Central Nervous System Tumors With Ependymal Features: A Broadened Spectrum of Primarily Ependymal Differentiation?

Human Patient-Derived Brain Tumor Models to Recapitulate Ependymoma Tumor Vasculature

Despite in vivo malignancy, ependymoma lacks cell culture models, thus limiting therapy development. Here, we used a tunable three-dimensional (3D) culture system to approximate the ependymoma microenvironment for recapitulating a patient's tumor in vitro. Our data showed that the inclusion of VEGF in serum-free, mixed neural and endothelial cell culture media supported the in vitro growth of all four ependymoma patient samples. The growth was driven by Nestin and Ki67 double-positive cells in a putative cancer stem cell niche, which was manifested as rosette-looking clusters in 2D and spheroids in 3D. The effects of extracellular matrix (ECM) such as collagen or Matrigel superseded that of the media conditions, with Matrigel resulting in the greater enrichment of Nestin-positive cells. When mixed with endothelial cells, the 3D co-culture models developed capillary networks resembling the in vivo ependymoma vasculature. The transcriptomic analysis of two patient cases demonstrated the separation of in vitro cultures by individual patients, with one patient's culture samples closely clustered with the primary tumor tissue. While VEGF was found to be necessary for preserving the transcriptomic features of in vitro cultures, the presence of endothelial cells shifted the gene's expression patterns, especially genes associated with ECM remodeling. The homeobox genes were mostly affected in the 3D in vitro models compared to the primary tumor tissue and between different 3D formats. These findings provide a basis for understanding the ependymoma microenvironment and enabling the further development of patient-derived in vitro ependymoma models for personalized medicine.

Early ependymal tumor with MN1-BEND2 fusion: a mostly cerebral tumor of female children with a good prognosis that is distinct from classical astroblastoma

PURPOSE

Review of the clinicopathologic and genetic features of early ependymal tumor with MN1-BEND2 fusion (EET MN1-BEND2), classical astroblastomas, and recently described related pediatric CNS tumors. I also briefly review general mechanisms of gene expression silencing by DNA methylation and chromatin remodeling, and genomic DNA methylation profiling as a powerful new tool for CNS tumor classification.

METHODS

Literature review and illustration of tumor histopathologic features and prenatal gene expression timelines.

RESULTS

Astroblastoma, originally descried by Bailey and Cushing in 1926, has been an enigmatic tumor. Whether they are of ependymal or astrocytic derivation was argued for decades. Recent genetic evidence supports existence of both ependymal and astrocytic astroblastoma-like tumors. Studies have shown that tumors exhibiting astroblastoma-like histology can be classified into discrete entities based on their genomic DNA methylation profiles, gene expression, and in some cases, the presence of unique gene fusions. One such tumor, EET MN1-BEND2 occurs mostly in female children, and has an overall very good prognosis with surgical management. It contains a gene fusion comprised of portions of the MN1 gene at chromosomal location 22q12.1 and the BEND2 gene at Xp22.13. Other emerging pediatric CNS tumor entities demonstrating ependymal or astroblastoma-like histological features also harbor gene fusions involving chromosome X, 11q22 and 22q12 breakpoint regions.

CONCLUSIONS

Genomic DNA profiling has facilitated discovery of several new CNS tumor entities, however, traditional methods, such as immunohistochemistry, DNA or RNA sequencing, and cytogenetic studies, including fluorescence in situ hybridization, remain necessary for their accurate biological classification and diagnosis.

Clinicoradiological and histopathological characteristics and treatment outcomes of cerebral astroblastoma in children: a single-institution experience

OBJECTIVE

Astroblastoma (AB) is a rare glial tumor. The optimal treatment and prognosis of this tumor remain unclear. The authors retrospectively analyzed the clinical characteristics, neuroimaging findings, histopathological results, and treatment outcomes of 7 patients with AB.

METHODS

The study comprised 7 patients with pathologically proven AB who were surgically treated at Samsung Medical Center from November 1994 to January 2019. Clinicoradiological, histopathological, and surgical records were reviewed.

RESULTS

The patients included 5 girls (71.4%) and 2 boys (28.6%), with a median age of 13 years. All patients showed contrast enhancement on preoperative MRI: 5 ABs (71.4%) showed a concomitant solid and cystic appearance, and 2 (28.6%) demonstrated a solid appearance. ABs in 6 patients (85.7%) showed a well-circumscribed, characteristic "bubbly" appearance on T2-weighted MRI. Gross-total resection (GTR) was achieved in all cases (100%). Six patients (85.7%) were diagnosed with high-grade AB and 1 (14.3%) with low-grade AB. Six (85.7%) of the 7 patients received adjuvant treatment after resection, including 5 (83.3%) with AB who received chemotherapy and radiotherapy and 1 (16.7%) who received proton therapy alone. The median clinical follow-up duration was 96 months (range 48-189 months). Two patients experienced recurrence, and all patients in this series were alive at the last follow-up.

CONCLUSIONS

In this study, the clinicoradiological and histopathological features of AB were described. Based on the authors' limited experience with 7 cases, resection with the goal of GTR is currently the mainstream treatment for AB, and adjuvant radiation treatment should be considered after surgery.

Ependymoma-like tumor with mesenchymal differentiation harboring C11orf95-NCOA1/2 or -RELA fusion: A hitherto unclassified tumor related to ependymoma

Recurrent fusion genes involving C11orf95, C11orf95‐RELA, have been identified only in supratentorial ependymomas among primary CNS tumors. Here, we report hitherto histopathologically unclassifiable high‐grade tumors, under the tentative label of “ependymoma‐like tumors with mesenchymal differentiation (ELTMDs),” harboring C11orf95‐NCOA1/2 or ‐RELA fusion. We examined the clinicopathological and molecular features in five cases of ELTMDs. Except for one adult case (50 years old), all cases were in children ranging from 1 to 2.5 years old. All patients presented with a mass lesion in the cerebral hemisphere. Histologically, all cases demonstrated a similar histology with a mixture of components. The major components were embryonal‐appearing components forming well‐delineated tumor cell nests composed of small uniform cells with high proliferative activity, and spindle‐cell mesenchymal components with a low‐ to high‐grade sarcoma‐like appearance. The embryonal‐appearing components exhibited minimal ependymal differentiation including a characteristic EMA positivity and tubular structures, but histologically did not fit with ependymoma because they lacked perivascular pseudorosettes, a histological hallmark of ependymoma, formed well‐delineated nests, and had diffuse and strong staining for CAM5.2. Molecular analysis identified C11orf95‐NCOA1, ‐NCOA2, and ‐RELA in two, one, and two cases, respectively. t‐distributed stochastic neighbor embedding analysis of DNA methylation data from two cases with C11orf95‐NCOA1 or ‐NCOA2 and a reference set of 380 CNS tumors revealed that these two cases were clustered together and were distinct from all subgroups of ependymomas. In conclusion, although ELTMDs exhibited morphological and genetic associations with supratentorial ependymoma with C11orf95‐RELA, they cannot be regarded as ependymoma. Further analyses of more cases are needed to clarify their differences and similarities.

The Effects of Surgery and Adjuvant Therapy on Survival Outcomes in Clear Cell Ependymomas: A Systematic Review and Meta-Analysis of Individual Patient Data

BACKGROUND

The survival outcomes of clear cell ependymomas are poorly understood. This study clarifies the role of surgery and adjuvant therapy when this morphologically distinct tumor is encountered.

METHODS

A systematic search for studies relating to clear cell ependymomas was conducted. Primary outcomes were progression-free survival and overall survival. Prognostic variables were age, sex, tumor consistency, extent of resection, and postoperative adjuvant therapy. Kaplan-Meier survival curves were generated and compared by the log-rank test. Multivariate Cox regression models were constructed, interrogated with Schoenfeld residuals, and used to identify independent prognostic factors.

RESULTS

Of the 384 articles retrieved, 8 articles comprising 77 cases of clear cell ependymoma were included. Five-year overall survival and progression-free survival were 58.1% (95% confidence interval [CI], 46.3%-72.9%) and 46.3% (95% CI, 34.2%-62.8%), respectively. Kaplan-Meier analysis with the log-rank test showed that gross total resection was superior to subtotal resection in prolonging survival (P = 0.047) and delayed time to recurrence (P < 0.01). Multivariate analysis confirmed gross total resection as an independent protective factor against relapse (odds ratio, 0.39; 95% CI, 0.17-0.89; P = 0.03). Age <50 years predicted longer overall survival (odds ratio, 0.16; 95% CI, 0.05-0.49; P < 0.01). Postoperative adjuvant therapy after gross total resection did not affect overall survival (P = 0.98) or progression-free survival (P = 0.93). Adjuvant therapy after subtotal resection favored improved overall survival (P = 0.052).

CONCLUSIONS

Clear cell ependymomas are particularly aggressive in those aged >50 years. Gross total resection remains the cornerstone of management. Postoperative adjuvant therapy is likely to be of survival benefit only after subtotal resection.

Role of DNA Methylation Profile in Diagnosing Astroblastoma: A Case Report and Literature Review

Astroblastoma is a rare tumor of the central nervous system (CNS) with uncertain clinical behavior. Recently, DNA methylation profiling has been shown to provide a highly robust and reproducible approach for the classification of all CNS tumors across different age groups. By using DNA methylation profiling, a subset of CNS high-grade tumors with astroblastoma-like morphology characterized by the meningioma 1 gene (MN1) rearrangements, has been identified; they were termed “CNS high-grade neuroepithelial tumors with MN1 alteration” (CNS-HGNET-MN1). Here, we describe a case of CNS-HGNET-MN1 diagnosed by DNA methylation profiling, using Illumina Infinium HumanMethylationEPIC BeadChip (EPIC), that offers the opportunity to conduct a brief literature review. The patient presented with an episode of partial seizures involving the right hemisoma. A gross total resection was performed. No other treatment was proposed in light of the histological and molecular findings. After 21 months, the patient is disease-free in good clinical conditions. Also in view of this case, we recommend DNA-methylation profiling as an important tool for diagnosis and more effective patient stratification and management.

Updates in the Neuoroimaging and WHO Classification of Primary CNS Gliomas: A Review of Current Terminology, Diagnosis, and Clinical Relevance From a Radiologic Prospective

As new advances in the genomics and imaging of CNS tumors continues to evolve, a standardized system for classification is increasingly essential to diagnosis and management. The molecular markers introduced in the 2016 WHO classification of CNS tumors bring both practical and conceptual advances to the characterization of gliomas, strengthening the prognostic and predictive value of terminology while shedding light on the underlying mechanisms that drive biologic behavior. The purpose of this article is to provide a succinct overview of primary intracranial gliomas from a neuroradiologic prospective and according to the 5th edition WHO classification that was revised in 2016. An update of the molecular markers pertinent to defining the major lineages of brain gliomas will be provided, followed by discussion of the terminology, grading and imaging features associated with individual entities. Neuroradiologists should be aware of the key genomic and radiomic features of common brain gliomas, and familiar with an integrated approach to their diagnosis and grading.

Genomic analysis demonstrates that histologically-defined astroblastomas are molecularly heterogeneous and that tumors with MN1 rearrangement exhibit the most favorable prognosis

Astroblastoma (AB) is a rare CNS tumor demonstrating abundant astroblastomatous pseudorosettes. Its molecular features have not been comprehensively studied and its status as a tumor entity is controversial. We analyzed a cohort of 27 histologically-defined ABs using DNA methylation profiling, copy number analysis, FISH and site-directed sequencing. Most cases demonstrated mutually exclusive MN1 rearrangements (n = 10) or BRAF^V600E mutations (n = 7). Two additional cases harbored RELA rearrangements. Other cases lacked these specific genetic alterations (n = 8). By DNA methylation profiling, tumors with MN1 or RELA rearrangement clustered with high-grade neuroepithelial tumor with MN1 alteration (HGNET-MN1) and RELA-fusion ependymoma, respectively. In contrast, BRAF^V600E-mutant tumors grouped with pleomorphic xanthoastrocytoma (PXA). Six additional tumors clustered with either supratentorial pilocytic astrocytoma and ganglioglioma (LGG-PA/GG-ST), normal or reactive cerebrum, or with no defined DNA methylation class. While certain histologic features favored one genetic group over another, no group could be reliably distinguished by histopathology alone. Survival analysis between genetic AB subtypes was limited by sample size, but showed that MN1-rearranged AB tumors were characterized by better overall survival compared to other genetic subtypes, in fact, significantly better than BRAF^V600E-mutant tumors (P = 0.013). Our data confirm that histologically-defined ABs are molecularly heterogeneous and do not represent a single entity. They rather encompass several low- to higher-grade glial tumors including neuroepithelial tumors with MN1 rearrangement, PXA-like tumors, RELA ependymomas, and possibly yet uncharacterized lesions. Genetic subtyping of tumors exhibiting AB histology, particularly determination of MN1 and BRAF^V600E status, is necessary for important prognostic and possible treatment implications.

Magnetic resonance spectroscopy in posterior fossa tumours: the tumour spectroscopic signature may improve discrimination in adults among haemangioblastoma, ependymal tumours, medulloblastoma, and metastasis

OBJECTIVES

Assessing a posterior fossa tumour in an adult can be challenging. Metastasis, haemangioblastoma, ependymal tumours, and medulloblastoma are the most common diagnostic possibilities. Our aim was to evaluate the contribution of magnetic resonance spectroscopy (MRS) in the diagnosis of these entities.

METHODS

We retrospectively evaluated 56 consecutive patients with a posterior fossa tumour and histological diagnosis of ependymal tumour, medulloblastoma, haemangioblastoma, and metastasis in which good-quality spectra at short (TE 30 ms) or/and intermediate (TE, 136 ms) TE were available. Spectra were compared using the Mann-Whitney U non-parametric test in order to select the spectral datapoints and the intensity ratios that showed significant differences between groups of lesions. Performance of these datapoints and their ratios were assessed with ROC curves.

RESULTS

The most characteristic signatures on spectroscopy were high choline (Cho) in medulloblastoma (p < 0.001), high myoinositol (mIns) in ependymal tumours (p < 0.05), and high lipids (LIP) in haemangioblastoma (p < 0.01) and metastasis (p < 0.01). Selected ratios between normalised intensity signals of resonances provided accuracy values between 79 and 95% for pairwise comparisons. Intensity ratio NI_{3.21ppm/3.55ppm} provided satisfactory discrimination between medulloblastoma and ependymal tumours (accuracy, 92%), ratio NI_{2.11ppm/1.10ppm} discriminated ependymal tumours from haemangioblastoma (accuracy, 94%), ratio NI_{3.21ppm/1.13ppm} discriminated haemangioblastoma from medulloblastoma (accuracy, 95%), and ratio NI_{1.28ppm/2.02pmm} discriminated haemangioblastoma from metastasis (accuracy, 83%).

CONCLUSIONS

MRS may improve the non-invasive diagnosis of posterior fossa tumours in adults.

KEY POINTS

• High choline suggests a medulloblastoma in a posterior fossa tumour. • High myoinositol suggests an ependymal lesion in a posterior fossa tumour. • High lipids suggest a metastasis or a haemangioblastoma in a posterior fossa tumour.

Posterior fossa choroid plexus papilloma with focal ependymal differentiation in an adult patient: A case report and literature review

Choroid plexus papillomas (CPPs) are rare neoplasms classified as World Health Organization grade I tumors. CPPs containing other tissues have occasionally been documented in the literature. However, few of these previous reports have provided clinical and radiological information. We herein report a case of a posterior fossa CPP with focal ependymal differentiation in a 42-year-old woman who presented with a 6-month history of progressive headache. Preoperative radiological images showed a hypervascular tumor protruding into the left foramen of Luschka with perilesional edema. Gross total resection of the tumor was performed. Histopathological examination revealed that the tumor was composed of papillary structures. Immunohistochemical staining of glial fibrillary acidic protein was focally positive around the capillaries, which was suggestive of “perivascular pseudorosette” formation. Our case showed similar imaging appearances as those of CPP; thus, it seems difficult to distinguish CPP with versus without ependymal differentiation by clinical and radiological features alone. The clinical significance and pathogenesis of ependymal differentiation in CPP remain unclear, and further case reports are required.

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.

Multimodal molecular analysis of astroblastoma enables reclassification of most cases into more specific molecular entities

Astroblastoma is a rare and controversial glioma with variable clinical behavior. The diagnosis currently rests on histologic findings of a circumscribed glioma with astroblastomatous pseudorosettes and vascular hyalinization. Immunohistochemical studies have suggested different oncogenic drivers, such as BRAF p.V600E, but very few cases have been studied using genome-wide methodologies. Recent genomic profiling identified a subset of CNS embryonal tumors with astroblastoma-like morphology that harbored MN1 gene fusions, termed "CNS high-grade neuroepithelial tumors with MN1 alteration" (CNS-HGNET-MN1). To further characterize the genetic alterations that drive astroblastomas, we performed targeted next-generation sequencing (NGS) of 500 cancer-associated genes in a series of eight cases. We correlated these findings with break-apart fluorescence in situ hybridization (FISH) analysis of the MN1 locus and genome-wide DNA methylation profiling. Four cases showed MN1 alteration by FISH, including two pediatric cases that lacked other pathogenic alterations, and two adult cases that harbored other cancer-associated gene mutations or copy number alterations (eg, CDKN2A/B homozygous deletion, TP53, ATM and TERT promoter mutations). Three of these cases grouped with the CNS-HGNET-MN1 entity by methylation profiling. Two of four MN1 intact cases by FISH showed genetic features of either anaplastic pleomorphic xanthoastrocytoma (BRAF p.V600E mutation, CDKN2A/B homozygous deletion and TERT promoter mutation) or IDH-wildtype glioblastoma (trisomy 7, monosomy 10, CDK4 amplification and TP53, NRAS and TERT promoter mutations) and these cases had an aggressive clinical course. Two clinically indolent cases remained unclassifiable despite multimodal molecular analysis. We conclude that astroblastoma histology is not specific for any entity including CNS-HGNET-MN1, and that additional genetic characterization should be considered for astroblastomas, as a number of these tumors likely contain a methylation profile or genetic alterations that suggest classification as other tumor entities. Our heterogeneous molecular findings help to explain the clinical unpredictability of astroblastoma.

Decreased FOXJ1 expression and its ciliogenesis programme in aggressive ependymoma and choroid plexus tumours

Well-differentiated human cancers share transcriptional programmes with the normal tissue counterparts from which they arise. These programmes broadly influence cell behaviour and function and are integral modulators of malignancy. Here, we show that the master regulator of motile ciliogenesis, FOXJ1, is highly expressed in cells along the ventricular surface of the human brain. Strong expression is present in cells of the ependyma and the choroid plexus as well as in a subset of cells residing in the subventricular zone. Expression of FOXJ1 and its transcriptional programme is maintained in many well-differentiated human tumours that arise along the ventricle, including low-grade ependymal tumours and choroid plexus papillomas. Anaplastic ependymomas as well as choroid plexus carcinomas show decreased FOXJ1 expression and its associated ciliogenesis programme genes. In ependymomas and choroid plexus tumours, reduced expression of FOXJ1 and its ciliogenesis programme are markers of poor outcome and are therefore useful biomarkers for assessing these tumours. Transitions in ciliogenesis define distinct differentiation states in ependymal and choroid plexus tumours with important implications for patient care. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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.

NHERF1/EBP50 and NF2 as diagnostic markers for choroid plexus tumors

The adaptor protein NHERF1 (Na/H exchanger-3 regulatory factor-1) and its associated ezrin-radixin-moesin-merlin/neurofibromin-2 (ERM-NF2) family proteins are required for epithelial morphogenesis and have been implicated in cancer progression. NHERF1 is expressed in ependymal cells and constitutes a highly sensitive diagnostic marker for ependymoma, where it labels membrane polarity structures. Since NHERF1 and ERM-NF2 proteins show polarized expression in choroid plexus (CP) cells, we tested their diagnostic utility in CP neoplasms. NHERF1 immunohistochemistry in 43 adult and pediatric tumors with papillary morphology revealed strong apical plasma membrane staining in CP papilloma (WHO grade I) and cytoplasmic expression in CP carcinoma (WHO grade III). Ezrin and moesin showed similar but less distinctive staining. NHERF1 also labeled papillary tumors of the pineal region in a microlumen and focal apical membrane pattern, suggestive of a transitional morphology between CP papilloma and ependymoma. CP tumors of all grades could be differentiated from metastatic carcinomas with papillary architecture by NF2, which showed polarized membranous staining in CP tumors. NHERF1 and NF2 immunohistochemistry showed enhanced sensitivity and specificity for CP tumors compared to commonly used markers, including cytokeratins and Kir7.1, emerging as reliable diagnostic tools for the differential diagnosis of papillary tumors of the central nervous system.

A mixed choroid plexus papilloma and ependymoma

We report a novel case of a mixed choroid plexus papilloma (CPP) and ependymoma with cartilaginous differentiation. This kind of mixed tumor has not been previously reported in the English literature. The patient was a 5-year-old girl, who presented with a 1-week history of fever and numbness of the right lower limb. Magnetic resonance imaging of the brain with gadolinium revealed a heterogeneously enhancing mass in the occipital horn of the left lateral ventricle. Histologically, the tumor showed an intermixed CPP area and a low-grade papillary ependymoma-like area, which was studded with cartilage islands and psammoma bodies. In many foci, direct transition of CPP and ependymoma was observed, but there were no high-grade features. We report this novel case, describe the unique microscopic and immunohistochemical features, and speculate on the pathogenesis.

Primary Meningeal Pleomorphic Xanthoastrocytoma With Anaplastic Features: A Report of 2 Cases, One With BRAF(V600E) Mutation and Clinical Response to the BRAF Inhibitor Dabrafenib

Primary meningeal gliomas are rare tumors composed of a heterogeneous group of neoplasms. We present 2 clinically aggressive cases of primary meningeal pleomorphic xanthoastrocytoma that clinically mimicked meningioma. One case presented in the posterior fossa of a 56-year-old woman; the other centered on the left operculum of a 35-year-old woman. These cases showed many of the classic features of pleomorphic xanthoastrocytoma, except that xanthomatous cells were rare and eosinophilic granular bodies were inconspicuous. Both cases exhibited high proliferative indices and superficially invaded the brain. One case harboring a BRAF mutation disseminated to the thecal sac and showed a clinical response to the targeted BRAF inhibitor dabrafenib. These cases seem to represent an unusual primarily extra-axial presentation of pleomorphic xanthoastrocytoma and may account for at least some of the previously reported cases of primary meningeal glioma and/or glial fibrillary acidic protein-immunoreactive meningioma variants. We suggest that BRAF mutation analysis be considered in all meningeal lesions showing atypical histologic or immunohistochemical profiles, particularly those exhibiting glial differentiation, as a diagnostic aid and possible indication for targeted therapy.

Long-term cure of high-grade spinal cord glioma in a pediatric patient who underwent cordectomy

High-grade spinal cord gliomas are rare and carry a poor prognosis. A number of treatment modalities exist for spinal cord gliomas, but no consensus exists regarding their management. Cordectomy represents a possible option for treating these lesions; however, few cases have been reported in adults, and none have been reported in the pediatric population. The authors describe the use of cordectomy for the treatment of a high-grade spinal glioma in a 9-year-old boy who remains cancer free 14 years following his initial presentation.

Papillary Tumor of the Pineal Region: A Distinct Molecular Entity

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.

Pure cortical ependymoma: A rare entity

Ependymomas are mostly infratentorial, intraventricular tumor, accounting for 2–9% of all central nervous system tumors. Supratentorial pure cortical ependymoma are extremely rare tumor with definite ependymal morphology and uncertain histogenesis. They are mostly low grade tumor and are cured with resection, rendering them favorable prognosis. Our case is of 14-year-old female presenting with headache and convulsion of short duration. She underwent gross total excision of the tumor without radiation therapy and her follow-up is uneventful.

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.

Intractable epilepsy due to angiocentric glioma: A case report and minireview

The aim of this case report and minireview was to investigate the diagnosis of and therapeutic approaches for angiocentric glioma (AG) and to summarize the clinical manifestations and the pathological and imaging characteristics of the disease. Intraoperative cortical electroencephalogram (ECoG) monitoring was performed to locate the epileptic foci in a child with AG who presented with intractable epilepsy, prior to the total resection of the tumor being performed under the microscope. The clinical features, imaging characteristics, intraoperative conditions, surgical methods and pathological results were analyzed and compared with the literature. The review revealed that to date, the clinical features of the 52 reported cases of AG (including this case) have been mainly characterized by epilepsy. High T2-weighted image (WI) and fluid-attenuated inversion recovery (FLAIR) signals may be detected with magnetic resonance imaging (MRI) scanning of the cranium; however, no enhancement signals are detected by enhanced scanning. The prognosis following surgical resection is favorable. The lesions in the present case demonstrated clear boundaries with a central cystic affection accompanied by an arachnoid cyst on the left temporal pole. Pathological examination revealed that the lesion was positive for glial fibrillary acidic protein (GFAP), S-100 protein, vimentin, epithelial membrane antigen (EMA), cluster of differentiation 99 (CD99) and D2-40. The Ki-67/MIBk-1 labeling index was ~1%. In conclusion, AG exhibits characteristic features in imaging; however, its diagnosis depends on histopathological examination. The prognosis of total surgical resection is good and intraoperative ECoG may be used to assist positioning.

A systematic review of treatment outcomes in pediatric patients with intracranial ependymomas

OBJECT

Ependymoma is the third most common primary brain tumor in children. Tumors are classified according to the WHO pathological grading system. Prior studies have shown high levels of variability in patient outcomes within and across pathological grades. The authors reviewed the results from the published literature on intracranial ependymomas in children to describe clinical outcomes as they relate to treatment modality, associated mortality, and associated progression-free survival (PFS).

METHODS

A search of English language peer-reviewed articles describing patients 18 years of age or younger with intracranial ependymomas yielded data on 182 patients. These patients had undergone treatment for ependymoma with 1 of 5 modalities: 1) gross-total resection (GTR), 2) GTR as well as external beam radiation therapy (EBRT), 3) subtotal resection (STR), 4) STR as well as EBRT, or 5) radiosurgery. Mortality and outcome data were analyzed for time to tumor progression in patients treated with 1 of these 5 treatment modalities.

RESULTS

Of these 182 patients, 69% had supratentorial ependymomas and 31% presented with infratentorial lesions. Regardless of tumor location or pathological grade, STR was associated with the highest rates of mortality. In contrast, GTR was associated with the lowest rates of mortality, the best overall survival, and the longest PFS. Children with WHO Grade II ependymomas had lower mortality rates when treated more aggressively with GTR. However, patients with WHO Grade III tumors had slightly better survival outcomes after a less aggressive surgical debulking (STR+EBRT) when compared with GTR.

CONCLUSIONS

Mortality, PFS, and overall survival vary in pediatric patients with intracranial ependymomas. Pathological classification, tumor location, and method of treatment play a role in outcomes. In this study, GTR was associated with the best overall and PFS rates. Patients with WHO Grade II tumors had better overall survival after GTR+EBRT and better PFS after GTR alone. Patients with WHO Grade III tumors had better overall survival after STR+EBRT. Patients with infratentorial tumors had improved overall survival compared with those with supratentorial tumors. Progression-free survival was best in those patients with infratentorial tumors following STR+EBRT. Consideration of all of these factors is important when counseling families on treatment options.

Cell of origin determines tumor phenotype in an oncogenic Ras/p53 knockout transgenic model of high-grade glioma

Human high-grade gliomas (HGGs) are known for their histologic diversity. To address the role of cell of origin in glioma phenotype, transgenic mice were generated in which oncogenic Ras and p53 deletion were targeted to neural stem/progenitor cells (NSPCs) and mature astrocytes. The hGFAP-Cre/Kras/p53 mice develop multifocal HGGs that vary histopathologically and with respect to the expression of markers associated with NSPCs. One HGG pattern strongly expressed markers of NSPCs and arose near the subventricular zone. Additional nonoverlapping patterns that recapitulate human HGG variants were present simultaneously in the same brain. These neoplastic foci were more often cortical or leptomeningeal based, and the neoplastic cells lacked expression of NSPC markers. To determine whether cell of origin determines tumor phenotype, astrocytes and NSPCs were harvested from neonatal mutant pups. Onorthotopic transplantation, early-passage astrocytes and NSPCs formed tumors that differed in engraftment rates, latency to clinical signs, histopathology, and protein expression. Astrocyte-derivedtumors were more aggressive, had giant-cell histology, and glial fibrillary acidic protein expression. The NSPC-derived tumors retained NSPC markers and showed evidence of differentiation along astrocytic, oligodendroglial, and neuronal lineages. These results indicate that identical tumorigenic stimuli produce markedly different glioma phenotypes, depending on the differentiation status of the transformed cell.

Imaging characteristics of an unusual, high-grade angiocentric glioma: a case report and review of the literature

Angiocentric gliomas have recently been reclassified as a separate central nervous system tumor. Few cases have been reported, and most of those correspond to slow-growing, low-grade neoplasms in very young pediatric patients. Here we describe magnetic resonance imaging findings (including diffusion imaging, spectroscopy and tractography) in an unusual higher-grade neoplasm with pathologic features suggestive of an angiocentric glioma in a 15-year-old male. The tumor had mild heterogeneous enhancement on magnetic resonance imaging, and a low apparent diffusion coefficient (9.9 × 10(-4) mm(2)s(-1)), consistent with an intermediate-to-high cellularity tumor. Spectroscopic imaging showed elevated choline/phosphocreatine and choline/N-acetyl aspartate ratios, suggesting an unusually aggressive tumor. We conclude that angiocentric glioma should not be excluded from consideration at primary diagnosis, particularly in teenaged patients nearing adulthood.

Long-term epilepsy-associated tumors

The term long-term epilepsy associated tumor (LEAT) encompasses lesions identified in patients investigated for long histories (often 2 years or more) of drug-resistant epilepsy. They are generally slowly growing, low grade, cortically based tumors, more often arising in younger age groups and in many cases exhibit neuronal in addition to glial differentiation. Gangliogliomas and dysembryoplastic neuroepithelial tumors predominate in this group. LEATs are further united by cyto-architectural changes that may be present in the adjacent cortex which have some similarities to developmental focal cortical dysplasias (FCD); these are now grouped as FCD type IIIb in the updated International League Against Epilepsy (ILAE) classification. In the majority of cases, surgical treatments are beneficial from both perspectives of managing the seizures and the tumor. However, in a minority, seizures may recur, tumors may show regrowth or recurrence, and rarely undergo anaplastic progression. Predicting and identifying tumors likely to behave less favorably are key objectives of the neuropathologist. With immunohistochemistry and modern molecular pathology, it is becoming increasingly possible to refine diagnostic groups. Despite this, some LEATs remain difficult to classify, particularly tumors with "non-specific" or diffuse growth patterns. Modification of LEAT classification is inevitable with the goal of unifying terminological criteria applied between centers for accurate clinico-pathological-molecular correlative data to emerge. Finally, establishing the epileptogenic components of LEAT, either within the lesion or perilesional cortex, will elucidate the cellular mechanisms of epileptogenesis, which in turn will guide optimal surgical management of these lesions.

Brain tumors in children--current therapies and newer directions

Brain tumors are the second most common malignancy and the major cause of cancer related mortality in children. Though significant advances in neuroimaging, neurosurgery, radiation therapy and chemotherapy have evolved over the years, overall survival rate remains less than 75%. Malignant gliomas, high risk medulloblastoma with recurrence and infant brain tumors continue to be a major cause of therapeutic frustration. Even today diffuse pontine gliomas are universally fatal. Though tumors like low grade glioma have an overall excellent survival, recurrences and progression in eloquent areas pose therapeutic challenges. As research continues to unravel the biology including key molecules and signaling pathways responsible for the oncogenesis of different childhood brain tumors, novel targeted therapies are profiled. Identification of major targets like the Epidermal Growth factor Receptor (EGFR), Platelet Derived Growth Factor Receptor (PDGFR), Vascular Endothelial Growth factor (VEGF) and key signaling pathways like the MAPK and PI3K/Akt/mTOR has enabled us over the recent years to better understand tumor behavior and design tailored therapy. These efforts have improved overall survival of children with brain tumors. This review article discusses the current status of common brain tumors in children and the newer therapeutic approaches.

Chordoid glioma of the third ventricle: four cases including one case with papillary features

Chordoid glioma is a rare, slowly growing tumor of the CNS, which is always located in the third ventricle of adults. Chordoid glioma has classic histological features consisting of clusters and cords of epithelioid tumor cells embedded within a mucinous stroma with rich lymphoplasmacytic infiltrate. The important distinctive immunohistochemical feature of this neoplasm is strong and diffuse reactivity for GFAP. Here, we report four cases of chordoid glioma that occupied the anterior portion of the third ventricle or suprasellar region. These four cases were all adult females with almost typical clinical, radiological, histologic and immunohistochemical characteristics of chordoid glioma. However, in one case there was an unusual histologic finding with regard to the papillary region. In this region, elongated tumor cells were observed radiating toward a central vessel to form characteristic papillary structures. Immunohistochemically, three cases showed strong reactivity for GFAP, and one exhibited weak reactivity. All cases were focally positive for epithelial membrane antigen, CD34 and D2-40, but negative for neurofilament protein (NFP). Several ultrastructural investigations have supported the ependymal origin of chordoid glioma. In some cases of immunoreactivity for NFP, some authors have supposed that chordoid glioma originates from a multipotential stem cell with glial and neuronal cell differentiation. With regard to the present four cases with immunoreactivity for D2-40 (an ependymal marker) and CD34 (undifferentiated neural precursors) and based on previously published data, we considered that the majority of chordoid gliomas had an ependymal origin, and that a small minority might have originated from a multipotential stem cell having ependymal and neuronal cell differentiation.

Chromosomal anomalies and prognostic markers for intracranial and spinal ependymomas

Ependymomas are neoplasms that can occur anywhere along the craniospinal axis. They are the third most common brain tumor in children, representing 10% of pediatric intracranial tumors, 4% of adult brain tumors, and 15% of all spinal cord tumors. As the heterogeneity of ependymomas has severely limited the prognostic value of the World Health Organization grading system, numerous studies have focused on genetic alterations as a potential basis for classification and prognosis. However, this endeavor has proven difficult due to variations of findings depending on tumor location, tumor grade, and patient age. While many have evaluated chromosomal abnormalities for ependymomas as a whole group, others have concentrated their efforts on specific subsets of populations. Here, we review modern findings of chromosomal analyses, their relationships with various genes, and their prognostic implications for intracranial and spinal cord ependymomas.

Dual gliomas with syringomyelia in a child: case report and literature review

BACKGROUND AND IMPORTANCE

The occurrence of multiple tumors of different histopathologies in the central nervous -system is rare. Here, we report a case of a child with dual neuroepithelial tumors of different histological cell types and -review the available literature for analyzing the causal hypo-thesis.

CASE REPORT

A 7-year-old girl presented with history of headaches associated with multiple episodes of early morning projectile vomiting and visual blurring. Magnetic resonance imaging (MRI) showed a well-defined lesion in the hypothalamic region. The patient underwent resection of the tumor by the transcallosal transfornicial approach. Histopathology was suggestive of pilocytic astrocytoma. After 3 years, the patient presented with low back pain radiating to the right lower limb followed by sudden onset of weakness in both lower limbs. Recent MRI brain and spine scans showed a small residual lesion at the hypothalamus with D1 to D10 syrinx. A T1 hypointense and T2 hyperintense cystic lesion from D10 to S2 with intensely enhancing solid component at the S1, S2 region was also detected. The patient underwent L4 to S2 laminectomy and the histopathological examination revealed myxopapillary ependymoma.

CONCLUSION

The presence of multiple neuroepithelial tumors of different histopathology in the same patient is extremely rare, and we report one such case of dual gliomas with hypothalamic pilocytic astrocytoma and cauda equina myxopapillary ependymoma in a 10-year-old patient. During the course of development, displacement and dedifferentiation of primitive totipotent neuroepithelial germ cells may be a causal factor for the appearance of the different neuroepithelial tumors in neuraxis concomitantly or subsequently, which might be substantiated by common cytogenetic abnormalities in different neuroepithelial tumor histogenesis.

Papillary tumour of the pineal region

Papillary tumour of the pineal region (PTRR) is one of the new tumour entities to be included in the latest World Health Organization classification of central nervous system tumours. We report two illustrative patients, a 25-year-old female who presented following a head injury sustained from a fall due to gait disturbances, and a 42-year-old man who presented with headaches. Histology of both cases showed distinct papillary growth patterns with lining of the papillae by multi-layered cuboidal to columnar cells, prominent perivascular rosette and focal true rosette formation. Immunohistochemistry exhibited strong cytokeratin immunoreactivity in addition to CD56, focal S100, glial fibrillary acidic protein and neuron specific enolase positivity which supported a diagnosis of PTPR in both patients. Postoperatively, both patients underwent courses of adjuvant radiation therapy. One patient reported local recurrence of the tumour 23 months after surgery. While PTPR may have been misdiagnosed in the past, clear and consistent characteristics are beginning to be elucidated in the published reports and literature, which have been reviewed. As a relatively new distinct clinicopathological entity, prognostic data are limited and guidelines for treatment protocols are still being investigated in view of its propensity for local recurrence.

Ependymoma and choroid plexus papilloma as synchronous multiple neuroepithelial tumors in the same patient: a case report and review of literature

BACKGROUND AND IMPORTANCE

We report the case of a patient with multiple neuroepithelial tumors of different histological cell types. In this patient, synchronous appearance of tumors of the central nervous system, ie, cervical ependymoma and a fourth ventricle choroid plexus papilloma, was noted.

CLINICAL PRESENTATION

A 36-year-old man presented with sensory disturbance of the bilateral upper extremities. Magnetic resonance imaging revealed a heterogeneously enhanced mass with syringomyelia in the upper cervical cord and a well-enhanced mass in the fourth ventricle. The patient underwent bilateral suboccipital craniotomy and laminectomy from the level of C1 to C3 for both lesions. The lesions were grossly resected. Histological and immunohistochemical examinations revealed that the cervical tumor was an ependymoma, and the fourth ventricle tumor was a choroid plexus papilloma.

CONCLUSION

The appearance of synchronous multiple neuroepithelial tumors of different histological cell types is extremely rare, and this is the first known case of ependymoma occurring synchronously with choroid plexus papilloma, both tumors having different histological cell types. Displacement and maldifferentiation of primitive, multipotent neuroepithelial cells may be a causative factor for this unique presentation.

Cortical ependymoma: an unusual epileptogenic lesion

OBJECT

Supratentorial cortical ependymomas (CE) are rare, with 7 cases reported. The lesions, typically occurring in the superficial cortex in young adults and associated with a history of seizures, are not fully characterized. Furthermore, their relationship with the recently described angiocentric glioma (AG) is still being debated. This study was undertaken to summarize the authors' experience with CEs.

METHODS

Between 1997 and 2009, 202 cases of ependymoma were surgically treated at the Mayo Clinic, 49 of which were supratentorial. Among these, 9 CE cases were retrospectively identified. Clinical, imaging, and pathological features of each case were reviewed.

RESULTS

Tumors arose from the frontal (5 cases), parietal (3), and occipital (1) lobes. No tumor occurred in the temporal lobe, despite its reported association with seizures. The mean age at presentation was 27 ± 19 years (± SD) and age at resection was 36 ± 16 years. The mean size of the lesion was 16 ± 14 cm(3). Seizures were the presenting symptom in 78%. Cross-sectional imaging in 8 cases was characterized by a heterogeneous mass with multiple cystlike areas and enhancement of the soft-tissue component. Gross-total resection was achieved in 8 of 9 tumors. Pathologically, 6 were low-grade (WHO Grade II) and 3 were anaplastic (WHO Grade III) ependymomas. All tumors exhibited the focal presence of perivascular pseudorosettes, but only 1 (11%) exhibited the focal presence of a true rosette. A bipolar spindle cell component resembling AG was present in 3 (33%) and "Schwannian-like" nodules in 2 (22%). Subpial aggregation and peripheral infiltration were present in 4 cases (44%). With a mean postsurgery follow-up of 62 ± 38 months, only 2 lesions recurred locally after imaging-confirmed gross-total resection, both being Grade III. In 5 (71%) of 7 patients presenting with seizures an Engel Class I outcome was achieved.

CONCLUSIONS

Cortical ependymomas represent a rare type of ependymoma occurring superficially in the cortex. Morphologically, these tumors are protean, varying from classic to epithelioid, clear cell, and tanycytic. Some also exhibited features typical of AG. Most tumors were low grade and cured with resection. Anaplastic tumors occur and may recur locally despite provision of radiation therapy. Cortical ependymomas frequently, but not always, present with seizures, but despite their high association with epilepsy, none occurred in the temporal lobe in any of the authors' 9 patients. Overall, CEs appear to have a relatively favorable prognosis compared with other supratentorial ependymomas.

Angiocentric glioma: a case report and review of the literature

Angiocentric glioma (AG) is a rare central nervous system (CNS) neoplasm that was only recently recognized by the World Health Organization (WHO). AG occurs in a broad age range, shows no gender predilection, and arises superficially in the cerebrum, usually resulting in medically intractable seizures. Most cases are cured by surgical excision alone, consistent with a WHO grade I neoplasm. We report a case of an AG in the right frontal lobe of a 57-year-old female, emphasizing the cytologic and immunohistochemical features, including confirmation and comparison with the surgical specimen. To our knowledge, this is the first report detailing the cytology of AG, including demonstration of important diagnostic findings that were only appreciated in the cytologic preparations and not in the smears or the surgical specimen. We also compare and contrast AG to other entities in the differential diagnosis and include a review of the literature.

Neuronal differentiation distinguishes supratentorial and infratentorial childhood ependymomas

Ependymomas are glial neoplasms occurring in any location throughout the central nervous system and supposedly are derived from radial glia cells. Recent data suggest that these tumors may have different biological and clinical behaviors according to their location. Pediatric supratentorial and infratentorial ependymoma (SE and IE) were compared with respect to clinical and radiological parameters and immunohistochemistry (IHC). Neuronal markers were specifically assessed by IHC and quantitative PCR (qPCR). No single morphological or radiological characteristic was associated with location or any neuronal marker. However, there was a significant overexpression of neuronal markers in SE compared with IE: neurofilament light polypeptide 70 (NEFL)-positive tumor cells were found in 23 of 34 SE and in only 4 of 32 IE (P < .001). Among SE, 10 of 34 exhibited high expression of NEFL, defined as more than 5% positive cells. qPCR confirmed the upregulation of neuronal markers (NEFL, LHX2, FOXG1, TLX1, and NPTXR) in SE compared with IE. In addition, strong NEFL expression in SE was correlated with better progression-free survival (P = .007). Our results support the distinction of SE and IE. SEs are characterized by neuronal differentiation, which seems to be associated with better prognosis.

Glioma diagnosis: immunohistochemistry and beyond

Clinicians and pathologists have been inundated by published reports of new and potentially interesting diagnostic, prognostic, and putative predictive "markers" whose expression (or loss) holds great promise for more enlightened diagnoses and ultimately better patient care. Although an understanding of therapeutically (and possibly diagnostically) relevant pathways of glioblastoma may be at hand, significant challenges remain. Many immunohistochemical and genetic tests have proven to be useful in the stratification of clinical trials, whereas the utility of many others for the day-to-day practice of pathology awaits further study and validation. The importance of critical literature review and careful consideration of practical issues such as test standardization, compliance, cost-effectiveness, and availability must all be considered before implementing any new diagnostic test. This review will focus on the role of immunohistochemistry in the routine diagnosis of astrocytic and oligodendrocytic tumors and in assisting with the diagnosis of some less common gliomas that have ependymal-like features. It will conclude with a summary of molecular and genetic studies, which not only hold great promise for improved diagnosis, but also reveal prognostic information on disease outcome and predict response to treatment or provide biologic targets for novel therapies.

Intramedullary papillary ependymoma with choroid plexus differentiation and cerebrospinal fluid dissemination to the brain

This 8-year-old girl presented with a papillary ependymoma in the thoracic spinal cord. Resection was followed by recurrence at the primary site and later in the lumbosacral thecal sac, followed by cerebrospinal fluid dissemination to the brain approximately 5 years after her initial presentation. The tumor showed cytological and immunohistochemical features overlapping those of classic ependymomas and choroid plexus tumors similar to those seen in uncommon supratentorial papillary ependymomas, also known as papillary tumors of the pineal region. The histopathological and clinical courses of this rare spinal papillary ependymoma exhibiting mixed ependymal and choroid plexus-like differentiation are discussed.

Ependymal cells: biology and pathology

The literature was reviewed to summarize the current understanding of the role of ciliated ependymal cells in the mammalian brain. Previous reviews were summarized. Publications from the past 10 years highlight interactions between ependymal cells and the subventricular zone and the possible role of restricted ependymal populations in neurogenesis. Ependymal cells provide trophic support and possibly metabolic support for progenitor cells. Channel proteins such as aquaporins may be important for determining water fluxes at the ventricle wall. The junctional and anchoring proteins are now fairly well understood, as are proteins related to cilia function. Defects in ependymal adhesion and cilia function can cause hydrocephalus through several different mechanisms, one possibility being loss of patency of the cerebral aqueduct. Ependymal cells are susceptible to infection by a wide range of common viruses; while they may act as a line of first defense, they eventually succumb to repeated attacks in long-lived organisms. Ciliated ependymal cells are almost certainly important during brain development. However, the widespread absence of ependymal cells from the adult human lateral ventricles suggests that they may have only regionally restricted value in the mature brain of large size.

Ultrastructural evidence of ependymal differentiation in a genetically proven atypical teratoid/rhabdoid tumor

INTRODUCTION

We describe a case of genetically proven atypical teratoid/rhabdoid tumor (ATRT), showing ultrastructural evidence of ependymal differentiation. Such differentiation has not been reported so far in ATRT.

CONCLUSION

This finding supports the concept that ATRTs as the majority of central nervous system embryonal tumors may derive from an immature and pluripotent neuroectodermal cell capable of differentiating along multiple lineages.

Classification and controversies in pathology of ependymomas

PURPOSE

Bailey and Cushing established ependymoma as a brain tumour entity in the first brain tumour classification (1926). Diagnosis of ependymomas is not subject to controversy as long as other tumours presenting ependymoma-like features have been ruled out. Grading conversely is a source of debate. Description of histological features establishing diagnosis and grading of ependymomas may help to better understand this controversy.

METHODS

Literature has been reviewed using PubMed with the following key words: ependymoma, +/- prognosis, +/- biomaker, +/- grading, +/- immunohistochemistry, +/- proliferative index.

RESULTS

Grading controversy arises from elusive WHO features and individual characteristics of ependymomas including tumour location, tumour pattern/variant and variable expression of biomarkers.

CONCLUSION

There is a need for a grading scheme with a proven general ability to dissociate grades, and to predict individual clinical evolution. Only then will stratified and targeted therapeutics for ependymal tumours be possible.