Monomorphous Angiocentric Glioma: A Distinctive Epileptogenic Neoplasm With Features of Infiltrating Astrocytoma and Ependymoma

Clinical characteristics and detection of MYB-QKI fusions in patients with angiocentric glioma

PURPOSE

Angiocentric glioma (AG), a benign tumor identified within the last two decades, was officially included in the 2007 WHO Classification of Tumors of the Central Nervous System, WHO grade I. The tumor is relatively rare, with only approximately 100 cases reported. We aim to complement the characteristics and long-term prognosis of AG, as well as to detect MYB-QKI fusions.

METHODS

The characteristics of all cases collected between 1 March 2009 and 1 March 2023 at the Beijing Sanbo Brain Hospital, Capital Medical University, were summarized and analyzed. Additionally, all fourteen patients were tested for MYB-QKI fusions.

RESULTS

AG more predominantly occurs in adolescents (median age 16.5-year-old), and commonly presents with drug-resistant epilepsy. AG is frequently localized in the supratentorial regions and only one patient is in the brainstem. Brain parenchyma atrophy, and stalk-like signs can observe in imaging. Pathologically, tumor cells are perivascular pseudorosettes, presenting immunoreactivity for GFAP, S-100, Vimentin, "dot-like" staining for EMA, and low proliferative activity. Focal cortex dysplasia was observed in four patients. Twelve of fourteen (85.7%) patients were found with MYB-QKI fusions. Completely surgical resection typically has a satisfactory prognosis with long-term follow-up.

CONCLUSION

AG is a rare benign tumor with a favorable prognosis after complete resection, characterized by refractory epilepsy, frequently occurring in adolescents. MYB-QKI fusions were detected in most AG patients, as a good defining genetic alteration pathologically. The potential presence of focal cortical dysplasia (FCD) may affect the prognosis of epilepsy.

Low-grade glioma of the temporal lobe and tumor-related epilepsy in children

PURPOSE

Low-grade glioma is the most common brain tumor among children and adolescents. When these tumors arise in the temporal lobe, patients frequently present with seizures that are poorly controlled with antiepileptic drugs. Here we summarize the clinical features, pathophysiology, preoperative evaluation, surgical treatment, and outcomes of pediatric patients with low-grade gliomas in the temporal lobe.

METHODS

We reviewed the literature on pediatric low-grade gliomas in the temporal lobe, focusing on cohort studies and systematic reviews that described surgical treatment strategies and reported both oncologic and epilepsy outcomes.

RESULTS

The differential diagnoses of pediatric low-grade gliomas in the temporal lobe include ganglioglioma, dysembryoplastic neuroepithelial tumor, desmoplastic infantile ganglioglioma, papillary glioneuronal tumor, pilocytic astrocytoma, pleomorphic xanthoastrocytoma, angiocentric glioma, and polymorphous low-grade neuroepithelial tumor of the young. There is no consensus on the optimal surgical approach for these tumors: lesionectomy alone, or extended lesionectomy with anterior temporal lobectomy, with or without removal of mesial temporal structures. Gross total resection and shorter preoperative duration of epilepsy are strongly associated with favorable seizure outcomes, defined as Engel Class I or Class II, approaching 90% in most series. The risk of surgical complications ranges from 4 to 17%, outweighing the lifetime risks of medically refractory epilepsy.

CONCLUSION

Pediatric patients with temporal low-grade glioma and tumor-related epilepsy are best managed by a multidisciplinary epilepsy surgery team. Early and appropriate surgery leads to prolonged survival and a greater likelihood of seizure freedom, improving their overall quality of life.

Pediatric CNS tumors and 2021 WHO classification: what do oncologists need from pathologists?

The fifth edition of the WHO Classification of Tumors of the Central Nervous System (CNS), published in 2021, established new approaches to both CNS tumor nomenclature and grading, emphasizing the importance of integrated diagnoses and layered reports. This edition increased the role of molecular diagnostics in CNS tumor classification while still relying on other established approaches such as histology and immunohistochemistry. Moreover, it introduced new tumor types and subtypes based on novel diagnostic technologies such as DNA methylome profiling. Over the past decade, molecular techniques identified numerous key genetic alterations in CSN tumors, with important implications regarding the understanding of pathogenesis but also for prognosis and the development and application of effective molecularly targeted therapies. This review summarizes the major changes in the 2021 fifth edition classification of pediatric CNS tumors, highlighting for each entity the molecular alterations and other information that are relevant for diagnostic, prognostic, or therapeutic purposes and that patients' and oncologists' need from a pathology report.

Low-Grade Gliomas: Histological Subtypes, Molecular Mechanisms, and Treatment Strategies

Low-Grade Gliomas (LGGs) represent a diverse group of brain tumors originating from glial cells, characterized by their unique histopathological and molecular features. This article offers a comprehensive exploration of LGGs, shedding light on their subtypes, histological and molecular aspects. By delving into the World Health Organization's grading system, 5th edition, various specificities were added due to an in-depth understanding of emerging laboratory techniques, especially genomic analysis. Moreover, treatment modalities are extensively discussed. The degree of surgical resection should always be considered according to postoperative quality of life and cognitive status. Adjuvant therapies focused on chemotherapy and radiotherapy depend on tumor grading and invasiveness. In the current literature, emerging targeted molecular therapies are well discussed due to their succinctly therapeutic effect; in our article, those therapies are summarized based on posttreatment results and possible adverse effects. This review serves as a valuable resource for clinicians, researchers, and medical professionals aiming to deepen their knowledge on LGGs and enhance patient care.

Case Report: Brainstem angiocentric glioma presenting in a toddler child-diagnostic and therapeutic challenges

Introduction: Angiocentric gliomas (AG) in brainstem location are exceedingly rare and might cause differential diagnostic problems and uncertainty regarding the best therapeutic approach. Hereby, we describe the clinicopathological findings in a brainstem AG presenting in a toddler child and review the literature. Case report: A 2-year-old boy presented with 5 weeks history of gait disturbances, frequent falls, left-sided torticollis and swallowing problems. MRI head showed a T2-hyperintense, partly exophytic mass lesion centred in the pontomedullary region, raising the possibility of diffuse midline glioma. The exophytic component was partially resected by suboccipital craniotomy, leaving intact the infiltrative component. Ventriculoperitoneal shunt was implanted due to postoperative hydrocephalus. Histological examination revealed a moderately cellular tumour consisted of bland glial cells infiltrating the brain parenchyma and radially arranged around the blood vessels. By immunohistochemistry, the tumour strongly expressed S100 and GFAP in addition to intense nestin positivity, while OLIG2 was negative in the perivascular tumour cells. DNA methylation array profiled the tumour as "methylation class diffuse astrocytoma, MYB or MYBL1-altered subtype B (infratentorial)" and an in-frame MYB::QKI fusion was identified by RNA sequencing, confirming the diagnosis of angiocentric glioma. The patient has been initially treated with angiogenesis inhibitor and mTOR inhibitor, and now he is receiving palliative vinblastine. He is clinically stable on 9 months follow-up. Conclusion: Brainstem AG may cause a diagnostic problem, and the surgical and oncological management is challenging due to unresectability and lack of response to conventional chemo-radiation. In the future, genetically-tailored therapies might improve the prognosis.

Pathomorphological Diagnostic Criteria for Focal Cortical Dysplasias and Other Common Epileptogenic Lesions—Review of the Literature

Focal cortical dysplasia (FCD) represents a heterogeneous group of morphological changes in the brain tissue that can predispose the development of pharmacoresistant epilepsy (recurring, unprovoked seizures which cannot be managed with medications). This group of neurological disorders affects not only the cerebral cortex but also the subjacent white matter. This work reviews the literature describing the morphological substrate of pharmacoresistant epilepsy. All illustrations presented in this study are obtained from brain biopsies from refractory epilepsy patients investigated by the authors. Regarding classification, there are three main FCD types, all of which involve cortical dyslamination. The 2022 revision of the International League Against Epilepsy (ILAE) FCD classification includes new histologically defined pathological entities: mild malformation of cortical development (mMCD), mild malformation of cortical development with oligodendroglial hyperplasia in frontal lobe epilepsy (MOGHE), and “no FCD on histopathology”. Although the pathomorphological characteristics of the various forms of focal cortical dysplasias are well known, their aetiologic and pathogenetic features remain elusive. The identification of genetic variants in FCD opens an avenue for novel treatment strategies, which are of particular utility in cases where total resection of the epileptogenic area is impossible.

Benign Glioma

Benign glioma broadly refers to a heterogeneous group of slow-growing glial tumors with low proliferative rates and a more indolent clinical course. These tumors may also be described as "low-grade" glioma (LGG) and are classified as WHO grade I or II lesions according to the Classification of Tumors of the Central Nervous System (CNS) (Louis et al. in Acta Neuropathol 114:97-109, 2007). Advances in molecular genetics have improved understanding of glioma tumorigenesis, leading to the identification of common mutation profiles with significant treatment and prognostic implications. The most recent WHO 2016 classification system has introduced several notable changes in the way that gliomas are diagnosed, with a new emphasis on molecular features as key factors in differentiation (Wesseling and Capper in Neuropathol Appl Neurobiol 44:139-150, 2018). Benign gliomas have a predilection for younger patients and are among the most frequently diagnosed tumors in children and young adults (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). These tumors can be separated into two clinically distinct subgroups. The first group is of focal, well-circumscribed lesions that notably are not associated with an increased risk of malignant transformation. Primarily diagnosed in pediatric patients, these WHO grade I tumors may be cured with surgical resection alone (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). Recurrence rates are low, and the prognosis for these patients is excellent (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). Diffuse gliomas are WHO grade II lesions with a more infiltrative pattern of growth and high propensity for recurrence. These tumors are primarily diagnosed in young adult patients, and classically present with seizures (Pallud et al. Brain 137:449-462, 2014). The term "benign" is a misnomer in many cases, as the natural history of these tumors is with malignant transformation and recurrence as grade III or grade IV tumors (Jooma et al. in J Neurosurg 14:356-363, 2019). For all LGG, surgery with maximal safe resection is the treatment of choice for both primary and recurrent tumors. The goal of surgery should be for gross total resection (GTR), as complete tumor removal is associated with higher rates of tumor control and seizure freedom. Chemotherapy and radiation therapy (RT), while not typically a component of first-line treatment in most cases, may be employed as adjunctive therapy in high-risk or recurrent tumors and in some select cases. The prognosis of benign gliomas varies widely; non-infiltrative tumor subtypes generally have an excellent prognosis, while diffusely infiltrative tumors, although slow-growing, are eventually fatal (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). This chapter reviews the shared and unique individual features of the benign glioma including diffuse glioma, pilocytic astrocytoma and pilomyxoid astrocytoma (PMA), subependymal giant cell astrocytoma (SEGA), pleomorphic xanthoastrocytoma (PXA), subependymoma (SE), angiocentric glioma (AG), and chordoid glioma (CG). Also discussed is ganglioglioma (GG), a mixed neuronal-glial tumor that represents a notable diagnosis in the differential for other LGG (Wesseling and Capper 2018). Ependymomas of the brain and spinal cord, including major histologic subtypes, are discussed in other chapters.

Paediatric-type diffuse low-grade gliomas: a clinically and biologically distinct group of tumours with a favourable outcome

The WHO 2021 classification of central nervous system cancers distinguishes diffuse gliomas that arise in adults (referred to as the "adult type") and those that arise in children (defined as "paediatric") based on clinical and molecular characteristics."). However, paediatric-type gliomas may occasionally be present in younger adults and occasionally adult-type gliomas may occur in children. Diffuse low-grade paediatric glioma includes diffuse astrocytoma altered by MYB or MYBL1, low-grade polymorphic juvenile neuroepithelial tumour, angiocentric glioma, and diffuse low-grade glioma with an altered MAPK pathway. Here, we examine these newly recognised entities according to WHO diagnostic criteria and propose an integrated diagnostic approach that can be used to separate these clinically and biologically distinct tumor groups.

Neuropathology of the temporal lobe

Neuropathological examination of the temporal lobe provides a better understanding and management of a wide spectrum of diseases. We focused on inflammatory diseases, epilepsy, and neurodegenerative diseases, and highlighted how the temporal lobe is particularly involved in those conditions. Although all these diseases are not specific or restricted to the temporal lobe, the temporal lobe is a key structure to understand their pathophysiology. The main histological lesions, immunohistochemical markers, and molecular alterations relevant for the neuropathological diagnostic reasoning are presented in relation to epidemiology, clinical presentation, and radiological findings. The inflammatory diseases section addressed infectious encephalitides and auto-immune encephalitides. The epilepsy section addressed (i) susceptibility of the temporal lobe to epileptogenesis, (ii) epilepsy-associated hippocampal sclerosis, (iii) malformations of cortical development, (iv) changes secondary to epilepsy, (v) long-term epilepsy-associated tumors, (vi) vascular malformations, and (vii) the absence of histological lesion in some epilepsy surgery samples. The neurodegenerative diseases section addressed (i) Alzheimer's disease, (ii) the spectrum of frontotemporal lobar degeneration, (iii) limbic-predominant age-related TDP-43 encephalopathy, and (iv) α-synucleinopathies. Finally, inflammatory diseases, epilepsy, and neurodegenerative diseases are considered as interdependent as some pathophysiological processes cross the boundaries of this classification.

Angiocentric glioma: A case report and review of the literature

BACKGROUND

Angiocentric glioma (AG) is a rare, low-grade glioma with slow growth. In 2007, AG was first classified as a solid tumor according to the WHO classification of the central nervous system (WHO class I). The outcome and prognosis of most of the cases are very good, but a few cases with tumor metastasis and disease progression, even death, have been reported. We report a case and systematically analyze previous literature to increase our understanding of the disease and determine the factors that may affect disease progression to make prognostic judgments.

CASE PRESENTATION

A young male patient complained of a 3-year history of epilepsy. Anti-epileptic drug treatment was ineffective. An imaging examination revealed a lesion in the left parietal cortex area. Thus, the lesion was completely resected. The pathological diagnosis was angiocentric glioma. During a follow-up of two years, the patient had epilepsy relief controlled by sodium valproate and a disease-free period.

CONCLUSION

AG is an epilepsy-related low-grade glioma that heals after complete resection in most reported cases. However, few reported cases have had disease progression and death. This result may be due to the pathological complexity of the diseased tissue. In addition, AG is usually found to have an MYB-QKI rearrangement on genetic analysis. Due to the small number of reported cases and studies, our understanding and knowledge of this disease are still lacking. The potential malignant changes and prognostic factors need to be verified in more than clinical cases and basic research in the future.

Pediatric angiocentric glioma with acute intracerebral hemorrhage: A case report with 36 months follow-up

Background:

Angiocentric glioma (AG) is an extremely rare intracranial tumor that was first described in 2005 and identified as a special type of intracranial tumor in 2007 by the WHO, which mainly affects children and young adolescents. Epilepsy is the main presentation; therefore, it was recognized as a seizure-related tumor in the past. Here, we report a case of AG with acute intracerebral hemorrhage (ICH) as the first symptom who never had a seizure onset.

Case Description:

A 3-year-old girl with the right limb weakness was admitted to our hospital 4 h after onset in 2018. Computed tomography showed a hematoma of about 20 ml accompanied by a hyper/iso-dense spheroid lesion located in the sub-cortex of the left parietal lobe. Magnetic resonance image (MRI) showed signs of hypointense signal in T1, T2, and fluid-attenuated inversion recovery sequence, distinct enhancement of this tumefactive lesion in the contrast-enhanced sequence. Thus, the admission diagnosis was neoplasm with acute ICH. A gross total resection of the tumor was achieved by parietal craniotomy. The histopathological diagnosis was AG. No signs showed tumor recurrence after 36 months of follow-up.

Conclusion:

This is the sole case of AGs with acute intracranial hemorrhage as the first symptom without any kind of epilepsy by far. This case had unique MRI signs that were different from the previous description. This case enriches the clinical and radiological manifestations of AG and reveals that further investigations are needed to further understand AG.

Cystic angiocentric glioma: a case report and literature review

Angiocentric glioma (AG) is a rare form of brain tumor characterized by cortical epileptogenic lesions that show angiocentric patterns upon histopathological examination. Cystoid degeneration is a rare radiological manifestation of this condition. We report a case involving the left eloquent cortical areas and review the clinical features of angiocentric glioma. A 10-year-old girl presented with a history of refractory drug-resistant epilepsy. Imaging revealed a cystic-solid neoplasm within the left frontal lobe. Surgical procedures were performed, and it was observed that the pathological manifestations were consistent with those of AG. Angiocentric glioma should be considered for diagnosis when the supratentorial cortical neoplasm contains a cystic component. The diagnosis of AG can be confirmed by histopathological examination. Gross total resection is the recommended strategy for controlling seizures elicited by this condition.

Angiocentric glioma of brainstem

Angiocentric glioma is a rare brain tumor commonly found in frontal or temporal lobes. It has a benign course, and surgical resection can be curative. Brainstem location is extremely rare, with only six cases reported so far in the literature. In the present study, the seventh case of brainstem angiocentric glioma has been reported, and its course in comparison with supratentorial location and the role of molecular diagnosis has been discussed.

An Update on Pediatric Gliomas

Pediatric gliomas are biologically distinct from adult gliomas. Although recent literature uncovered new genetic alterations, the prognostic implications of these discoveries are still unclear. This article provides an update on the histologic and molecular features with prognostic and/or therapeutic implications in pediatric gliomas.

Angiocentric glioma-associated seizures: The possible role of EATT2, pyruvate carboxylase and glutamine synthetase

PURPOSE

Our purpose was to better understand the pathogenesis of seizures associated with angiocentric glioma. Angiocentric glioma is an indolent and rare low-grade glioma. Its typical clinical presentation is with epileptic seizures. The pathogenesis of tumor-associated seizures is poorly understood. Among the possible pathomechanisms, the increased neurotoxic concentrations of the glutamate has been proposed. Glutamate transporters, pyruvate carboxylase and glutamine synthetase are involved in maintaining the physiological concentration of glutamate in the inter synaptic spaces.

METHODS

We evaluated the immunohistochemical expression of EAAT2 (the most important glutamate transporter), pyruvate carboxylase and glutamine synthetase in 17 angiocentric gliomas.

RESULTS

EAAT2 was never expressed (0%) in the neoplastic cells in none of the cases studied. Pyruvate carboxylase was expressed in the cytoplasm of the neoplastic cells in 16/17 cases (94 %). Glutamine synthetase was expressed in the cytoplasm of the neoplastic cells in 15/17 cases (88 %).

CONCLUSION

The net result of this enzymatic expression, in particular considering the loss of EAAT2, could be an increased glutamate concentration in the synaptic clef, which might increase local network excitability initially involving intratumoral neurons. The observation that the angiocentric glioma-associated epilepsy might be at least in part related to EAAT2 deficiency opens up interesting therapeutic perspectives.

[Neuropathology of epilepsy]

The neuropathology of epilepsy aims at diagnosing the cerebral lesions underlying epilepsy that are obtained from epilepsy surgery, or rarely from biopsy or autopsy. The main histopathological and immunohistochemical characteristics of several entities are described: epilepsy-associated hippocampal sclerosis, long-term epilepsy-associated tumours, cortical malformations, vascular malformations, glial scars, encephalitides, and focal neuronal lipofuscinosis. The diagnostic approach, the differential diagnosis and the histochemical and immunohistochemical tools are detailed in order to provide the pathologist with a summarized toolkit to handle the broad range of epileptogenic lesions.

Clinical characteristics, treatment and prognosis of angiocentric glioma

Angiocentric glioma (AG) is a rare subtype of neuroepithelial tumor in children and young adults that commonly presents with seizures. To study the clinical characteristics, treatment and prognosis of patients with AG, the features of two cases of AG were described and 108 cases reported in the literature were assessed. The cases of the present study were two males aged 8 and 16 years, who mainly presented with seizures. MRI revealed superficial, non-enhanced lesions in the left temporal and right frontal lobe, respectively. The two patients underwent gross total resection (GTR) and remained seizure-free without neurological deficits after 3.5 and 2.5 years, respectively. Histopathological examination revealed that the tumors consisted of monomorphous cells that surrounded the blood vessels and neurons in the cerebral cortex, and formed concentric sleeves or pseudorosettes. Furthermore, immunostaining indicated that the diffuse infiltrative neoplastic cells were positive for glial fibrillary acidic protein and a dot-like pattern of epithelial membrane antigen was observed. AG mostly appeared similar to low-grade gliomas on MRI. GTR of the lesions was curative and radiation or chemotherapy were not required. AG typically has a favorable prognosis, with low mortality and incidence of disability.

Low-grade developmental and epilepsy associated brain tumors: a critical update 2020

Brain tumors represent the second most frequent etiology in patients with focal seizure onset before 18 years of age and submitted to epilepsy surgery. Hence, this category of brain tumors, herein defined as low-grade, developmental, epilepsy-associated brain tumors (LEAT) is different from those frequently encountered in adults as (A): 77% of LEAT occur in the temporal lobe; (B): the vast majority of LEAT are of low malignancy and classified as WHO I°; (C): LEAT are often composed of mixed glial and neuronal cell components and present with variable growth patterns including small cysts or nodules; (D): LEAT do not share common gene driving mutations, such as IDH1 or 1p/19q co-deletions. Characteristic entities comprise the ganglioglioma (GG), the dysembryoplastic neuroepithelial tumor (DNT), the angiocentric glioma (AG), the isomorphic diffuse glioma (IDG) and the papillary glio-neuronal tumor (PGNT), representing 73.2% of 1680 tumors collected in a large German series of 6747 patients submitted to epilepsy surgery. In the realm of exciting discoveries of genetic drivers of brain tumors new genes have been also reported for LEAT. BRAF V600E mutations were linked to GG with CD34 expression, FGFR1 mutations to DNT, MYB alterations to AG and also IDG and PRKCA fusions to PGNT, suggesting the possibility to also develop a genetically driven tumor classification scheme for LEAT. Rare availability of LEAT in a single center is a challenging obstacle, however, to systematically unravel the neurobiological nature and clinical behavior of LEAT. Other challenges in need of clarification include malignant tumor progression of LEAT entities, seizure relapse in patients following bulk tumor resection and the controversial issue of associated focal cortical dysplasia as additional pathomechanism. In order to advance our understanding and promote reliable diagnostic work-up of LEAT, we recommend, therefore, international collaboration to achieve our goals.

Temporal lobe angiocentric glioma with oligodendroglioma-like areas: a rare association of an uncommon tumor. A case report with review of literature

BACKGROUND

Angiocentric glioma (AG) is a relatively uncommon clinico-pathological entity that presents in childhood. Angiocentric glioma displays various histopathological features which resemble cortical ependymoma, astroblastoma, and pilomyxoid astrocytoma and schwannoma. The astrocytes in angiocentric glioma appear peculiarly elongated, bipolar in shape, and characteristically arranged around blood vessels. They resemble radial glia and tanycytes morphologically. Unlike ependymomas, AG is a diffusely infiltrating lesion and perivascular processes are often much thicker than those in classic ependymomas.

CASE PRESENTATION

AG usually present clinically as seizures, often as medically intractable epilepsy. In the indexed case, apart from unusual presentation with features of raised intra-cranial tension, an unusual histological picture of a more cellular oligodendroglioma like component was also seen.

CONCLUSION

The appropriate diagnosis is critical as AG is usually slowly growing and treatable by surgical excision alone.

Angiocentric glioma: Drop Metastases to the Spinal Cord

BACKGROUND

Angiocentric glioma (AG) is an epileptogenic low grade (World Health Organization grade I) glial tumor with astrocytic and ependymal differentiation, most commonly affecting the pediatric and adolescent population. Despite its infiltrating histological growth kinetics, it is widely accepted that AG has a low potential for aggressive behavior.

CASE DESCRIPTION

We present the case of a 42-year-old man who represents the first documented case of not only extracranial manifestation of AG, but also spinal metastatic dissemination. Our patient initially presented with a generalized tonic clonic seizure; following a biopsy, he was diagnosed with a low-grade supratentorial astrocytoma and subsequently received fractionated radiotherapy. He presented 10 months later with worsening dorsal column symptoms and was found to have a contrast-enhancing intradural extramedullary lesion that was surgically resected and histologically confirmed as an AG.

CONCLUSION

Further research is required to examine the microenvironment and potential for malignant change in this tumor.

Angiocentric glioma mimicking encephalomalacia

Angiocentric glioma is a rare low-grade neoplasm of the central nervous system which typically presents with medication-refractory seizures in children and young adults. On magnetic resonance imaging, angiocentric glioma is classically T1 hypointense and T2/FLAIR hyperintense. We present the case of a 40-year-old male who had been followed by our institution for 17 years for management of epilepsy. Initial and repeat brain imaging showed an apparent region of cystic encephalomalacia in the right frontal lobe. In an attempt to control his seizures, the lesion was resected. Grossly, the cut surface of the specimen was characterized by multiple small cystic spaces. Microscopically, the lesion was composed of an infiltrative population of glial cells variably arranged in perivascular “pseudorosettes,” nodules, and subpial “palisades.” The final diagnosis was angiocentric glioma. This is the second reported case of an angiocentric glioma mistaken for encephalomalacia.

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.

Angiocentric Glioma: Report of a Rare Case Presenting with Psychosis

Angiocentric glioma (AG), first described in 2005, was included as a distinct entity in the 2007 World Health Organization Classification of Tumors of the Central Nervous System. It is a very rare cerebrocortical tumor mainly affecting children and young adults with a history of intractable partial seizures. The histopathological features of this entity are perivascular arrangement of monomorphic, bipolar spindled cells with subpial aggregation of tumor cells and variable neuroparenchymal colonization. Of uncertain histogenesis, this is a stable/slowly growing tumor. Prognosis following total surgical resection is favorable. We describe an AG in a 16-year-old, intellectually disabled, male patient, with psychosis. This is a rare presentation with only one such case in literature. Patient's symptoms ameliorated following surgery.

A malignant astrocytoma with uncommon angiocentric features and dot-like EMA expression

Angiocentric features are uncommon in high-grade World Health Organisation (WHO) brain tumours, whilst they are typical for WHO grade I tumours, e.g. angiocentric gliomas. We present an unusual glial tumour that occurred in a 59-year-old man. The tumour had equivocal radiologic and histopathologic features, especially a characteristic angiocentric pattern, low-to-moderate Ki67, and dot-like epithelial membrane antigen expression. The tumour did not show features characteristic for glioblastoma; however, it recurred as glioblastoma four months later. Based on this case, we show that high-grade WHO brain tumours may show an angiocentric pattern typical for low-grade WHO brain tumours, such as angiocentric gliomas.

Brainstem angiocentric glioma: report of 2 cases

Angiocentric glioma is a rare tumor that was recognized by the WHO Classification of Tumours of the Central Nervous System as a distinct clinicopathological entity in 2007. Since this initial description, the vast majority of cases of angiocentric glioma reported in the literature have involved tumors of the cerebral hemispheres. To date, only 1 case of angiocentric glioma arising from the posterior midbrain has been reported. The authors present the cases of 2 pediatric patients who were found to have brainstem angiocentric gliomas. The clinical course, radiological and pathological features, treatment, and follow-up are described. The first case is one of a 5-year-old girl who presented with double vision, headache, and nausea and was found to have a midbrain lesion with pathological features consistent with angiocentric glioma. She was treated with resection and endoscopic third ventriculostomy (ETV), followed by close observation and serial neuroimaging. The second case is one of a 6-year-old boy who presented with progressive mouth drooping and problems with balance. He was found to have a pontine lesion with pathological features consistent with angiocentric glioma. This patient was treated with ETV, followed by close observation and serial neuroimaging. This report includes 6 and 1.5 years of follow-up of the patients, respectively. While there are limited data regarding the prognosis or long-term management of patients with brainstem angiocentric gliomas, the cases described in this report suggest an indolent course for this tumor, similar to the course of angiocentric gliomas located in the cerebral hemispheres.

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

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

Low-grade epilepsy-associated neuroepithelial tumours - the 2016 WHO classification

Rapid developments in molecular genetic technology and research have swiftly advanced our understanding of neuro-oncology. As a consequence, the WHO invited their expert panels to revise the current classification system of brain tumours and to introduce, for the first time, a molecular genetic approach for selected tumour entities, thus setting a new gold standard in histopathology. The revised 5th edition of the 'blue book' was released in May 2016 and will have a major impact in stratifying diagnosis and treatment. However, low-grade neuroepithelial tumours that present with early-onset focal epilepsy and are mostly seen in children and young adults (previously designated as long-term epilepsy-associated neuroepithelial tumours, LEAT) lack such innovative clinicopathological and molecular genetic tools. The Neuropathology Task Force of the International League against Epilepsy will critically discuss this issue, and will offer perspectives on how to decipher and validate clinically meaningful LEAT entities using the current WHO approach that integrates clinicopathological and genetic classification systems.

Angiocentric glioma transformed into anaplastic ependymoma: Review of the evidence for malignant potential

Angiocentric glioma (AG) is a low grade glioma, that was first described in 2002. Since this description, 83 patients with AG have been described, including ours. AG typically presents in childhood with medically refractory seizures that are cured with gross surgical resection. Whilst the natural history is that of a benign tumour, there have been reports of recurrence, transformation, and malignant features that suggest that AG is potentially malignant. We add to the literature a case of a 16-year-old girl who presented in May 2011 with a 3-month history of complex partial seizures, with MRI showing a T2-weighted hyperintense lesion in the left insula and inferior frontal lobe. This was confirmed on biopsy as AG and was followed with surveillance imaging. In April 2012, she presented with disease progression and underwent a left temporal lobectomy, with histology showing both AG and grade II astrocytoma. Adjuvant radiotherapy of 50 Gray in 28 fractions was administered. A small area of contrast enhancement appeared in the left parietal lobe in December 2012, which progressed over subsequent months. In June 2013, she underwent a near total excision, with histology showing anaplastic ependymoma. She received six cycles of adjuvant temozolamide. Despite this, the tumour continued to progress, with her seizure control deteriorating, and the development of a right hemiparesis. The patient died in January 2014, aged 19years.

Morphological and molecular features of astroblastoma, including BRAFV600E mutations, suggest an ontological relationship to other cortical-based gliomas of children and young adults

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.

Exploiting molecular biology for diagnosis and targeted management of pediatric low-grade gliomas

The majority of brain tumors arising in children are low-grade gliomas. Although historically categorized together as pediatric low-grade gliomas (PLGGs), there is significant histologic and genetic diversity within this group. In general, prognosis for PLGGs is excellent, and limitation of sequelae from tumor and treatment is paramount. Advances in high-throughput genetic sequencing and gene expression profiling are fundamentally changing the way PLGGs are classified and managed. Here, we review the histologic subtypes and highlight how recent advances in elucidating the molecular pathogenesis of these tumors have refined diagnosis and prognostication. Additionally, we discuss how characterizing specific genetic alterations has paved the way for the rational use of targeted therapies that are currently in various phase clinical trials.

Genetic alterations in uncommon low-grade neuroepithelial tumors: BRAF, FGFR1, and MYB mutations occur at high frequency and align with morphology

Low-grade neuroepithelial tumors (LGNTs) are diverse CNS tumors presenting in children and young adults, often with a history of epilepsy. While the genetic profiles of common LGNTs, such as the pilocytic astrocytoma and 'adult-type' diffuse gliomas, are largely established, those of uncommon LGNTs remain to be defined. In this study, we have used massively parallel sequencing and various targeted molecular genetic approaches to study alterations in 91 LGNTs, mostly from children but including young adult patients. These tumors comprise dysembryoplastic neuroepithelial tumors (DNETs; n = 22), diffuse oligodendroglial tumors (d-OTs; n = 20), diffuse astrocytomas (DAs; n = 17), angiocentric gliomas (n = 15), and gangliogliomas (n = 17). Most LGNTs (84 %) analyzed by whole-genome sequencing (WGS) were characterized by a single driver genetic alteration. Alterations of FGFR1 occurred frequently in LGNTs composed of oligodendrocyte-like cells, being present in 82 % of DNETs and 40 % of d-OTs. In contrast, a MYB-QKI fusion characterized almost all angiocentric gliomas (87 %), and MYB fusion genes were the most common genetic alteration in DAs (41 %). A BRAF:p.V600E mutation was present in 35 % of gangliogliomas and 18 % of DAs. Pathogenic alterations in FGFR1/2/3, BRAF, or MYB/MYBL1 occurred in 78 % of the series. Adult-type d-OTs with an IDH1/2 mutation occurred in four adolescents, the youngest aged 15 years at biopsy. Despite a detailed analysis, novel genetic alterations were limited to two fusion genes, EWSR1-PATZ1 and SLMAP-NTRK2, both in gangliogliomas. Alterations in BRAF, FGFR1, or MYB account for most pathogenic alterations in LGNTs, including pilocytic astrocytomas, and alignment of these genetic alterations and cytologic features across LGNTs has diagnostic implications. Additionally, therapeutic options based upon targeting the effects of these alterations are already in clinical trials.

MYB-QKI rearrangements in angiocentric glioma drive tumorigenicity through a tripartite mechanism

Angiocentric gliomas are pediatric low-grade gliomas (PLGGs) without known recurrent genetic drivers. We performed genomic analysis of new and published data from 249 PLGGs including 19 Angiocentric Gliomas. We identified MYB-QKI fusions as a specific and single candidate driver event in Angiocentric Gliomas. In vitro and in vivo functional studies show MYB-QKI rearrangements promote tumorigenesis through three mechanisms: MYB activation by truncation, enhancer translocation driving aberrant MYB-QKI expression, and hemizygous loss of the tumor suppressor QKI. This represents the first example of a single driver rearrangement simultaneously transforming cells via three genetic and epigenetic mechanisms in a tumor.

Clinical attributes and surgical outcomes of angiocentric gliomas

Angiocentric gliomas (AG) are exceedingly rare low-grade neoplasms which often present in the form of intractable epilepsy within younger patients. The current study extensively reviews all reported cases which were pathologically verified as AG in the literature to analyze clinical attributes and surgical outcomes of this neoplasm. There were 88 patients with AG reported in the literature consisting mostly of pediatric cases. The sex distribution consisted of 45 males and 36 females with the remaining seven cases not documenting sex. The average age of initial diagnosis was 16years with almost half of all diagnosed patients being within the first decade of life. In cases where extent of resection was reported, gross total resection (GTR) was achieved in 54 patients, subtotal resection (STR) in 16, and biopsy only in three. Post-operative complications were transient and only occurred in three patients with no reports of death following surgery. Only five cases reported tumor recurrence on follow-up. Eight patients had seizure recurrence post-operatively and GTR offered improved rates of seizure control when compared to STR (p=0.0005). Nearly half of the cases of AG are diagnosed within the first decade of life and they usually manifest with intractable seizures. GTR appears to offer better seizure control in the post-operative period. Surgical resection is the mainstay therapy for AG as post-operative complications and tumor recurrence remain uncommon. Since the number of reported cases is limited, future studies with longer follow-up periods will help elaborate more long-term outcomes.

Rare glial tumors

This chapter describes the epidemiology, pathology, molecular characteristics, clinical and neuroimaging features, treatment, outcome, and prognostic factors of the rare glial tumors. This category includes subependymal giant cell astrocytoma, pleomorphic xanthoastrocytoma, astroblastoma, chordoid glioma of the third ventricle, angiocentric glioma, ganglioglioma, desmoplastic infantile astrocytoma and ganglioma, dysembryoplastic neuroepithelial tumor, papillary glioneuronal tumor, and rosette-forming glioneuronal tumor of the fourth ventricle. Many of these tumors, in particular glioneuronal tumors, prevail in children and young adults, are characterized by pharmacoresistant seizures, and have an indolent course, and long survival following surgical resection. Radiotherapy and chemotherapy are reserved for recurrent and/or aggressive forms. New molecular alterations are increasingly recognized.

Angiocentric glioma, a recently added WHO grade-I tumor

Angiocentric glioma (AG) is a distinct group of tumors, grade I according to the 2007 WHO classification of tumors of the central nervous system. It is a rare group predominantly seen in children and young adults, with good prognosis following gross total resection. A young child presented with progressively worsening seizure activity; MRI revealed a lesion involving the left posterior frontal lobe. The lesion was surgically resected, and the child is now free of seizure medications, with good neurological function.

Cystoid angiocentric glioma: A case report and literature review

Angiocentric glioma is a rare subtype of neuroepithelial tumor that is associated with a history of epilepsy. We report a case of cystoid angiocentric glioma associated with an area of calcification. This 25 year old male patient presented with tonic clonic spasm. He underwent craniotomy with complete resection of the lesion. Pathologic specimen showed monomorphous bipolar cells with angiocentric growth pattern.

Rapidly Enlarging Pediatric Cortical Ependymoma

We report a 10-year-old boy with supratentorial cortical ependymoma that rapidly grew in the course of 3 years. He suffered generalized seizures when he was 5 years old; MRI showed a small cortical lesion in the right postcentral gyrus. MRI performed 2 years later revealed no changes. For the next 3 years he was free of seizures. However, at the age of 10 he again suffered generalized seizures and MRI disclosed a large parietal tumor. It was resected totally and he remains free of neurological deficits. The histopathological diagnosis was ependymoma. Pediatric supratentorial cortical ependymomas are extremely rare. We recommend including cortical ependymoma as a differential diagnosis in pediatric patients with cortical mass lesions presenting with seizures and careful follow-up even in the absence of symptoms because these tumors may progress.

"Unusual brain stone": heavily calcified primary neoplasm with some features suggestive of angiocentric glioma

This 40-year-old man presented with a 5-month history of progressive right-sided headache associated with visual blurring. He also had a history of epilepsy but had been seizure free with medication for the past 10 years. An initial CT scan of his brain performed 16 years previously had revealed a small area of calcification in the right parietal region. In the current presentation, he had a left-sided homonymous hemianopia but no other neurological deficits. A CT scan of his brain showed a much larger calcified, partly cystic lesion in the right parietal region. Because he was symptomatic, the lesion was excised and the cyst was drained. Histological examination of the excised tissue showed an unusual primary tumor that was difficult to classify but had some features of angiocentric glioma. The heavy calcification, mixed-density cell population, and regions with features of angiocentric glioma were most unusual. The patient remained asymptomatic 5 years after surgery, and follow-up scans did not show recurrence.

Supratentorial cortical ependymoma: An unusual presentation of a rare tumor

Ependymomas are glial tumors derived from ependymal cells lining the ventricles and the central canal of the spinal cord. Two thirds of ependymomas arise in the infratentorial or intraventricles, whereas one-third are located in supratentorial space. But supratentorial "cortical" ependymomas are very rare. We report a case of a cortical ependymoma in a 17-year-old boy. The patient presented with transient recurrent right weakness and diplopia. This tumor was located in the left parieto-occipital region and he had gross total excision. Microscopy and immunohistochemistry showed grade III differentiation ependymoma.