neurosurgeon and neuropathologist can improve the microscopic detection of brain invasion.

Fluorescence-guided surgery (FGS) has been established as a powerful technique for glioblastoma resection. After oral application of the prodrug 5-aminolevulinic acid (5-ALA), protoporphyrin IX (PpIX) is formed as an intermediate of the heme-biosynthesis cascade and accumulates within the tumor. By intraoperative fluorescence microscopy, the specific PpIX fluorescence can be used to differentiate the tumor from healthy brain tissue. To investigate possible limitations of fluorescence diagnosis, the complementary use of molecular and elemental mass-spectrometry imaging (MSI) is presented. Matrix-assisted laser-desorption-ionization mass spectrometry (MALDI-MS) is used to examine the distribution of PpIX and heme b in human brain tumors. MALDI-MS/MS imaging is performed to validate MS data and improve the signal-to-noise ratio (S/N). Comparing the imaging results with histological evaluation, increased PpIX accumulation in areas of high tumor-cell density is observed. Heme b accumulation are only found in areas of blood vessels and hemorrhage, confirming the hampered transformation from PpIX to heme b in glioblastoma tissue. Investigation of non-neoplastic brain tissue and glioblastoma resected without external 5-ALA administration as control samples with true-negative fluorescence verified the absence of PpIX accumulation. Analysis of necrotic tumor tissue and gliosarcoma, one rare type of glioma appearing nonfluorescent during FGS, as case examples with false-negative-fluorescence diagnosis, revealed the absence of significant amounts of PpIX, indicating an impairment of PpIX formation. Molecular analysis is complemented by quantitative laser ablation-inductively coupled plasma (LA-ICP) MSI correlating heme b and Fe distribution. Mathematical pixel-by-pixel correlation of molecular and elemental data revealed a positive correlation with heteroscedasticity for the spatially resolved heme b signal intensities and Fe concentrations.

Tumors with histological features of pilocytic astrocytoma (PA), but with increased mitotic activity and additional high-grade features (particularly microvascular proliferation and palisading necrosis) have often been designated anaplastic pilocytic astrocytomas. The status of these tumors as a separate entity has not yet been conclusively demonstrated and molecular features have only been partially characterized. We performed DNA methylation profiling of 102 histologically defined anaplastic pilocytic astrocytomas. T-distributed stochastic neighbor-embedding (t-SNE) and hierarchical clustering analysis of these 102 cases against 158 reference cases from 12 glioma reference classes revealed that a subset of 83 of these tumors share a common DNA methylation profile that is distinct from the reference classes. These 83 tumors were thus denominated DNA methylation class anaplastic astrocytoma with piloid features (MC AAP). The 19 remaining tumors were distributed amongst the reference classes, with additional testing confirming the molecular diagnosis in most cases. Median age of patients with MC AAP was 41.5 years. The most frequent localization was the posterior fossa (74%). Deletions of CDKN2A/B (66/83, 80%), MAPK pathway gene alterations (49/65, 75%, most frequently affecting NF1, followed by BRAF and FGFR1) and mutations of ATRX or loss of ATRX expression (33/74, 45%) were the most common molecular alterations. All tumors were IDH1/2 wildtype. The MGMT promoter was methylated in 38/83 tumors (45%). Outcome analysis confirmed an unfavorable clinical course in comparison to PA, but better than IDH wildtype glioblastoma. In conclusion, we show that a subset of histologically defined anaplastic pilocytic astrocytomas forms a separate DNA methylation cluster, harbors recurrent alterations in MAPK pathway genes in combination with alterations of CDKN2A/B and ATRX, affects patients who are on average older than those diagnosed with PA and has an intermediate clinical outcome.

The histological and molecular features and even the mere existence of diffuse astrocytoma, IDH-wildtype, remain unclear. We therefore examined 212 diffuse astrocytomas (grade II WHO) in adults using IDH1(R132H) immunohistochemistry followed by IDH1/IDH2 sequencing and neuroimaging review. DNA methylation status and copy number profiles were assessed by Infinium HumanMethylation450k BeadChip. Only 25/212 patients harbored tumors without IDH1/IDH2 hotspot mutations and without contrast enhancement. By DNA methylation profiling, 10/25 tumors were classified as glioblastoma, IDH-wildtype, and an additional 7 cases could not be classified using methylome analysis, but showed genetic characteristics of glioblastoma. Histologically, all of these 17 tumors were low-grade diffuse astrocytomas. Nevertheless, 10/17 patients experienced early malignant progression. Other methylation classes included diffuse midline glioma, H3 K27M-mutant, diffuse astrocytoma, IDH-mutant, pilocytic astrocytoma, and normal or reactive brain tissue (total n = 8). In conclusion, no convincing diffuse astrocytoma, IDH-wildtype, was identified. Most IDH-wildtype tumors showing histopathological and radiological features of low-grade diffuse astrocytoma exhibit molecular and clinical features of high-grade glioma and may represent an early stage of primary glioblastoma. Our findings have implications for the biology, classification and neuropathological diagnosis of diffuse astrocytoma, IDH-wildtype in adults.

Rhabdoid phenotype and loss of SMARCB1 expression in a brain tumor are characteristic features of atypical teratoid/rhabdoid tumors (ATRT). Rare non-rhabdoid brain tumors showing cribriform growth pattern and SMARCB1 loss have been designated cribriform neuroepithelial tumor (CRINET). Small case series suggest that CRINETs may have a relatively favorable prognosis. However, the long-term outcome is unclear and it remains uncertain whether CRINET represents a distinct entity or a variant of ATRT. Therefore, 10 CRINETs were clinically and molecularly characterized and compared with 10 ATRTs of each of three recently described molecular subgroups (i.e. ATRT-TYR, ATRT-SHH and ATRT-MYC) using Illumina Infinium HumanMethylation450 arrays, FISH, MLPA, and sequencing. Furthermore, outcome was compared to a larger cohort of 27 children with ATRT-TYR. Median age of the 6 boys and 4 girls harboring a CRINET was 20 months. On histopathological examination, all CRINETs demonstrated a cribriform growth pattern and distinct tyrosinase staining. On unsupervised cluster analysis of methylation data, all CRINETs examined exclusively clustered within the ATRT-TYR molecular subgroup. As ATRT-TYR, CRINETs mainly showed large heterozygous 22q deletions (9/10) and SMARCB1 mutations of the other allele. In two patients, SMARCB1 mutations were also present in the germline. Estimated mean overall survival in patients with CRINETs was 125 months (95% confidence interval 100-151 months) as compared to only 53 (33-74) months in patients with ATRTs of the ATRT-TYR subgroup (Log-Rank P < 0.05). In conclusion, CRINET represents a SMARCB1-deficient non-rhabdoid tumor, which shares molecular similarities with the ATRT-TYR subgroup but has distinct histopathological features and favorable long-term outcome., (© 2016 International Society of Neuropathology.)

Background: Astroblastomas (ABs) are rare glial tumors showing overlapping features with astrocytomas, ependymomas, and sometimes other glial neoplasms, and may be challenging to diagnose., Methods: We examined clinical, histopathological, and molecular features in 28 archival formalin-fixed, paraffin-embedded AB cases and performed survival analyses using Cox proportional hazards and Kaplan-Meier methods., Results: Unlike ependymomas and angiocentric gliomas, ABs demonstrate abundant distinctive astroblastic pseudorosettes and are usually Olig2 immunopositive. They also frequently exhibit rhabdoid cells, multinucleated cells, and eosinophilic granular material. They retain immunoreactivity to alpha thalassemia/mental retardation syndrome X-linked, are immunonegative to isocitrate dehydrogenase-1 R132H mutation, and only occasionally show MGMT promoter hypermethylation differentiating them from many diffuse gliomas. Like pleomorphic xanthoastrocytoma, ganglioglioma, supratentorial pilocytic astrocytoma, and other predominantly cortical-based glial tumors, ABs often harbor the BRAF V600E mutation, present in 38% of cases tested (n = 21), further distinguishing those tumors from ependymomas and angiocentric gliomas. Factors correlating with longer patient survival included age less than 30 years, female gender, absent BRAF V600E , and mitotic index less than 5 mitoses/10 high-power fields; however, only the latter was significant by Cox and Kaplan-Meier analyses (n = 24; P = .024 and .012, respectively). This mitotic cutoff is therefore currently the best criterion to stratify tumors into low-grade ABs and higher-grade anaplastic ABs., Conclusions: In addition to their own characteristic histological features, ABs share some molecular and histological findings with other, possibly ontologically related, cortical-based gliomas of mostly children and young adults. Importantly, the presence of BRAF V600E mutations in a subset of ABs suggests potential clinical utility of targeted anti-BRAF therapy., (© The Author(s) 2016. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objective: In meningioma, correlation of brain invasion with prognosis and clinical variables remains controversial., Methods: Correlation of brain invasion with clinical and histopathologic variables was investigated in 467 patients with primary intracranial meningioma., Results: Diffuse (n = 3; 10%), clusterlike (n = 11; 34%) or fingerlike (n = 18; 56%) invasion was detected in 32 patients (7%). Brain invasion was more common in males than in females (13% vs. 5%; odds ratio, 2.75; 95% confidence interval, 1.29-5.89; P = 0.009) and pattern of invasion differed between genders (P = 0.037). Brain invasion was absent in 401 benign meningiomas and present in 48% of 60 atypical (n = 29) and 50% of 6 anaplastic (n = 3) meningiomas (P < 0.001) but was independent of tumor location and extent of resection. Progression occurred in 11% and was more frequent (31% vs. 15%; P = 0.036) in invasive than in noninvasive tumors, but only after gross total resection and in univariate analyses, and independent of invasion pattern. In atypical meningiomas, frequency of adjuvant irradiation was similar comparing invasive and noninvasive tumors and grading solely based on brain invasion (n = 20; 33%), other World Health Organization (WHO) criteria (n = 31; 52%) or a combination of both (n = 9; 15%). Risk of recurrence was lower (hazard ratio, 0.258, 95% confidence interval, 0.09-0.734; P = 0.011) when grading exclusively based on brain invasion than when further WHO criteria were in addition present and the progression-free interval among the first was similar to benign tumors., Conclusions: Brain invasion and its patterns are correlated to gender. In contrast to the current WHO classification, invasion was associated with recurrence only after gross total resection and not independent of further histopathologic criteria of atypia., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The majority of glioblastomas develop rapidly with a short clinical history (primary glioblastoma IDH wild-type), whereas secondary glioblastomas progress from diffuse astrocytoma or anaplastic astrocytoma. IDH mutations are the genetic hallmark of secondary glioblastomas. Gliosarcomas and giant cell glioblastomas are rare histological glioblastoma variants, which usually develop rapidly. We determined the genetic patterns of 36 gliosarcomas and 19 giant cell glioblastomas. IDH1 and IDH2 mutations were absent in all 36 gliosarcomas and in 18 of 19 giant cell glioblastomas analyzed, indicating that they are histological variants of primary glioblastoma. Furthermore, LOH 10q (88%) and TERT promoter mutations (83%) were frequent in gliosarcomas. Copy number profiling using the 450k methylome array in 5 gliosarcomas revealed CDKN2A homozygous deletion (3 cases), trisomy chromosome 7 (2 cases), and monosomy chromosome 10 (2 cases). Giant cell glioblastomas had LOH 10q in 50% and LOH 19q in 42% of cases. ATRX loss was detected immunohistochemically in 19% of giant cell glioblastomas, but absent in 17 gliosarcomas. These and previous results suggest that gliosarcomas are a variant of, and genetically similar to, primary glioblastomas, except for a lack of EGFR amplification, while giant cell glioblastoma occupies a hybrid position between primary and secondary glioblastomas., (© 2015 International Society of Neuropathology.)

Dysembryoplastic neuroepithelial tumor (DNET) is a benign brain tumor associated with intractable drug-resistant epilepsy. In order to identify underlying genetic alterations and molecular mechanisms, we examined three family members affected by multinodular DNETs as well as 100 sporadic tumors from 96 patients, which had been referred to us as DNETs. We performed whole-exome sequencing on 46 tumors and targeted sequencing for hotspot FGFR1 mutations and BRAF p.V600E was used on the remaining samples. FISH, copy number variation assays and Sanger sequencing were used to validate the findings. By whole-exome sequencing of the familial cases, we identified a novel germline FGFR1 mutation, p.R661P. Somatic activating FGFR1 mutations (p.N546K or p.K656E) were observed in the tumor samples and further evidence for functional relevance was obtained by in silico modeling. The FGFR1 p.K656E mutation was confirmed to be in cis with the germline p.R661P variant. In 43 sporadic cases, in which the diagnosis of DNET could be confirmed on central blinded neuropathology review, FGFR1 alterations were also frequent and mainly comprised intragenic tyrosine kinase FGFR1 duplication and multiple mutants in cis (25/43; 58.1 %) while BRAF p.V600E alterations were absent (0/43). In contrast, in 53 cases, in which the diagnosis of DNET was not confirmed, FGFR1 alterations were less common (10/53; 19 %; p < 0.0001) and hotspot BRAF p.V600E (12/53; 22.6 %) (p < 0.001) prevailed. We observed overexpression of phospho-ERK in FGFR1 p.R661P and p.N546K mutant expressing HEK293 cells as well as FGFR1 mutated tumor samples, supporting enhanced MAP kinase pathway activation under these conditions. In conclusion, constitutional and somatic FGFR1 alterations and MAP kinase pathway activation are key events in the pathogenesis of DNET. These findings point the way towards existing targeted therapies.

Papillary tumor of the pineal region (PTPR) is a neuroepithelial brain tumor, which might pose diagnostic difficulties and recurs often. Little is known about underlying molecular alterations. We therefore investigated chromosomal copy number alterations, DNA methylation patterns and mRNA expression profiles in a series of 24 PTPRs. Losses of chromosome 10 were identified in all 13 PTPRs examined. Losses of chromosomes 3 and 22q (54%) as well as gains of chromosomes 8p (62%) and 12 (46%) were also common. DNA methylation profiling using Illumina 450k arrays reliably distinguished PTPR from ependymomas and pineal parenchymal tumors of intermediate differentiation. PTPR could be divided into two subgroups based on methylation pattern, PTPR group 2 showing higher global methylation and a tendency toward shorter progression-free survival (P = 0.06). Genes overexpressed in PTPR as compared with ependymal tumors included SPDEF, known to be expressed in the rodent subcommissural organ. Notable SPDEF protein expression was encountered in 15/19 PTPRs as compared with only 2/36 ependymal tumors, 2/19 choroid plexus tumors and 0/23 samples of other central nervous system (CNS) tumor entities. In conclusion, PTPRs show typical chromosomal alterations as well as distinct DNA methylation and expression profiles, which might serve as useful diagnostic tools., (© 2015 International Society of Neuropathology.)

Pilocytic astrocytoma (PA) is the most common brain tumor in children but is rare in adults, and hence poorly studied in this age group. We investigated 222 PA and report increased aneuploidy in older patients. Aneuploid genomes were identified in 45% of adult compared with 17% of pediatric PA. Gains were non-random, favoring chromosomes 5, 7, 6 and 11 in order of frequency, and preferentially affecting non-cerebellar PA and tumors with BRAF V600E mutations and not with KIAA1549-BRAF fusions or FGFR1 mutations. Aneuploid PA differentially expressed genes involved in CNS development, the unfolded protein response, and regulators of genomic stability and the cell cycle (MDM2, PLK2),whose correlated programs were overexpressed specifically in aneuploid PA compared to other glial tumors. Thus, convergence of pathways affecting the cell cycle and genomic stability may favor aneuploidy in PA, possibly representing an additional molecular driver in older patients with this brain tumor.

IDH wild type (IDHwt) anaplastic astrocytomas WHO grade III (AA III) are associated with poor outcome. To address the possibilities of molecular subsets among astrocytoma or of diagnostic reclassification, we analyzed a series of 160 adult IDHwt tumors comprising 120 AA III and 40 diffuse astrocytomas WHO grade II (A II) for molecular hallmark alterations and established methylation and copy number profiles. Based on molecular profiles and hallmark alterations the tumors could be grouped into four major sets. 124/160 (78 %) tumors were diagnosed as the molecular equivalent of conventional glioblastoma (GBM), and 15/160 (9 %) as GBM-H3F3A mutated (GBM-H3). 13/160 (8 %) exhibited a distinct methylation profile that was most similar to GBM-H3-K27, however, lacked the H3F3A mutation. This group was enriched for tumors of infratentorial and midline localization and showed a trend towards a more favorable prognosis. All but one of the 120 IDHwt AA III could be assigned to these three groups. 7 tumors recruited from the 40 A II, comprised a variety of molecular signatures and all but one were reclassified into distinct WHO entities of lower grades. Interestingly, TERT mutations were exclusively restricted to the molecular GBM (78 %) and associated with poor clinical outcome. However, the GBM-H3 group lacking TERT mutations appeared to fare even worse. Our data demonstrate that most of the tumors diagnosed as IDHwt astrocytomas can be allocated to other tumor entities on a molecular basis. The diagnosis of IDHwt diffuse astrocytoma or anaplastic astrocytoma should be used with caution.

Astrocytoma and oligodendroglioma are histologically and genetically well-defined entities. The majority of astrocytomas harbor concurrent TP53 and ATRX mutations, while most oligodendrogliomas carry the 1p/19q co-deletion. Both entities share high frequencies of IDH mutations. In contrast, oligoastrocytomas (OA) appear less clearly defined and, therefore, there is an ongoing debate whether these tumors indeed constitute an entity or whether they represent a mixed bag containing both astrocytomas and oligodendrogliomas. We investigated 43 OA diagnosed in different institutions employing histology, immunohistochemistry and in situ hybridization addressing surrogates for the molecular genetic markers IDH1R132H, TP53, ATRX and 1p/19q loss. In all but one OA the combination of nuclear p53 accumulation and ATRX loss was mutually exclusive with 1p/19q co-deletion. In 31/43 OA, only alterations typical for oligodendroglioma were observed, while in 11/43 OA, only indicators for mutations typical for astrocytomas were detected. A single case exhibited a distinct pattern, nuclear expression of p53, ATRX loss, IDH1 mutation and partial 1p/19q loss. However, this was the only patient undergoing radiotherapy prior to surgery, possibly contributing to the acquisition of this uncommon combination. In OA with oligodendroglioma typical alterations, the portions corresponding to astrocytic part were determined as reactive, while in OA with astrocytoma typical alterations the portions corresponding to oligodendroglial differentiation were neoplastic. These data provide strong evidence against the existence of an independent OA entity.

Gemistocytic astrocytoma (World Health Organization grade II) is a rare variant of diffuse astrocytoma that is characterized by the presence of neoplastic gemistocytes and has a significantly less favorable prognosis. Other than frequent TP53 mutations (>80%), little is known about its molecular profile. Here, we show that gemistocytic astrocytomas carry a lower frequency of IDH mutations than fibrillary astrocytomas (74% vs 92%; p = 0.0255) but have profiles similar to those of fibrillary astrocytomas with respect to TERT promoter mutations (5% vs 0%), 1p/19q loss (10% vs 8%), and loss of heterozygosity 10q (10% vs 12%). Exome sequencing in 5 gemistocytic astrocytomas revealed homozygous deletion of genes at 19q13 (i.e. RRAS [related RAS viral oncogene homolog; 2 cases] and ERCC1 [excision repair cross-complementing rodent repair deficiency, complementation group 1; 1 case]). Further screening showed RRAS homozygous deletion in 7 of 42 (17%) gemistocytic astrocytomas and in 3 of 24 (13%) IDH1 mutated secondary glioblastomas. Patients with gemistocytic astrocytoma and secondary glioblastoma with an RRAS deletion tended to have shorter survival rates than those without deletion. Differential polymerase chain reaction and methylation-specific polymerase chain reaction revealed an ERCC1 homozygous deletion or promoter methylation in 10 of 42 (24%) gemistocytic astrocytomas and in 8 of 24 (33%) secondary glioblastomas. Alterations in RRAS and ERCC1 appear to be typical in gemistocytic astrocytomas and secondary glioblastomas, since they were not present in 49 fibrillary astrocytomas or 30 primary glioblastomas.

Atypical teratoid/rhabdoid tumours (AT/RT) are malignant brain tumours. Unlike most other human brain tumours, AT/RT are characterized by inactivation of one single gene, SMARCB1. SMARCB1 is a member of the evolutionarily conserved SWI/SNF chromatin remodelling complex, which has an important role in the control of cell differentiation and proliferation. Little is known, however, about the pathways involved in the oncogenic effects of SMARCB1 inactivation, which might also represent targets for treatment. Here we report a comprehensive genetic screen in the fruit fly that revealed several genes not yet associated with loss of snr1, the Drosophila homologue of SMARCB1. We confirm the functional role of identified genes (including merlin, kibra and expanded, known to regulate hippo signalling pathway activity) in human rhabdoid tumour cell lines and AT/RT tumour samples. These results demonstrate that fly models can be employed for the identification of clinically relevant pathways in human cancer.

Synchronous (early) and metachronous (late) brain metastasis (BM) events of sporadic clear cell renal cell carcinoma (ccRCC) (n = 148) were retrospectively analyzed using comparative genomic hybridization (CGH). Using oncogenetic tree models and cluster analyses, chromosomal imbalances related to recurrence-free survival until BM (RFS-BM) were analyzed. Losses at 9p and 9q appeared to be hallmarks of metachronous BM events, whereas an absence of detectable chromosomal changes at 3p was often associated with synchronous BM events. Correspondingly, k-means clustering showed that cluster 1 cases generally exhibited low copy number chromosomal changes that did not involve 3p. Cluster 2 cases had a high occurrence of -9p/-9q (94-98%) deletions, whereas cluster 3 cases had a higher frequency of copy number changes, including loss at chromosome 14 (80%). The higher number of synchronous cases in cluster 1 was also associated with a significantly shorter RFS-BM compared with clusters 2 and 3 (P = 0.02). Conversely, a significantly longer RFS-BM was observed for cluster 2 versus clusters 1 and 3 (P = 0.02). Taken together, these data suggest that metachronous BM events of ccRCC are characterized by loss of chromosome 9, whereas synchronous BM events may form independently of detectable genetic changes at chromosomes 9 and 3p., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Aims: Desmoplastic infantile astrocytoma/ganglioglioma (DIA/DIG) is a rare primary neuroepithelial brain tumour typically affecting paediatric patients younger than 24 months. Knowledge about genetic alterations in DIA/DIG is limited. However, a previous study on BRAF V600E mutation in paediatric glioma revealed a BRAF mutation in one of two tested DIAs/DIGs. The limited number of cases in that study did not allow any conclusion about mutation frequency of BRAF in this tumour entity., Methods: We collected a series of 18 DIAs/DIGs for testing BRAF V600E mutational status by BRAF V600E immunohistochemistry (clone VE1). Cases with sufficient DNA were tested for BRAF V600E mutation by pyrosequencing., Results: Three out of 18 DIAs/DIGs presented with VE1 binding. A considerable proportion of BRAF V600E mutated tumour cells was detected in the cortical tumour component, whereas the pronounced leptomeningeal tumoural stroma was predominantly negative for VE1 binding. Pyrosequencing confirmed BRAF V600E mutation in two of three VE1-positive cases., Conclusion: BRAF V600E mutation affects a subset of DIAs/DIGs and offers new therapeutic opportunities., (© 2013 British Neuropathological Society.)

The spatial extent of transcranial magnetic stimulation (TMS) is of paramount interest for all studies employing this method. It is generally assumed that the induced electric field is the crucial parameter to determine which cortical regions are excited. While it is difficult to directly measure the electric field, one usually relies on computational models to estimate the electric field distribution. Direct electrical stimulation (DES) is a local brain stimulation method generally considered the gold standard to map structure-function relationships in the brain. Its application is typically limited to patients undergoing brain surgery. In this study we compare the computationally predicted stimulation area in TMS with the DES area in six patients with tumors near precentral regions. We combine a motor evoked potential (MEP) mapping experiment for both TMS and DES with realistic individual finite element method (FEM) simulations of the electric field distribution during TMS and DES. On average, stimulation areas in TMS and DES show an overlap of up to 80%, thus validating our computational physiology approach to estimate TMS excitation volumes. Our results can help in understanding the spatial spread of TMS effects and in optimizing stimulation protocols to more specifically target certain cortical regions based on computational modeling.

Papillary tumors of the pineal region are rare glial tumors located in the vicinity of the third ventricle, the clinical behavior of which is often aggressive. Little is known about the prognostic markers that might aid to identify patients at increased risk for recurrence. Therefore, the prognostic value of histopathologic and clinical features was examined in a series of 21 patients. Median age of the 12 male and 9 female patients was 35 years (range, 10 to 56 y). On histopathologic examination, all tumors were characterized by loose papillary structures and tumor cells forming broad perivascular pseudorosettes showing cytokeratin expression. In addition, tumors showed increased cellularity (n=4; 19%), nuclear pleomorphism (n=4; 19%), solid growth (n=11; 52%), necrosis (n=8; 38%), increased mitotic activity (≥3 mitoses per 10 high-power fields [n=10; 48%]), and increased proliferation (Ki67/MIB1 index ≥10% [n=8/20; 40%]). Gross total resection could be achieved in 13/21 patients (62%). Postoperatively, 13 patients received radiotherapy and 4 patients chemotherapy. Median recurrence-free survival was 66 months in 19 patients, for whom detailed follow-up information was available. Twelve patients (63%) experienced tumor progression. Three patients (16%) died of disease. Among the clinical and histopathologic features examined, only increased mitotic activity (52 [8 to 96] vs. 68 [66 to 70] mo [median [95% confidence interval]]) and proliferative activity (29 [0 to 64] vs. 67 [44 to 90] mo) were significantly associated with recurrence (P<0.05). Tumors of the 3 patients who had succumbed to disease showed increased mitotic and proliferative activity. In conclusion, increased mitotic and proliferative activities are associated with worse prognosis in papillary tumors of the pineal region.

Glioblastoma may develop rapidly without evidence for precursor lesions (primary glioblastomas), or progress from diffuse or anaplastic astrocytomas (secondary glioblastomas). Despite having distinct genetic profiles, these glioblastoma subtypes have similar histological features. We hypothesized that the highly malignant phenotype of glioblastoma may be attributable to genetic alterations that are common to both glioblastoma subtypes. In the present study, we first searched for commonly (>35%) amplified genes in glioblastomas with IDH1 mutation (a hallmark of secondary glioblastoma) and those without IDH1 mutation (typical for primary glioblastoma) in data from The Cancer Genome Atlas (TCGA). A total of 25 genes were identified, of which 21 were located at 7q31-34. We then screened 264 gliomas (70 glioblastomas, 112 diffuse astrocytomas, 82 oligodendrogliomas) for gain of the MET at 7q31.2 with quantitative polymerase chain reaction (PCR). MET gain was detected in primary glioblastomas (47%) and secondary glioblastomas (44%), suggesting that this genetic alteration plays a role in the pathogenesis of both glioblastoma subtypes. MET gain was also common in diffuse astrocytomas (38%), but less frequent in oligodendrogliomas (16%). MET gain in diffuse astrocytomas was associated with shorter survival (median, 43.0 vs. 70.7 months; P = 0.004), suggesting that MET gain is a useful prognostic marker for diffuse astrocytomas., (© 2012 The Authors; Brain Pathology © 2012 International Society of Neuropathology.)

Glioblastomas with a proneural expression signature are characterized by frequent IDH1 mutations (i.e. genetic hallmarks of secondary glioblastomas) and PDGFRA (platelet-derived growth factor receptor-α) amplification. Mutations in IDH1/2 are frequent and early genetic events in diffuse astrocytomas (World Health Organization grade II), precursor to secondary glioblastomas, but little is known about the role and timing of PDGFRA amplification in these tumors. We assessed PDGFRA gain in 342 low-grade diffuse gliomas by quantitative polymerase chain reaction. Gain in PDGFRA was detected in 27 (16.3%) of 166 diffuse astrocytomas, significantly more frequent than in oligodendrogliomas (3 [2.6%] of 115, p < 0.0001). Analyses using previously published data from our laboratory showed an inverse correlation between PDGFRA gain and IDH1/2 mutations (p = 0.018) or 1p/19q loss (p < 0.0001). The vast majority of diffuse astrocytomas showed IDH1/2 mutations and/or PDGFRA gain (154 [93%] of 166). Mean survival of diffuse astrocytoma patients with PDGFRA gain was 8.8 ± 1.6 years, similar to that with IDH1/2 mutations (7.8 ± 0.5 years) or TP53 mutations (7.6 ± 0.6 years) but significantly longer than those with MET gain (4.4 ± 0.7 years). Dual-color fluorescence in situ hybridization in 6 diffuse astrocytomas with PDGFRA/MET co-gain identified by quantitative polymerase chain reaction revealed that PDGFRA and MET were typically amplified in different tumor cell populations. Tumor cells with coamplification were also focally observed, suggesting intratumoral heterogeneity, even in diffuse astrocytomas.

Chromosomal 7q34 duplication and BRAF-KIAA1549 fusion is a characteristic genetic alteration in pilocytic astrocytomas. 7q34 gain appears to be common in diffuse astrocytomas, but its significance is unclear. We assessed BRAF gain and BRAF mutations in 123 low-grade diffuse gliomas, including 55 diffuse astrocytomas, 18 oligoastrocytomas and 50 oligodendrogliomas. Quantitative polymerase chain reaction (PCR) revealed BRAF gain in 17/50 (34%) oligodendrogliomas, a significantly higher frequency than in diffuse astrocytomas (7/55; 13%; P = 0.0112). BRAF gain was common in low-grade diffuse gliomas with 1p/19q loss (39%) and those lacking any of the genetic alterations analyzed (31%), but was rare in those with TP53 mutations (2%). Logistic regression analysis showed a significant positive association between 1p/19q loss and BRAF gain (P = 0.0032) and a significant negative association between TP53 mutations and BRAF gain (P = 0.0042). Fluorescence in situ hybridization (FISH) analysis of 26 low-grade diffuse gliomas with BRAF gain additionally revealed BRAF-KIAA1549 fusion in one oligodendroglioma. Sequencing of cDNA in 17 low-grade diffuse gliomas showed BRAF-KIAA1549 fusion in another oligodendroglioma. A BRAF(V600E) mutation was also detected in one oligodendroglioma, and a BRAF(A598V) in one diffuse astrocytoma. These results suggest that low-grade diffuse gliomas with 1p/19q loss have frequent BRAF gains, and a small fraction of oligodendrogliomas may show BRAF-KIAA1549 fusion., (© 2012 The Authors; Brain Pathology © 2012 International Society of Neuropathology.)

Gliosarcoma is a rare variant of glioblastoma characterized by a biphasic pattern of glial and mesenchymal differentiation. It is unclear whether mesenchymal differentiation in gliosarcomas is because of extensive genomic instability and/or to a mechanism similar to epithelial-mesenchymal transition (EMT). In the present study, we assessed 40 gliosarcomas for immunoreactivity of Slug, Twist, matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9), which are involved in EMT in epithelial tumors. Nuclear Slug expression was observed in >50% of neoplastic cells in mesenchymal tumor areas of 33 (83%) gliosarcomas, but not in glial areas (P < 0.0001). Nuclear Twist expression was observed in >50% of neoplastic cells in mesenchymal tumor areas of 35 (88%) gliosarcomas, but glial tumor areas were largely negative except in four cases (P < 0.0001). Expression of MMP-2 and MMP-9 was also significantly more extensive in mesenchymal than in glial tumor areas. None of 20 ordinary glioblastomas showed Slug or Twist expression in >10% neoplastic cells. Thus, expression of Slug, Twist, MMP-2 and MMP-9 was characteristic of mesenchymal tumor areas of gliosarcomas, suggesting that mechanisms involved in the EMT in epithelial neoplasms may play roles in mesenchymal differentiation in gliosarcomas., (© 2012 The Authors; Brain Pathology © 2012 International Society of Neuropathology.)

Primary glioblastomas develop with a short clinical history, without evidence for less malignant precursor lesions, while secondary glioblastomas slowly develop via progression from diffuse astrocytoma (WHO grade II) or anaplastic astrocytoma (WHO grade III). The time until progression and the clinical outcome of diffuse astrocytomas vary significantly. We have shown that IDH1 mutations reliably distinguish between primary glioblastomas (without IDH1 mutations) and secondary glioblastomas (with IDH1 mutations). The most frequent genetic alteration shared by primary and secondary glioblastomas is loss of heterozygosity at 10q (up to 60% of cases). Here, we first assessed The Cancer Genome Atlas data to identify gene loss at 10q in glioblastomas with or without IDH1 mutations. Using log-ratio thresholds of -1.0, 10 genes were identified; with the log-ratio thresholds of -2.0, only the DMBT1 (deleted in malignant brain tumor 1) gene at 10q26.13 remained as a deleted gene in glioblastomas with or without IDH1 mutations (12.5% vs 8.0%). We then analyzed a total of 404 gliomas by differential polymerase chain reaction and found a DMBT1 homozygous deletion at a similar frequency in primary and secondary glioblastomas (19.6% vs 20.8%). A fraction (11.3%) of diffuse astrocytomas showed a DMBT1 homozygous deletion that was significantly associated with a shorter overall survival (52.8 vs 84.0 months; p = 0.003). These results indicate that a DMBT1 homozygous deletion is present in a fraction of diffuse astrocytomas and that it is associated with an unfavorable clinical outcome.

Objective: To analyze infiltration patterns of IDH1 mutant diffuse gliomas into the brain by identification of single tumor cells applying an antibody specific to mutant IDH1 R132H protein., Design: Immunohistochemical analysis., Setting: University hospital., Patients: Whole-brain and hemisphere sections of 4 patients diagnosed with diffuse glioma., Results: Tumor cells were identified in areas that appeared inconspicuous macroscopically and at histological analysis with respect to cellularity, cellular pleomorphism, or mitotic activity in all cases., Conclusion: Detection of single tumor cells throughout the brain demonstrates diffuse glioma to represent systemic brain disease.

Background: The clinical impact of routine neuropathologic examination of samples from patients with intracerebral hemorrhage (ICH) is unclear., Methods: Therefore, we evaluated a consecutive series of 378 surgical specimens from patients with ICH concerning demographic data, localization of hemorrhage, preoperative clinical diagnosis and neuropathological diagnosis., Results: Histological examination revealed the putative origin of ICH in 143 cases (37.8%). Vascular pathologies were detected in 127 patients (33.6%), while tumors were identified in 9 patients (2.4%), infarction in 6 patients (1.6%) and abscess in 1 patient (0.3%). Preoperatively, tumor was considered in 65 patients (17.2%), while vascular malformations were supposed in 94 patients (24.9%), infarction in 18 cases (4.8%) and abscess in 3 cases (0.8%). In 198 patients (52.4%) no specific assumption was made., Conclusions: Comparing preoperative assumptions and histological diagnoses, tumor, vascular malformations and infarctions were clinically overestimated, while arteriolosclerosis and amyloid angiopathy were underestimated. In conclusion, we found that histological findings potentially affecting clinical management and prognosis were obtained in 37.8% of cases. Our data suggest that histopathological examination of intracerebral hemorrhage provides important information for patient management and should be routinely performed.

Aim: Duplication of 7q34 resulting in generation of BRAF-KIAA1549 fusion transcripts is a characteristic event in pilocytic astrocytoma that may also aid distinction from diffuse astrocytic tumours. As data on BRAF-KIAA1549 fusion transcript status remain mainly limited to children, we aimed to examine the diagnostic value of BRAF-KIAA1549 fusion transcripts across all age groups., Methods: BRAF-KIAA1549 fusion transcript status was examined using reverse transcription polymerase chain reaction on formalin-fixed paraffin-embedded samples of 105 primary pilocytic astrocytomas [median patient age: 17 years (1-74 years)]., Results: Informative results (distinct wildtype BRAF bands detectable) were obtained in 105/124 cases (85%). Fusion transcripts were detected in 53 of cases (51%). They were more often encountered in tumours of infratentorial location [42/67 (63%) vs. 11/38 (29%)] and comprised KIAA1549-Ex16&#95;BRAF-Ex9 (32 cases), KIAA1549-Ex15&#95;BRAF-Ex9 (14 cases) and KIAA1549-Ex16&#95;BRAF-Ex11 (seven cases). Fusion transcripts were present in 79% of tumours diagnosed in the first decade of life, but only in 51% of patients aged 11-20 years, 42% of patients aged 21-30 years, 30% of patients aged 31-40 years and 7% of patients older than 40 years. On multivariate logistic regression analysis, the association of fusion transcript status and age was confirmed adjusting for tumour location (P = 0.006)., Conclusions: The frequency of BRAF-KIAA1549 fusion transcripts is significantly lower in adult patients with pilocytic astrocytoma, weakening the sensitivity of this specific diagnostic marker in that age group., (© 2011 The Authors. Neuropathology and Applied Neurobiology © 2011 British Neuropathological Society.)

We recently reported that the vast majority (>90%) of low-grade diffuse gliomas (diffuse astrocytoma, oligoastrocytoma and oligodendroglioma) carry at least one of the following genetic alterations: IDH1/2 mutation, TP53 mutation or 1p/19q loss. Only 7% of cases were triple-negative (ie, lacking any of these alterations). In the present study, array comparative genomic hybridization (CGH) in 15 triple-negative WHO grade II gliomas (eight diffuse astrocytomas and seven oligodendrogliomas) showed loss at 9p21 (p14(ARF) , p15(INK4b) , p16(INK4a) loci) and 13q14-13q32 (containing the RB1 locus) in three and two cases, respectively. Further analyses in 31 triple-negative cases as well as a total of 160 non-triple-negative cases revealed that alterations in the RB1 pathway (homozygous deletion and promoter methylation of the p15(INK4b) , p16(INK4a) and RB1 genes) were significantly more frequent in triple-negative (26%) than in non-triple-negative cases (11%; P = 0.0371). Multivariate analysis after adjustment for age, histology and treatment showed that RB1 pathway alterations were significantly associated with unfavorable outcome for patients with low-grade diffuse glioma [hazard ratio, 3.024 (1.279-6.631); P = 0.0057]. These results suggest that a fraction of low-grade diffuse gliomas lacking common genetic alterations may develop through a distinct genetic pathway, which may include loss of cell-cycle control regulated by the RB1 pathway., (© 2011 The Authors; Brain Pathology © 2011 International Society of Neuropathology.)

Atypical teratoid/rhabdoid tumors (AT/RTs) are highly aggressive brain tumors of early childhood poorly responding to therapy. The majority of cases show inactivation of SMARCB1 (INI1, hSNF5, BAF47), a core member of the adenosine triphosphate (ATP)-dependent SWI/SNF chromatin-remodeling complex. We here report the case of a supratentorial AT/RT in a 9-month-old boy, which showed retained SMARCB1 staining on immunohistochemistry and lacked genetic alterations of SMARCB1. Instead, the tumor showed loss of protein expression of another SWI/SNF chromatin-remodeling complex member, the ATPase subunit SMARCA4 (BRG1) due to a homozygous SMARCA4 mutation [c.2032C>T (p.Q678X)]. Our findings highlight the role of SMARCA4 in the pathogenesis of SMARCB1-positive AT/RT and the usefulness of antibodies directed against SMARCA4 in this diagnostic setting.

Platelet-derived growth factor receptor (PDGFR) signaling has been implicated in the pathogenesis of glioblastomas and represents a target for the tyrosine kinase inhibitor imatinib. To examine the prognostic or predictive role of PDGFRs in recurrent glioblastomas, expression was examined in tumor samples of 101 patients of CSTI571BDE40, a randomized trial comparing hydroxyurea monotherapy and a combination of hydroxyurea and imatinib. Furthermore, PDGFRα phosphorylation was investigated using in situ proximity ligation assay. PDGFRα protein was expressed in 33% of tumors and was associated with male sex, young age, presence of R132H mutated isocitrate dehydrogenase 1 protein and short median survival (142 vs. 187 days, p = 0.028). Tumor PDGFRα phosphorylation was also associated with short survival (p = 0.030). The subset of patients with PDGFRα positive glioblastoma did not have longer survival on treatment with hydroxyurea and imatinib compared with hydroxyurea monotherapy. In conclusion, both PDGFRα protein expression and phosphorylation status had a prognostic role in recurrent glioblastomas but did not define a group that showed benefit from the combination therapy consisting of hydroxyurea and imatinib., (Copyright © 2010 UICC.)

The current World Health Organization classification recognizes three histological types of grade II low-grade diffuse glioma (diffuse astrocytoma, oligoastrocytoma, and oligodendroglioma). However, the diagnostic criteria, in particular for oligoastrocytoma, are highly subjective. The aim of our study was to establish genetic profiles for diffuse gliomas and to estimate their predictive impact. In this study, we screened 360 World Health Organization grade II gliomas for mutations in the IDH1, IDH2, and TP53 genes and for 1p/19q loss and correlated these with clinical outcome. Most tumors (86%) were characterized genetically by TP53 mutation plus IDH1/2 mutation (32%), 1p/19q loss plus IDH1/2 mutation (37%), or IDH1/2 mutation only (17%). TP53 mutations only or 1p/19q loss only was rare (2 and 3%, respectively). The median survival of patients with TP53 mutation ± IDH1/2 mutation was significantly shorter than that of patients with 1p/19q loss ± IDH1/2 mutation (51.8 months vs. 58.7 months, respectively; P = 0.0037). Multivariate analysis with adjustment for age and treatment confirmed these results (P = 0.0087) and also revealed that TP53 mutation is a significant prognostic marker for shorter survival (P = 0.0005) and 1p/19q loss for longer survival (P = 0.0002), while IDH1/2 mutations are not prognostic (P = 0.8737). The molecular classification on the basis of IDH1/2 mutation, TP53 mutation, and 1p/19q loss has power similar to histological classification and avoids the ambiguity inherent to the diagnosis of oligoastrocytoma.

Side population (SP) cells identified using the Hoechst 33342 fluorescent dye efflux technique overlap with the tumor stem cell fraction that is responsible for tumorigenesis and recurrence in malignant gliomas. Because diffuse invasion of glioma cells represents the main obstacle to successful therapy and underlies recurrence, we examined the existence of an SP fraction in 8 human glioma cell lines and in a sample of primary glioblastoma (GBM) cells and compared the migration potential of SP cells with that of non-SP cells. The SP cells were detected in U373MG (1.5%), U87MG (1.9%), H4 (2.2%), and primary GBM cells (1.5%). The SP cells displayed approximately 2-fold higher expression of ABCG2, the transporter that is mainly responsible for dye efflux. In monolayer and transwell assays, the migration of SP cells was lower than that of non-SP cells. Furthermore, there was a distinct SP in GBM cells selected for slow migration but not in their fast counterparts. The finding that SP cells have a lower migration potential than non-SP cells suggests that cells underlying the initiation and recurrence of gliomas are able to migrate, albeit less so than other glioma cells. These data may also provide an explanation for the clinical observation that most GBM recur in close proximity to the site of the original tumor.

Systemic cancer is the second most common cause of death in developed countries and metastatic brain tumour the most common tumour of the central nervous system (CNS). As the incidence of brain metastases appears to be rising, more accurate non-invasive imaging modalities for diagnosis, prognosis, prediction and follow-up of treatment are requisites for efficient patient management. Positron emission tomography (PET) imaging has the ability to evaluate different aspects of tumour microenvironment on the molecular and cellular level and impact the workup of patients with brain metastasis. This article reviews the current application of PET imaging in patients with metastatic brain disease.

Atypical teratoid/rhabdoid tumors are malignant embryonal tumors characterized by the presence of rhabdoid cells, genetic alterations affecting the SMARCB1 gene (hSNF5/INI1), and a poor prognosis. Whether INI1 plays a role in the pathogenesis of other central nervous system tumors is uncertain. We report on cases of 2 young children with unusual intracranial nonrhabdoid neuroectodermal tumors within and around the third or fourth ventricle that are characterized by cribriform strands and trabeculae and well-defined epithelial membrane antigen-immunopositive surfaces and show INI1 protein loss. Histological and immunohistochemical features did not correspond to established tumor types, including atypical teratoid/rhabdoid tumors, medulloepithelioma, choroid plexus carcinoma, and ependymoma. Fluorescence in situ hybridization analyses failed to identify chromosomal alterations affecting the SMARCB1 locus, but sequencing revealed a homozygous 4-bp duplication in exon 4 (492duplCCTT) in one of the tumors. Both children responded well to conventional adjuvant therapy protocols and are alive and in complete remission longer than 5 years postoperatively. We suggest that cribriform neuroepithelial tumor (CRINET) is a nonrhabdoid ventricular tumor that shows loss of tumoral INI1 protein and has a relatively favorable prognosis.