Application of multiplex ligation-dependent probe amplification (MLPA) and low pass whole genome sequencing (LP-WGS) to the classification / characterisation of low grade glioneuronal tumours.

AIMS: Glioneuronal tumours, although rare, are an important cause of treatment-resistant epilepsy. Differential diagnosis of glioneuronal tumour subtypes is complicated by their variable histological appearance and the lack of pathognomonic histological or molecular biomarkers. In this study we have applied techniques available in a diagnostic laboratory setting to characterise molecular and cytogenetic abnormalities in a single institution cohort of glioneuronal tumours. METHODS: A cohort of 29 glioneuronal tumours that included 21 gangliogliomas and 5 dysembryoplastic neuroepithelial tumours (DNETs) was analysed using low pass whole genome sequencing (WGS) and 2 multiplex ligation-dependent probe amplification (MLPA) central nervous system (CNS) tumour probesets. RESULTS: Low pass WGS identified chromosomal or subchromosomal alterations in 15 specimens. The most common chromosomal alterations were gains of chromosome 7 (n = 8) and chromosome 16 (n = 3). The BRAFV600E mutation was detected by MLPA in 9/21 (42.9%) gangliogliomas and 2/2 pleomorphic xanthoastrocytomas (PXAs). Chromosome 7 gains detected by WGS were reflected in MLPAs by overall gains of chromosome 7 gene probes, including those for BRAF, KIAA1549 and EGFR, while an internal BRAF/MKRN1 duplication was detected in a single ganglioglioma. Homozygous CDKN2A/B loss was detected by MLPA in 3 gangliogliomas, with p16 immunohistochemistry supporting these results. CONCLUSIONS: The combination of low pass WGS and MLPA identifies multiple, diverse genetic and chromosomal alterations in glioneuronal tumours, irrespective of histological tumour grade.

Review: Challenges in the histopathological classification of ganglioglioma and DNT: microscopic agreement studies and a preliminary genotype-phenotype analysis.

Low-grade epilepsy-associated brain tumours (LEAT) are the second most common cause for drug-resistant, focal epilepsy, that is ganglioglioma (GG) and dysembryoplastic neuroepithelial tumours (DNT). However, molecular pathogenesis, risk factors for malignant progression and their frequent association with drug-resistant focal seizures remain poorly understood. This contrasts recent progress in understanding the molecular-genetic basis and targeted treatment options in diffuse gliomas. The Neuropathology Task Force of the International League Against Epilepsy examined available literature to identify common obstacles in diagnosis and research of LEAT. Analysis of 10 published tumour series from epilepsy surgery pointed to poor inter-rater agreement for the histopathology diagnosis. The Task Force tested this hypothesis using a web-based microscopy agreement study. In a series of 30 LEAT, 25 raters from 18 countries agreed in only 40% of cases. Highest discordance in microscopic diagnosis occurred between GG and DNT variants, when oligodendroglial-like cell patterns prevail, or ganglion cells were difficult to discriminate from pre-existing neurons. Suggesting new terminology or major histopathological criteria did not satisfactorily increase the yield of histopathology agreement in four consecutive trials. To this end, the Task Force applied the WHO 2016 strategy of integrating phenotype analysis with molecular-genetic data obtained from panel sequencing and 450k methylation arrays. This strategy was helpful to distinguish DNT from GG variants in all cases. The Task Force recommends, therefore, to further develop diagnostic panels for the integration of phenotype-genotype analysis in order to reliably classify the spectrum of LEAT, carefully characterize clinically meaningful entities and make better use of published literature.

New classification of epilepsy-related neoplasms: The clinical perspective.

Neoplastic CNS lesions are a common cause of focal epilepsy refractory to anticonvulsant treatment, i.e. long-term epilepsy-associated tumors (LEATs). Epileptogenic tumors encompass a variety of intriguing lesions, e.g. dysembryoplastic neuroepithelial tumors or gangliogliomas, which differ from more common CNS neoplasms in their clinical context as well as on histopathology. Long-term epilepsy-associated tumor classification is a rapidly evolving issue in surgical neuropathology, with new entities still being elucidated. One major issue to be resolved is the inconsistent tissue criteria applied to LEAT accounting for high diagnostic variability between individual centers and studies, a problem recently leading to a proposal for a new histopathological classification by Blümcke et al. in Acta Neuropathol. 2014; 128: 39-54. While a new approach to tissue diagnosis is appreciated and needed, histomorphological criteria alone will not suffice and we here approach the situation of encountering a neoplastic lesion in an epilepsy patient from a clinical perspective. Clinical scenarios to be supported by an advanced LEAT classification will be illustrated and discussed.

Atypical pediatric ganglioglioma is common and associated with a less favorable clinical course.

OBJECT Ganglioglioma (GG) is commonly recognized as a low-grade tumor located in the temporal lobe, often presenting with seizures. Most are amenable to complete resection and are associated with excellent oncological outcome. The authors encountered several GGs in various locations, which seem to have a less favorable clinical course than GGs in the temporal lobe. METHODS The authors performed a single-center retrospective review of all children with a histological diagnosis of GG who were treated at Children's Hospital Colorado between 1997 and 2013. Each tumor was categorized by 2 pediatric neuroradiologists as typical or atypical based on preoperative MRI appearance. Typical lesions were cortically based, within a single cerebral lobe, well-circumscribed, and solid or mixed solid/cystic. The treatment and clinical course of each patient was analyzed. RESULTS Thirty-seven children were identified, with a median age at presentation of 8.2 years and median follow-up of 38.0 months. Eighteen tumors (48.6%) were typical and 19 (51.4%) were atypical. All typical lesions presented with seizures, whereas no atypical lesions did so. Sixteen (88.9%) typical lesions were located in the temporal lobe. In the atypical group, tumor location was variable, including 11 (57.9%) in the brainstem. Death during follow-up was statistically more common in the atypical group (31.6% vs 0%, p = 0.02). Gross-total resection (GTR) was achieved for 15 of 16 typical tumors (93.8%), compared with 3 atypical tumors (15.8%, p < 0.0001). Presentation with seizure or non-brainstem location were each associated with survival (p = 0.02 and 0.004, respectively). The presence of mutation in BRAF exon 15 did not differ between the 2 groups. CONCLUSIONS Pediatric GG with typical imaging features is associated with excellent rates of GTR and overall survival. Atypical GG is commonly encountered, less amenable to GTR, and associated with a worse outcome. This may relate to anatomical or biological characteristics and merits further investigation.

Posterior fossa and spinal gangliogliomas form two distinct clinicopathologic and molecular subgroups.

BACKGROUND: Gangliogliomas are low-grade glioneuronal tumors of the central nervous system and the commonest cause of chronic intractable epilepsy. Most gangliogliomas (>70%) arise in the temporal lobe, and infratentorial tumors account for less than 10%. Posterior fossa gangliogliomas can have the features of a classic supratentorial tumor or a pilocytic astrocytoma with focal gangliocytic differentiation, and this observation led to the hypothesis tested in this study - gangliogliomas of the posterior fossa and spinal cord consist of two morphologic types that can be distinguished by specific genetic alterations. RESULTS: Histological review of 27 pediatric gangliogliomas from the posterior fossa and spinal cord indicated that they could be readily placed into two groups: classic gangliogliomas (group I; n = 16) and tumors that appeared largely as a pilocytic astrocytoma, but with foci of gangliocytic differentiation (group II; n = 11). Detailed radiological review, which was blind to morphologic assignment, identified a triad of features, hemorrhage, midline location, and the presence of cysts or necrosis, that distinguished the two morphological groups with a sensitivity of 91% and specificity of 100%. Molecular genetic analysis revealed BRAF duplication and a KIAA1549-BRAF fusion gene in 82% of group II tumors, but in none of the group I tumors, and a BRAF:p.V600E mutation in 43% of group I tumors, but in none of the group II tumors. CONCLUSIONS: Our study provides support for a classification that would divide infratentorial gangliogliomas into two categories, (classic) gangliogliomas and pilocytic astrocytomas with gangliocytic differentiation, which have distinct morphological, radiological, and molecular characteristics.

Ganglion cells in circumscribed astrocytic tumors: possible implication in classification and prognosis / Implicação da presença de células ganglionares na classificação e evolução de tumores astrocíticos circunscritos

INTRODUCTION: Glial and neuroglial cell neoplasms comprise pilocytic astrocytoma (PA), pleomorphic xanthoastrocytoma (PXA) and ganglioglioma (GG), which share various similarities, though PA has better prognosis. As ganglion cells (GC) may be scarce in GG and these gangliogliomas may recur or progress to grade III, an accurate diagnosis is essential. OBJECTIVES: The aim was to identify GC and eosinophilic granular bodies (EGB) in PA and PXA, to evaluate its effect on patient’s outcome and compare them with GG. METHODS: A retrospective analysis of radiological, morphological and follow-up aspects (disease free-survival, recurrence and death) of 30 cases (14 PA, 8 PXA, 8 GG). Hematoxylin and eosin (HE) stained sections were reviewed to identify the presence of neoplastic GC and EGB. They were immunostained for synaptophysin (SYN) and neurofilament (NF). Glial fibrillary acidic protein (GFAP) immunostaining was performed in selected cases. RESULTS: Six PA were reclassified as GG due to the presence of GC by HE or immunohistochemistry. Some EGB resembling degenerate GC were also immunostained for SYN/NF and most of them were negative for GFAP. The mean disease-free survival was 62.16 months. Four tumors recurred and one patient died. All PXA had GC, suggesting that they were variants of GG, 4 of which recurred and one patient died. Mean disease-free survival was 69 months. The radiological aspect was predominantly cystic. CONCLUSION: We propose that PA and PXA with GC or with EGB immunopositive for neuronal markers could be variants of GG, and some EGB may represent degenerate GC. However, the presence of GC does not seem to modify the biological behavior of these neoplasms.

INTRODUÇÃO: As neoplasias circunscritas incluem astrocitoma pilocítico (AP), xantoastrocitoma pleomórfico (XP) e ganglioglioma (GG), que compartilham diversas semelhanças, sendo o AP o de melhor prognóstico. Como as células ganglionares (CG) no GG podem ser escassas e os GGs podem recidivar ou evoluir (grau III), é fundamental o diagnóstico preciso. OBJETIVOS: Identificar CG e corpos granulares eosinofílicos (CGE) em AP e XP, avaliar sua implicação na evolução e comparar com o GG. MÉTODOS: Análise retrospectiva dos aspectos radiológicos, morfológicos e evolutivos (tempo livre de doença, recidiva e óbito) de 30 casos (14 AP, oito XP, oito GG). Cortes corados com hematoxilina e eosina (HE) foram revistos para a identificação da presença de CG neoplásicas e CGE. Estes foram imunomarcados para sinaptofisina (SIN) e neurofilamento (NF) e, em casos selecionados, para glial fibrillary acidic protein (GFAP). RESULTADOS: Seis AP foram reclassificados para GG pela presença de CG (HE ou imunomarcação). Alguns CGE, semelhantes às CG degeneradas, também imunomarcaram para SIN/NF, a maioria sendo negativa para GFAP. O tempo médio livre de doença foi de 62,16 meses. Quatro tumores recidivaram; um deles evoluiu para óbito. Todos os XP possuíam CG, sugerindo que são variantes de GG, dos quais quatro recidivaram (um óbito). O tempo médio livre de doença foi de 69 meses. O aspecto radiológico foi predominantemente cístico. CONCLUSÃO: Sugerimos que AP e XP com CG ou CGE imunopositivos para marcadores neuronais possam ser variantes de GG e alguns CGE representem CG degeneradas; entretanto, a presença de CG ganglionares parece não modificar o comportamento biológico dessas neoplasias.

Desmoplastic ganglioglioma of the spinal cord in a western European hedgehog (Erinaceus europaeus).

Gangliogliomas are composed of neoplastic glial and neuronal cells and are extremely rare tumors of the central nervous system of domestic animals. The present report describes the clinical presentation and the pathomorphological and immunophenotypical characteristics of a desmoplastic ganglioglioma in the spinal cord of a 3-year-old male western European hedgehog (Erinaceus europaeus). Clinically, the hedgehog exhibited a skin wound and therapy-resistant paresis of the left hind limb. Necropsy showed dilatation of the urinary bladder. Histologic examination of the thoracic spinal cord revealed a focally extensive infiltrative mass, which consisted of multiple nodules of smaller bipolar or oligopolar glial cells and variably sized polygonal, ganglionic, neuron-like cells embedded in variable amounts of microcystic neuropilic matrix. An area of spindle-shaped cells arranged in interwoven fascicles and surrounded by a prominent network of reticulin fibers was interpreted as desmoplastic leptomeningeal stroma. Immunohistochemistry revealed a moderate number of glial fibrillary acidic protein and S-100-positive cells and processes. In addition, the ganglionic neuron-like cells expressed neurofilament, microtubule-associated protein-2, and neuron-specific enolase. In summary, this spinal cord tumor was composed of astroglial and neuronal cellular elements, justifying the diagnosis of a desmoplastic ganglioglioma.

The 2007 WHO Classification of Nervous System Tumors: newly recognized members of the mixed glioneuronal group.

The clinical and pathologic features of two glioneuronal neoplasms newly incorporated in the 2007 revision of the WHO classification of nervous system tumors are reviewed. These are the papillary glioneuronal tumor and the rosette-forming glioneuronal tumor of the fourth ventricle.

Mixed glioneuronal tumors: recently described entities.

CONTEXT: Several distinctive mixed glioneuronal tumors that warrant recognition as clinicopathologic entities have been recently described by neuropathologists. OBJECTIVE: To summarize important clinical, radiologic, and pathologic findings for 3 novel glioneuronal tumors (papillary glioneuronal tumor, rosetted glioneuronal tumor, and rosette-forming glioneuronal tumor of the fourth ventricle). DATA SOURCES: Recent reports in the pathology literature and the authors' experience with mixed glioneuronal tumors at a major cancer center. CONCLUSIONS: Histologic features enabling recognition of these recently described glioneuronal tumors are presented along with remarks concerning the classification of mixed neuronal and glial tumors exhibiting unconventional appearances.

Newly defined central nervous system neoplasms.

In recent years, numerous new entities or variants of recognized central nervous system tumors have been described in the literature, and the morphologic spectrum of these neoplasms is delineated incompletely. The accurate diagnosis and classification of these lesions is important to ensure that patients receive adequate therapy and prognostic information. The clinicopathologic features and differential diagnosis of 4 new entities, including the chordoid glioma of the third ventricle, cerebellar liponeurocytoma, atypical teratoid/rhabdoid tumor, and papillary glioneuronal tumor, are discussed in this review.

Papillary glioneuronal tumor--a new variant of benign mixed brain neoplasm.

We report a case of a 14-year-old girl with papillary glioneuronal tumor (PGNT) in right parietal lobe. On MRI the tumor presented as a contrast enhancing mass with small central hypodense area and consisted of areas similar to central neurocytoma intermixed with vessels surrounded with glial cells. There were also small loose areas superficially reminding DNT. Neurocytic component presented strong synaptophysin immunostaining, while intermixed glial element presented GFAP-immunopositivity. Our case is similar to previously reported PGNT, but an important difference lies in not distinct cystic formation and a presence of loose, edematous tissue. PGNT may be regarded as a variant of ganglioglioma or as a complex variant of extraventricular neurocytoma and belongs to a wide group of benign, dysembryoplastic or even hamartomatous neuroepithelial tumors, which may differentiate into both, glial or neuronal direction: pleomorphic astrocytoma may posses neurocytic differentiation, desmoplastic infantile ganglioglioma may be regarded as complex superficial dural astrocytoma and DNT may present gliomatous areas (complex DNT). Also other rare tumors reminding DNT have been reported: DNT-like neoplasm of septum pellucidum and rosetted glioneuronal tumor. From this point of view it is important to remember that such a wide spectrum may be difficult to discriminate into very narrow clinico-pathological entities.

[The revised WHO classification of brain tumors. Radiological aspects of 4 new tumor entities]. / Die revidierte WHO-Klassifikation der Hirntumoren. Radiologische Aspekte unter besonderer Berücksichtigung von vier neuen Tumorentitäten.

PURPOSE: Characterisation of the classification of brain tumours authorized by the WHO. METHOD OF APPRAISAL: This classification was revised and published in its second version. In the revision, some tumours were regrouped histogenetically and some tumour variants were added. Radiologically relevant changes of the classification include the differentiation of four new tumour entities that are easily distinguished by MR imaging. These four tumours belong to the group of childhood tumours or tumours occurring in early adulthood and are characterized by a good prognosis after extirpation. RESULTS OF APPRAISAL: Central neurocytomas are small-cyst ventricular tumours associated with the foramen of Monroi and show moderate contrast enhancement. Infantile desmoplastic gangliogliomas/astrocytomas commonly consist of a solid tumour portion related to the leptomeninges with pronounced contrast enhancement and a typically very large cyst. Pleomorphic xanthoastrocytomas are circumscribed cortical tumours and usually show very moderate gyriform enhancement with only slight signs of a mass effect. Dysembryoblastic neuroepithelial tumours, which originate in the cortical/ subcortical region, likewise show no mass effect; they are characterised by thickening of the cortex from surrounding dysplastic tissue and erosion of the calotte.