Pediatric neuroblastic brain tumors containing abundant neuropil and true rosettes

Embryonal and pineal tumours

Embryonal and pineal tumours represent a diverse group of central nervous system (CNS) neoplasms. While many of the small round blue cell tumours that make up the embryonal neoplasms share similar histologic qualities, there are several morphologic and cytologic characteristics that are useful in distinguishing different tumour types. Similarly, pineal parenchymal tumours represent clinically diverse tumours, ranging from benign to overtly malignant. The most recent iteration of the World Health Organization Classification of CNS Tumours expanded greatly on the significance of molecular alterations in brain tumour diagnostics. In this article, we summarize the salient cytologic and histologic features of CNS embryonal and pineal tumours, and highlight diagnostically relevant molecular alterations within each tumour type.

Embryonal Tumors of the Central Nervous System with Multilayered Rosettes and Atypical Teratoid/Rhabdoid Tumors

The 2016 WHO classification of tumors of the central nervous system affected importantly the group of CNS embryonal tumors. Molecular analysis on methylome, genome, and transcriptome levels allowed better classification, identification of specific molecular hallmarks of the different subtypes of CNS embryonal tumors, and their more precise diagnosis. Routine application of appropriate molecular testing and standardized reporting are of pivotal importance for adequate prognosis and treatment, but also for epidemiology studies and search for efficient targeted therapies. As a result of this approach, the term primitive neuroectodermal tumor-PNET was removed and a new clinic-pathological entity was introduced-Embryonal tumor with multilayered rosettes (ETMR). The group of CNS embryonal tumors include also medulloblastoma, medulloepithelioma, CNS neuroblastoma, CNS ganglioneuroblastoma, atypical teratoid/rhabdoid tumor (ATRT) and their subtypes. This chapter will focus mainly on ETMR and ATRT. Embryonal tumors with multilayered rosettes and the atypical teratoid/rhabdoid tumors are undifferentiated or poorly differentiated tumors of the nervous system that originate from primitive brain cells, develop exclusively in childhood or adolescence, and are characterized by a high degree of malignancy, aggressive evolution and a tendency to metastasize to the cerebrospinal fluid. Their clinical presentation is similar to other malignant, intracranial, neoplastic lesions and depends mainly on the localization of the tumor, the rise of the intracranial pressure, and eventually the obstruction of the cerebrospinal fluid pathways. The MRI image characteristics of these tumors are largely overlappingintra-axial, hypercellular, heterogeneous tumors, frequently with intratumoral necrosis and/or hemorrhages. Treatment options for ETMR and ATRT are very restricted. Surgery can seldom achieve radical excision. The rarity of the disease hampers the establishment of a chemotherapy protocol and the usual age of the patients limits severely the application of radiotherapy as a therapeutic option. Consequently, the prognosis of these undifferentiated, malignant, aggressive tumors remains dismal with a 5-year survival between 0 and 30%.

Rare embryonal and sarcomatous central nervous system tumours: State-of-the art and future directions

The introduction of molecular methods into the diagnostics of central nervous system (CNS) tumours and the subsequent deciphering of their molecular heterogeneity has resulted in a significant impact on paediatric neurooncology. Particularly in the field of rare embryonal and sarcomatous CNS tumours, novel tumour types have been delineated and introduced in the recent 5th edition of the WHO classification of CNS tumours. The rarity and novelty of these tumour types result in diagnostic and therapeutic challenges. Apart from distinct histopathological and molecular features, these tumour types exhibit characteristic clinical properties and require different therapeutic approaches for optimal patient management. However, based on the limited availability of clinical data, current therapeutic recommendations have to be based on data from small, predominantly retrospective patient cohorts. Within this article, we provide guidance for diagnostic work-up and clinical management of rare CNS embryonal tumours ('embryonal tumour with multi-layered rosettes', ETMR; 'CNS neuroblastoma, FOXR2-activated', CNS NB-FOXR2; 'CNS tumour with BCOR-ITD, CNS BCOR-ITD) and rare CNS sarcomatous tumours ('primary intracranial sarcoma, DICER1-mutant', CNS DICER1; 'CIC-rearranged sarcoma', CNS CIC). By emphasizing the significant consequences on patient management in paediatric CNS tumours, we want to encourage wide implementation of comprehensive molecular diagnostics and stress the importance for joint international efforts to further collect and study these rare tumour types.

Embryonal tumors with multilayered rosettes, C19MC-altered or not elsewhere classified: Clinicopathological characteristics, prognostic factors, and outcomes of 17 children from 2018 to 2022

Objective

Embryonal tumors with multilayered rosettes (ETMRs) are a histologically heterogeneous entity and gather embryonal tumors with abundant neuropil and true rosettes (ETANTRs), ependymoblastoma, and medulloepithelioma. ETMRs are highly aggressive and associated with poorer clinical courses. However, cases of this entity are rare, and advances in molecular genetics and therapy are minor. The purpose of our study was to retrospectively analyze the clinical, pathological features, and prognostic factors of ETMRs.

Methods

Our cohort consisted of 17 patients diagnosed with ETMRs in our hospital from 2018 to 2022, and two of them were lost to follow-up. Clinical data were retrieved, and immunohistochemistry and genetic analyses were performed.

Results

Among 17 cases, 16 were ETANTRs, and one was medulloepithelioma. Morphologically, tumor cells of ETANTRs could transform into anaplasia and lose the biphasic architecture during tumor progression. Immunohistochemistry of LIN28A revealed positive expression in 17 cases, and the expression of LIN28A was more intense and diffuse in the recurrent lesions than in primaries. The increased N-MYC copy numbers were detected in the primary tumor and recurrence of patient 8. Moreover, the incidence of metastatic disease was 100% in patients aged > 4 years and 18% in the younger group. For patients receiving chemotherapy, the median overall survival time was 7.4 months, while that of those who didn’t receive it was 1.2 months. Nevertheless, surgical approaches, radiotherapy, age at presentation, gender, tumor location, and metastatic status were not associated with independent prognosis.

Conclusion

ETANTR might not present as the typical morphologies during tumor progression, so analyses of C19MC amplification and Lin28A antibody are indispensable for diagnosing ETMRs accurately. Children aged > 4 years tend to have a higher rate of metastasis in ETMRs. Chemotherapy is the only prognostic factor for ETMRs patients with a favorable prognosis. The biological nature and clinical patterns for recurrent diseases need to be further demonstrated to predict prognosis and guide treatment.

Case report: Infratentorial Embryonal Tumor with Abundant Neuropil and True Rosettes (ETANTR) in an 8-month-old Maine Coon

An 8-month-old female Main Coon with a history of recurrent behavioral changes and anorexia was presented with sternal recumbency and depression. Within 5 days, the cat progressively worsened with symptoms of stupor and coma and was euthanized. At post-mortem examination, a solid, grayish infratentorial mass located in the midline rostrally to the cerebellum, was observed. Histologically, highly cellular clusters of small-to-medium undifferentiated cells were intermingled with paucicellular areas with fibrillary eosinophilic (neuropil-like) appearance. Numerous multilayered (ependymoblastic) true rosettes were present. The mitotic activity was frequent (up to 15 mitoses/HPF), involving both undifferentiated cells and rosettes. By immunohistochemistry (IHC), tumor cells were diffusely positive for vimentin, variably for synaptophysin, S-100, and NSE, and focally for NeuN; they were negative for GFAP and CK AE1/AE3. The histological and IHC aspects were consistent with an Embryonal Tumor with Abundant Neuropil and True Rosettes (ETANTR). Embryonal neoplasms of the central nervous system (CNS) are characterized by primitive undifferentiated cells, able to develop toward neuronal, glial, ependymal, and mesenchymal lines. Although extremely rare, juvenile embryonal tumors should be considered in the differentials of CNS disorders in young cats.

Bromodomain and Extra-Terminal Protein Inhibitors: Biologic Insights and Therapeutic Potential in Pediatric Brain Tumors

Pediatric brain tumors have surpassed leukemia as the leading cause of cancer-related death in children. Several landmark studies from the last two decades have shown that many pediatric brain tumors are driven by epigenetic dysregulation within specific developmental contexts. One of the major determinants of epigenetic control is the histone code, which is orchestrated by a number of enzymes categorized as writers, erasers, and readers. Bromodomain and extra-terminal (BET) proteins are reader proteins that bind to acetylated lysines in histone tails and play a crucial role in regulating gene transcription. BET inhibitors have shown efficacy in a wide range of cancers, and a number have progressed to clinical phase testing. Here, we review the evidence for BET inhibitors in pediatric brain tumor experimental models, as well as their translational potential.

A surgical case of pediatric spinal medulloepithelioma

Embryonal tumor with multilayered rosettes (ETMR), C19MC-altered was introduced to the World Health Organization classification of central nervous system tumors in 2016. It is characterized by amplification or fusion of the chromosome 19 microRNA cluster (C19MC) locus at 19q13.42. Medulloepithelioma also an ETMR but lacks C19MC alteration. We report a rare case of spinal medulloepithelioma in a 2-year-old boy and review the literature.

Evaluation and Diagnosis of Central Nervous System Embryonal Tumors (Non-Medulloblastoma)

Since the 1990s, the sheer number of defined central nervous system (CNS) embryonal tumor entities has continuously increased, with the trend accelerating in the most recent editions of the World Health Organization (WHO) Classification of Tumours of the CNS. The introduction of increasingly specific tumor groups is an effort to create more internally homogeneous categories, to allow more precise prognostication, and potentially to develop targeted therapies. However, these ever-smaller categories within an already rare group of tumors pose a challenge for pediatric pathologists. In this article we review the current categorization of non-medulloblastoma CNS embryonal tumors (including atypical teratoid/rhabdoid tumor, cribriform neuroepithelial tumor, embryonal tumor with multilayered rosettes, CNS neuroblastoma, FOXR2-activated, and CNS tumor with BCOR internal tandem duplication) and provide an overview of available ancillary techniques to characterize these tumors. We provide a practical approach to workup and development of an integrated diagnosis for CNS embryonal tumors.

Embryonal Tumor With Multilayered Rosettes of the Parietooccipital Region: A Case Report

Embryonal tumor with multilayered rosettes is a rare and highly malignant early childhood brain tumor. We report a case of embryonal tumor with multilayered rosettes in the parietooccipital region of a 2-year-old girl. Histopathology of the tumor demonstrated amplification of the 19q13.42 locus and strong positivity for LIN28A. Treatment was multimodal and included 3 surgical resections, adjuvant chemotherapy with autologous stem cell rescue, and focal radiotherapy. The use of the agents vorinostat and isotretinoin, and the addition of focal radiation have not been extensively described in this patient population, but may attribute to our patient's sustained remission at 2.5-years follow-up.

[Embryonal tumor with multilayered rosettes (ETMR): case report and literature review]

Embryonal tumor with multilayered rosettes (ETMR) is a rare and highly malignant brain tumor that develops in children younger 4 years old. This neoplasm is characterized by extremely aggressive course, low sensitivity to chemotherapy and radiotherapy. Thanks to the progress of pathologists, diagnosis of ETMR is now available using immunohistochemical examination with LIN28A and SALL4 antibodies. Moreover, detection of microRNA amplification in the 19q13.42 locus by fluorescent hybridization in situ allows an unmistakable diagnosis. The authors describe clinical course and treatment outcome in a 2-year-old patient with a giant tumor of the right parietotemporal region. Postoperative histological examination verified ETMR. Despite adjuvant treatment, we observed fast progression of disease and unfavorable outcome after 5 months. Case report is supplemented by literature review.

CONCLUSION

ETMR is very rare and poorly understood neoplasm. The authors present a giant hemispheric ETMR in a 2-year-old boy with an extremely aggressive course of disease. Despite the advances in diagnosis and treatment of CNS tumors in children, there are currently more questions than answers regarding ETMR. Pooled analysis of all available data with large-scale studies is needed. It is necessary to emphasize an exceptional role of each clinical case for global study of this tumor. Timely adjuvant/neoadjuvant therapy in highly specialized centers is also essential.

Embryonal tumor with multilayered rosettes; rare pediatric CNS tumor. A case report and review of literature

Embryonal tumor with multilayered rosettes (ETMR), C19MC-altered is a newly designated entity of the embryonal tumors of the central nervous system (CNS) according to the 2016 WHO classification system of CNS. Characteristically, these tumors are newly defined based on their specific molecular genetic amplification in chromosome 19q13.42 found at locus C19MC. To the best of our knowledge, we present the first reported case of ETMR in Saudi Arabian pediatric population. A 2-year-old boy presented to the hospital with generalized tonic-colonic seizure, vomiting, irritability, and inability to walk. Computed tomography (CT) scan showed a large left thalamic supratentorial brain tumor. The tumor measured 6.1 × 5.6 × 5.6 cm and was characterized by cystic changes, prominent vasculature, and calcifications. Histopathology, immunohistochemistry examination, and fluorescence in situ hybridization (FISH) analysis confirmed the diagnosis of ETMR. In addition to reporting this rare case, we provide a brief literature review, treatment options, patient outcome, and disease prognosis.

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Embryonal tumor with multilayered rosettes (ETMR), C19MC-altered is a new entity of the embryonal brain tumors.

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Genomic alterations include a gain of chromosome 2, gain of chromosome 11, and gain/low-level amplification of 19q13.42 (ultimately resulting in TTYH1-C19MC fusion).

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The clinical behavior is usually aggressive, with dismal with poor outcome.

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Histopathologic evaluation, immunohistochemistry, and fluorescence in situ hybridization (FISH) analysis are required to confirm the diagnosis of ETMR.

Clinical phenotypes and prognostic features of embryonal tumours with multi-layered rosettes: a Rare Brain Tumor Registry study

BACKGROUND

Embryonal tumours with multi-layered rosettes (ETMRs) are a newly recognised, rare paediatric brain tumour with alterations of the C19MC microRNA locus. Due to varied diagnostic practices and scarce clinical data, disease features and determinants of outcomes for these tumours are poorly defined. We did an integrated clinicopathological and molecular analysis of primary ETMRs to define clinical phenotypes, and to identify prognostic factors of survival and key treatment modalities for this orphan disease.

METHODS

Paediatric patients with primary ETMRs and tissue available for analyses were identified from the Rare Brain Tumor Consortium global registry. The institutional histopathological diagnoses were centrally re-reviewed as per the current WHO CNS tumour guidelines, using histopathological and molecular assays. Only patients with complete clinical, treatment, and survival data on Nov 30, 2019, were included in clinicopathological analyses. Among patients who received primary multi-modal curative regimens, event-free survival and overall survival were determined using Cox proportional hazard and log-rank analyses. Univariate and multivariable Cox proportional hazard regression was used to estimate hazard ratios (HRs) with 95% CIs for clinical, molecular, or treatment-related prognostic factors.

FINDINGS

159 patients had a confirmed molecular diagnosis of primary ETMRs (median age at diagnosis 26 months, IQR 18-36) and were included in our clinicopathological analysis. ETMRs were predominantly non-metastatic (94 [73%] of 128 patients), arising from multiple sites; 84 (55%) of 154 were cerebral tumours and 70 (45%) of 154 arose at sites characteristic of other brain tumours. Hallmark C19MC alterations were seen in 144 (91%) of 159 patients; 15 (9%) were ETMR not otherwise specified. In patients treated with curative intent, event-free survival was 57% (95% CI 47-68) at 6 months and 31% (21-42) at 2 years; overall survival was 29% (20-38) at 2 years and 27% (18-37) at 4 years. Overall survival was associated with non-metastatic disease (HR 0·48, 95% CI 0·28-0·80; p=0·0057) and non-brainstem location (0·42 [0·22-0·81]; p=0·013) on univariate analysis, as well as with gross total resection (0·30, 0·16-0·58; p=0·0014), high-dose chemotherapy (0·35, 0·19-0·67; p=0·0020), and radiotherapy (0·21, 0·10-0·41; p<0·0001) on multivariable analysis. 2-year event-free and overall survival was 0% at 2 years in patients treated with conventional chemotherapy without radiotherapy (regardless of surgery extent), and 21% (95% CI 1-41) and 30% (6-54), respectively, in patients treated with high-dose chemotherapy, and gross total resection without radiotherapy. 2-year event-free survival in patients treated with high-dose chemotherapy and radiotherapy was 66% (95% CI 39-93) for patients with gross total resection and 44% (7-81) for patients with sub-total resection. 2-5-year overall survival was 66% (95% CI 33-99, p=0·038) for patients with gross total resection and 67% (36-98, p=0·0020) for patients with sub-total resection.

INTERPRETATION

Prompt molecular diagnosis and post-surgical treatment with intensive multi-modal therapy tailored to patient-specific risk features could improve ETMR survival.

FUNDING

Canadian Institute of Health Research, Canada Research Chair Awards, Australian Lions Childhood Cancer Research Foundation, Spanish Society of Pediatrics, Consejería de Salud y Familias de la Junta de Andalucía, Miracle Marnie, Phoebe Rose Rocks, Tali's Funds, Garron Cancer Centre, Grace's Walk, Meagan's Hug, Brainchild, Nelina's Hope, and Jean Martel Foundation.

Intradural Pediatric Spinal Tumors: An Overview from Imaging to Novel Molecular Findings

Pediatric spinal tumors are rare and account for 10% of all central nervous system tumors in children. Onset usually occurs with chronic nonspecific symptoms and may depend on the intra- or extradural neoplastic location. Meningiomas, schwannomas, and neurofibromas are the most common intradural-extramedullary lesions, while astrocytomas and ependymomas represent the majority of intramedullary tumors. The new molecular discoveries regarding pediatric spinal cancer currently contribute to the diagnostic and therapeutic processes. Moreover, some familial genetic syndromes can be associated with the development of spinal tumors. Currently, magnetic resonance imaging (MRI) is the standard reference for the evaluation of pediatric spinal tumors. Our aim in this review was to describe the imaging of the most frequent intradural intra/extramedullary pediatric spinal tumors and to investigate the latest molecular findings and genetic syndromes.

Treatment of Embryonal Tumours with Multilayered Rosettes with Carboplatin/Etoposide Induction and High-dose Chemotherapy within the Prospective P-HIT Trial

BACKGROUND

Embryonal tumours with multilayered rosettes (ETMR) are highly aggressive tumours occurring in early childhood. Published clinical data refer to retrospective, heterogeneously treated cohorts. Here, we describe the outcome of patients treated according to the prospective P-HIT trial and subsequent HIT2000-interim-registry.

PATIENTS AND METHODS

Age-stratified treatment included carboplatin/etoposide-induction, tandem-high-dose chemotherapy ("CARBO/ETO+HDCT") and response-stratified radiotherapy. Patients with centrally reviewed neuropathological and molecularly confirmed diagnosis of ETMR recruited within the P-HIT trial (2001-2011; n=19), the HIT2000-interim-registry (2012-2014; n=12) and earlier HIT-trials (n=4) were selected for analysis.

RESULTS

Age-adjusted incidence rate was 1.35 per 1 million children (aged 1-4 years) in the years 2012-2014. Median age at diagnosis for 35 patients was 2.9 years. Metastases at diagnosis were detected in 9 patients. One patient died due to postoperative complications. For 30 patients with non-brainstem tumour location, 5-year progression-free (PFS) and overall survival (OS) were 35% and 47% after treatment with CARBO/ETO+HDCT (n=17), compared to 0% and 8% with other treatments (n=13, p[OS]=0.011). All 4 patients with brainstem tumour died within 10 months after diagnosis. By multivariable analysis, supratentorial location: (HR[PFS]:0.07 [95%CI:0.01-0.38], p=0.003), localised disease (M0): (HR[OS] M0, no residual tumor:0.30 [95%CI:0.009-1.09], p=0.068; M0, residual tumor:0.18 [95%CI: 0.04-0.76], p=0.020) and CARBO/ETO+HDCT treatment (HR[OS]:0.16 [95%CI:0.05-054], p=0.003) were identified as independent prognostic factors. Of 9 survivors, 6 were treated with radiotherapy (craniospinal 4; local 2).

CONCLUSIONS

Our data indicate improved survival with intensified chemotherapy (CARBO/ETO+HDCT). However, despite intensive treatment, the outcome was poor. Thus, innovative therapies need to be evaluated urgently in an upfront setting.

Clinicopathological characteristics and outcomes in embryonal tumor with multilayered rosettes: A decade long experience from a tertiary care centre in North India

BACKGROUND

Embryonal tumor with multilayered rosettes (ETMR) are a heterogenous group clinically, pathologically and topographically. Due to limited cases, data regarding its molecular genetics, pathology and prognostic factors is evolving. We retrospectively analysed our cohort of ETMR over last decade in order to study their clinicopathological characteristics and outcome.

METHODS

Our cohort consisted of patients diagnosed with Embryonal tumor with abundant neuropil and true rosettes (ETANTR)/Ependymoblastoma (EBL)/ Medulloepithelioma (MEPL) over the past decade. Clinical details, including outcome and imaging data was retrieved. Histological analysis including immunohistochemical work-up was performed.

RESULTS

Cohort included 15 patients with age range between 1 and 28 years and M:F ratio of 1.5:1. Supratentorial location predominated in comparison to tumors arising in posterior fossa. ETANTR and EBL patterns were equally distributed (40% each), followed by one case each of mixed pattern (EBL + ETANTR), MEPL and embryonal tumor, unclassified. All tumors readily expressed LIN 28A and INI-1 was retained. Recurrence with evidence of glial and rhabdoid differentiation was noted in a single patient 9 months following resection. Follow-up period ranged from 1 to 31 months, with overall median survival of 6.4 months. Eight patients were planned for adjuvant treatment following surgery, of which only four could complete it. All patients, except for one, succumbed to the disease.

CONCLUSIONS

ETMR have a heterogenous morphology and gathers ETANTR, EBL, MEPL within its spectrum. Following treatment, the recurrent tumor may feature glial/rhabdoid differentiation. LIN28A is expressed in all cases, however should be interpreted in context of histology. Prognosis of ETMR remains dismal despite multimodal therapy.

Embryonal tumors with multilayered rosettes: A tertiary care centre experience

BACKGROUND

Embryonal tumors with multilayered rosettes (ETMR) is an extremely rare and highly aggressive tumor. It includes three distinct entities i.e, embryonal tumor with abundant neuropil and true rosettes (ETANTR), ependymoblastoma (EBL) and medulloepithelioma (MEPL). Here, we present our institutional experience of seven ETMR cases treated over a period of five years.

MATERIALS AND METHODS

Patients' records from 2015 to 2019 were reviewed manually and electronically to retrieve the data. Clinicopathological and outcome details of ETMR cases were entered in a predesigned proforma.

RESULTS

A total of seven cases of ETMR were registered from 2015 to 2019 with a median age at presentation of four years (range 3-7 years). All patients underwent surgery. However, only three patients completed the planned adjuvant treatment, comprising of focal radiotherapy (RT) alone, craniospinal irradiation (CSI) alone and CSI followed by six cycles of chemotherapy in one patient each respectively. Two patients commenced CSI but deteriorated during RT and thereafter needed best supportive care. Two patients could not be started on any adjuvant treatment. Unfortunately, six patients succumbed to their disease within one year of their diagnosis. Only one patient who received both CSI and adjuvant chemotherapy is alive at 15 months of diagnosis.

CONCLUSION

ETMR is a rare and aggressive entity. Majority of the patients die within one year of the diagnosis despite multimodality treatment.

Embryonal tumors with multi-layered rosettes: a disease of dysregulated miRNAs

INTRODUCTION

ETMRs are highly lethal, pediatric embryonal brain tumors, previously classified as various histologic diagnoses including supratentorial primitive neuroectodermal tumors (sPNET) and CNS PNET. With recognition that these tumors harbor recurrent amplification of a novel oncogenic miRNA cluster on chr19, C19MC, ETMRs were designated as a distinct biological and molecular entity with a spectrum of histologic and clinical manifestations.

METHODS

We reviewed published literature describing clinical presentation, the genetic and epigenetic drivers of oncogenesis, and recent therapeutic strategies adopted to combat these aggressive tumors.

RESULTS

As a consequence of C19MC amplification, ETMRs upregulate several oncogenic and pluripotency proteins, including LIN28A, DNMT3B and MYCN, that confer a unique epigenetic signature reminiscent of nascent embryonic stem cells. In this review, we focus on the dysregulation of miRNAs in ETMR, the major pathogenic mechanism identified in this disease.

CONCLUSION

Despite the use of multi-modal therapeutic regimens, ETMR patients have dismal survival. Understanding the unique biology of these tumors has provided new insights towards novel therapeutic targets.

Histopathologic and Molecular Features of Central Nervous System Embryonal Tumors for Integrated Diagnosis Reporting

Embryonal tumors of the pediatric central nervous system are challenging clinically and diagnostically. These tumors are aggressive, and patients often have poor outcomes even with intense therapy. Proper tumor classification is essential to patient care, and this process has undergone significant changes with the World Health Organization recommending histopathologic and molecular features be integrated in diagnostic reporting. This has especially impacted the workup of embryonal tumors because molecular testing has resulted in the identification of clinically relevant tumor subgroups and new entities. This review summarizes recent developments and provides a framework to workup embryonal tumors in diagnostic practice.

Transcriptomic Analysis Revealed an Emerging Role of Alternative Splicing in Embryonal Tumor with Multilayered Rosettes

Embryonal tumor with multilayered rosettes (ETMR) is an aggressive and rare pediatric embryonal brain tumor. Amplification of C19MC microRNA cluster and expression of LIN28 are distinctive features of ETMR. Despite the increasing efforts to decipher ETMR, the biology remains poorly understood. To date, the role of aberrant alternative splicing in ETMR has not been thoroughly investigated. In the current study, a comprehensive analysis was performed on published unprocessed RNA-seq reads of tissue-matched ETMR and fetal controls datasets. Gene expression was quantified in samples using Kallisto/sleuth pipeline. For the alternative splicing analysis, STAR, SplAdder and rMATS were used. Functional enrichment analysis was subsequently performed using Metascape. The expression analysis identified a total of 3622 differentially expressed genes (DEGs) between ETMR and fetal controls while 1627 genes showed differential alternative splicing patterns. Interestingly, genes with significant alternative splicing events in ETMR were identified to be involved in signaling pathways such as ErbB, mTOR and MAPK pathways as well as ubiquitin-mediated proteolysis, cell cycle and autophagy. Moreover, up-regulated DEGs with alternative splicing events were involved in important biological processes including nuclear transport, regulation of cell cycle and regulation of Wnt signaling pathway. These findings highlight the role of aberrant alternative splicing in shaping the ETMR tumor landscape, and the identified pathways constitute potential therapeutic targets.

ETMR: a tumor entity in its infancy

Embryonal tumor with Multilayered Rosettes (ETMR) is a relatively rare but typically deadly type of brain tumor that occurs mostly in infants. Since the discovery of the characteristic chromosome 19 miRNA cluster (C19MC) amplification a decade ago, the methods for diagnosing this entity have improved and many new insights in the molecular landscape of ETMRs have been acquired. All ETMRs, despite their highly heterogeneous histology, are characterized by specific high expression of the RNA-binding protein LIN28A, which is, therefore, often used as a diagnostic marker for these tumors. ETMRs have few recurrent genetic aberrations, mainly affecting the miRNA pathway and including amplification of C19MC (embryonal tumor with multilayered rosettes, C19MC-altered) and mutually exclusive biallelic DICER1 mutations of which the first hit is typically inherited through the germline (embryonal tumor with multilayered rosettes, DICER1-altered). Identification of downstream pathways affected by the deregulated miRNA machinery has led to several proposed potential therapeutical vulnerabilities including targeting the WNT, SHH, or mTOR pathways, MYCN or chromosomal instability. However, despite those findings, treatment outcomes have only marginally improved, since the initial description of this tumor entity. Many patients do not survive longer than a year after diagnosis and the 5-year overall survival rate is still lower than 30%. Thus, there is an urgent need to translate the new insights in ETMR biology into more effective treatments. Here, we present an overview of clinical and molecular characteristics of ETMRs and the current progress on potential targeted therapies.

Pediatric embryonal brain tumors in the molecular era

Introduction: Embryonal brain tumors (EBTs) are highly aggressive malignancies predominantly affecting children. They include medulloblastoma (MB), atypical rhabdoid/teratoid tumors (ATRT), pineoblastoma (PB), embryonal tumor multiple rosettes (ETMR)/C19MC-altered tumors, and newly recognized embryonal tumors with FOXR2 activation or BCOR alteration.Areas covered: This review will provide a comprehensive overview and updated of the literature on each of these EBTs. The evolution from location- and histopathology-based diagnosis to more specific and robust molecular-based classification schemes, as well as treatment modalities, will be discussed.Expert commentary: The subgrouping of EBTs with multi-omic profiling has had important implications for risk stratification and discovery of targetable driver pathways. However, these innovations are unlikely to significantly improve survival among high-risk patients until robust preclinical studies are conducted, followed by validation in biology-informed clinical trials.

The molecular landscape of ETMR at diagnosis and relapse

Embryonal tumours with multilayered rosettes (ETMRs) are aggressive paediatric embryonal brain tumours with a universally poor prognosis1. Here we collected 193 primary ETMRs and 23 matched relapse samples to investigate the genomic landscape of this distinct tumour type. We found that patients with tumours in which the proposed driver C19MC2-4 was not amplified frequently had germline mutations in DICER1 or other microRNA-related aberrations such as somatic amplification of miR-17-92 (also known as MIR17HG). Whole-genome sequencing revealed that tumours had an overall low recurrence of single-nucleotide variants (SNVs), but showed prevalent genomic instability caused by widespread occurrence of R-loop structures. We show that R-loop-associated chromosomal instability can be induced by the loss of DICER1 function. Comparison of primary tumours and matched relapse samples showed a strong conservation of structural variants, but low conservation of SNVs. Moreover, many newly acquired SNVs are associated with a mutational signature related to cisplatin treatment. Finally, we show that targeting R-loops with topoisomerase and PARP inhibitors might be an effective treatment strategy for this deadly disease.

Targeted radioimmunotherapy for embryonal tumor with multilayered rosettes

PURPOSE

We explored the use of intraventricular ¹³¹I-Omburtamab targeting B7-H3 in patients with ETMR.

METHODS

Patients were enrolled in an IRB approved, phase 1, 3 + 3 dose escalation trial. Patients with CNS disease expressing the antibody target antigen B7-H3 were eligible. We report on a cohort of three patients with ETMR who were enrolled on the study. Three symptomatic children (ages 14 months, 3 and 3.5 years) had large parietal masses confirmed to be B7-H3-reactive ETMR. Patients received 2 mCi ¹³¹I-Omburtamab as a tracer followed by one or two therapeutic ¹³¹I-Omburtamab injections. Dosimetry was based on serial CSF, blood samplings and region of interest (ROI) on nuclear scans. Brain and spine MRIs and CSF cytology were done at baseline, 5 weeks after ¹³¹I-Omburtamab, and approximately every 3 months thereafter. Acute toxicities and survival were noted.

RESULTS

Patients received surgery, focal radiation, and high dose chemotherapy. Patients 1 and 2 received ¹³¹I-Omburtamab (80 and 53 mCi, respectively). Patient 3 had a local recurrence prior to ¹³¹I-Omburtamab treated with surgery, external beam radiation, chemotherapy, then ¹³¹I-Omburtamab (36 mCi). ¹³¹I-Omburtamab was well-tolerated. Mean dose delivered by ¹³¹I-Omburtamab was 68.4 cGy/mCi to CSF and 1.95 cGy/mCi to blood. Mean ROI doses were 230.4 (ventricular) and 58.2 (spinal) cGy/mCi. Patients 1 and 2 remain in remission 6.8 years and 2.3 years after diagnosis, respectively; patient 3 died of progressive disease 7 months after therapy (2 years after diagnosis).

CONCLUSIONS

¹³¹I-Omburtamab appears safe with favorable dosimetry therapeutic index. When used as consolidation following surgery and chemoradiation therapy, ¹³¹I-Omburtamab may have therapeutic benefit for patients with ETMR.

Embryonal tumor with multilayered rosettes: illustrative case and review of the literature

BACKGROUND

Embryonal tumor with multilayered rosettes (ETMR) is a very rare entity and has seldom been reported. It has been newly defined tumor entity included in the latest update (revised fourth edition) of WHO 2016 Classification of Tumors of the Central Nervous System which portends a uniform dismal prognosis and survival even with the best of multimodality approaches.

ILLUSTRATIVE CASE

This report documents the presentation of a 2-year-old girl with voluminous intracranial ETMR in the right parieto-occipital region. We describe clinical diagnosis, histological aspects, radiological features, and current management of this very aggressive tumor.

CONCLUSION

Pediatric intracranial ETMR is a highly aggressive neoplasm, and it should be considered in the differential diagnosis of pediatric brain tumors.

Radiation for ETMR: Literature review and case series of patients treated with proton therapy

Background and purpose

Embryonal tumors with multilayered rosettes (ETMRs) are aggressive tumors that typically occur in young children. Radiation is often deferred or delayed for these patients due to late effects; proton therapy may mitigate some of these concerns. This study reviews the role of radiation in ETMR and describes initial results with proton therapy.

Materials and methods

Records of patients with embryonal tumor with abundant neuropil and true rosettes (ETANTR), medulloepithelioma (MEP), and ependymoblastoma (EPL) treated with proton therapy at our institution were retrospectively reviewed. A literature review of cases of CNS ETANTR, MEP, and EPL published since 1990 was also conducted.

Results

Seven patients were treated with proton therapy. Their median age at diagnosis was 33 months (range 10-57 months) and their median age at radiation start was 42 months (range 17-58 months). Their median overall survival (OS) was 16 months (range 8-64 months), with three patients surviving 36 months or longer. Five patients had disease progression prior to starting radiation; all 5 of these patients failed in the tumor bed. A search of the literature identified 204 cases of ETMR with a median OS of 10 months (range 0.03-161 months). Median OS of 18 long-term survivors (≥36 months) in the literature was 77 months (range 37-184 months). Of these 18 long-term survivors, 17 (94%) received radiotherapy as part of their initial treatment; 14 of them were treated with craniospinal irradiation.

Conclusions

Outcomes of patients with ETMR treated with proton therapy are encouraging compared to historical results. Further study of this rare tumor is warranted to better define the role of radiotherapy.

Embryonal Tumors of the Central Nervous System: From the Radiologic Pathology Archives

Embryonal tumors of the central nervous system (CNS) are highly malignant undifferentiated or poorly differentiated tumors of neuroepithelial origin and have been defined as a category in the World Health Organization (WHO) classification since the first edition of the "Blue Book" in 1979. This category has evolved over time to reflect our ever-improving understanding of tumor biology and behavior. With the most recent update in 2016, many previous histologic diagnoses incorporate molecular parameters for the first time (genetically defined entities). While medulloblastoma and atypical teratoid/rhabdoid tumor are familiar carryovers from the 2007 CNS WHO classification, there are major changes to the embryonal tumor category: for example, elimination of the term CNS primitive neuroectodermal tumor and addition of a new genetically defined entity, embryonal tumor with multilayered rosettes, C19MC-altered. The purpose of this article is to discuss both the radiologic-pathologic features of CNS embryonal tumors and the new molecularly defined types/subtypes that will become the standard classification/terminology for future diagnoses and tumor research.

Extracranial extra-CNS spread of embryonal tumor with multilayered rosettes (ETMR): case series and systematic review

BACKGROUND

Embryonal tumors with multilayered rosettes (ETMR) is a rare variant of embryonal tumor of infancy with nearly 200 cases reported in the literature. Leptomeningeal spread of this tumor is well known; however, extracranial metastasis has been sparsely reported in the literature.

METHODS

Our study was divided into two sections: (1) We conducted a retrospective review of our patient series of ETMR and screened for patients with evidence of ETMR over the last 10 years 2007-2017 at a single tertiary referral pediatric hospital, and (2) we conducted a systematic review according to PRISMA guidelines of all reported cases of ETMR to determine the incidence of extracranial metastasis and treatment paradigms.

RESULTS

Here we report three cases of extracranial non-CNS spread of ETMR and conduct a systematic review of ETMR to improve our understanding of ETMR metastases and treatment paradigms. In our systematic review (n = 204), median overall survival was less than 1 year with 44.1% children surviving over 1 year. Previously, only five cases of extracranial metastasis of ETMR have been reported.

CONCLUSIONS

Our case series (n = 3) and review demonstrate that these tumors may behave like soft tissue sarcomas and may be susceptible to tumor seeding through surgical manipulation or by CSF (ventriculoperitoneal shunt). Surgery for tumor recurrence may offer an improved local disease control, but preventative measures such as meticulous surgical resection may be necessary to reduce intraoperative contamination.

Embryonal tumor with multilayered rosettes, C19MC-altered: Report of an extremely rare malignant pediatric central nervous system neoplasm

The 2016 update of the WHO Classification of Tumours of the Central Nervous System has redefined a number of tumors. Embryonal tumor with multilayered rosettes, C19MC-altered is one such tumor entity which has been newly defined on the basis of a characteristic molecular alteration. We report, to our knowledge, the first case of this rare pediatric brain neoplasm in the Pakistani population. An 8-month-old girl was presented with vomiting and left-sided ptosis, and magnetic resonance imaging scan showed a cerebellar tumor. Histologically, a highly cellular population of primitive cells was seen alternating with hypocellular neuropil-rich regions containing multilayered true rosettes and cells with glial and neuronal differentiation. Amplification of 19q13. 42 chromosome region on fluorescence in situ hybridization analysis confirmed the diagnosis. Post-operative radiological examination revealed widespread central nervous system involvement. Adjuvant treatment was not offered due to complications. Patient expired a week after diagnosis.

LIN28A, a sensitive immunohistochemical marker for Embryonal Tumor with Multilayered Rosettes (ETMR), is also positive in a subset of Atypical Teratoid/Rhabdoid Tumor (AT/RT)

INTRODUCTION

CNS embryonal tumors comprise a group of highly malignant neoplasms with a wide spectrum of histomorphological entities that includes Medulloblastoma (MB), Atypical Teratoid/Rhabdoid Tumor (AT/RT), Neuroblastoma (NB), Ganglioneuroblastoma (GNB), Embryonal Tumor with Multilayered Rosettes (ETMR), and the embryonal tumor-Not Otherwise Specified (NOS). The entity ETMR includes previously described histopathologic patterns-Embryonal Tumor with Abundant Neuropil and True Rosettes (ETANTR), Ependymoblastoma (EBL), and Medulloepithelioma (MEPL). Based on the histopathological similarities (multilayered rosettes) among ETANTR, EBL, and MEPL, as well as uniform clinical behavior and common molecular genetic characteristics, the WHO revision has created a new entity, "ETMR." Immunoreactivity of LIN28A has been identified as a sensitive tool for the diagnosis of this entity. Since there is a paucity of literature regarding immunoreactivity of LIN28A across all embryonal CNS tumors, the present study was undertaken.

MATERIALS AND METHODS

During the 5-year study period (2012 to 2016), all the embryonal tumors (MB, AT/RT, other embryonal tumors-ETANTR, MEPL, PNET) that had been earlier diagnosed in the department of neuropathology (cases operated in our institute as well as received as referral) were reviewed. The archived Hematoxylin and Eosin (H&E) and the available immunohistochemistry (IHC) sections were studied. Further, for the other embryonal tumors where the paraffin blocks were available, an extended panel of IHC was performed for confirming the diagnosis of embryonal tumor and only confirmed cases were included in the study. The demographic details of the study cohort were noted. IHC for LIN28A was performed on conventional sections.

RESULTS

A total of 396 cases of embryonal tumors including 302 MB, 72 AT/RT, and 22 other embryonal tumors were diagnosed during the study period. Among these, 80 MB, 35 AT/RT, 4 ETANTR, 1 MEPL, 4 NB, 2 GNB, and 1 CNS embryonal tumor-NOS (total-127) were included for the study. LIN28A immunoreactivity was absent in all MB, GNB, NB, and CNS embryonal tumors-NOS whereas all cases of ETMR (4 ETANTR, 1 MEPL) and 8/35 (23%) of AT/RT showed immunopositivity for LIN28A, which was patchy and distinct in most of the cases of ETMR.

CONCLUSION

Our study reiterates that LIN28A is a sensitive IHC marker for the diagnosis of ETMR. We also show that among CNS embryonal tumors, LIN28A is not specific to ETMRs and such immunoreactivity can also be seen in a proportion of AT/RTs.

Rare Primary Central Nervous System Tumors Encountered in Pediatrics

As part of the special issue on Pediatric Neuro-Oncology, this article will focus on 4 of the rarer tumors in this spectrum, including atypical teratoid rhabdoid tumors, embryonal tumors with multilayered rosettes, choroid plexus tumors, and pleomorphic xanthoastrocytoma. Incidence and current understanding of the molecular pathogenesis of these tumors are discussed, and avenues of therapy both current and prospective are explored.

New Brain Tumor Entities Emerge from Molecular Classification of CNS-PNETs

Primitive neuroectodermal tumors of the central nervous system (CNS-PNETs) are highly aggressive, poorly differentiated embryonal tumors occurring predominantly in young children but also affecting adolescents and adults. Herein, we demonstrate that a significant proportion of institutionally diagnosed CNS-PNETs display molecular profiles indistinguishable from those of various other well-defined CNS tumor entities, facilitating diagnosis and appropriate therapy for patients with these tumors. From the remaining fraction of CNS-PNETs, we identify four new CNS tumor entities, each associated with a recurrent genetic alteration and distinct histopathological and clinical features. These new molecular entities, designated "CNS neuroblastoma with FOXR2 activation (CNS NB-FOXR2)," "CNS Ewing sarcoma family tumor with CIC alteration (CNS EFT-CIC)," "CNS high-grade neuroepithelial tumor with MN1 alteration (CNS HGNET-MN1)," and "CNS high-grade neuroepithelial tumor with BCOR alteration (CNS HGNET-BCOR)," will enable meaningful clinical trials and the development of therapeutic strategies for patients affected by poorly differentiated CNS tumors.

Embryonal tumors with multilayered rosettes in children: the SFCE experience

PURPOSES

The purpose of this study was to retrospectively study embryonal tumors with multilayered rosettes (ETMR), a rare new entity that gathers ETAN-TR (embryonal tumor with abundant neuropil and true rosettes), ependymoblastomas, and medulloepitheliomas, in order to improve their descriptions and try to better define therapeutic modalities.

METHODS

Patients with ETMR, ETAN-TR, ependymoblastoma, and medulloepithelioma treated in SFCE centres (Société Française de lutte contre les Cancers et les leucémies de l'Enfant et de l'adolescent) since 2000 were collected. Data were retrieved from clinical charts.

RESULTS

Thirty-eight patients were included in the analysis. Seventeen had an ETAN-TR, 13 had a medulloepithelioma, and 8 had an ETMR. No ependymoblastoma was included. The median age at diagnosis was 31 months (range, 2.8-141 months). The predominant tumor location was supratentorial (66%); 18.4% patients had metastatic lesion. LIN28A expression was positive in 11/11 patients. Amplification of the locus 19q13.42 was positive in 10/12 patients. Thirty patients were treated according to the primitive neuroectodermal tumors of high risk (PNET-HR) protocol. The median time of follow-up was 0.9 years (range 0.1 to 15.3 years). The 1-year event-free survival (EFS) and overall survival (OS) were, respectively, 36% CI 95% (23-55) and 45% CI 95% (31-64). On multivariate analysis, complete surgical resection, radiotherapy, and high-dose chemotherapy were associated with a better overall survival with a relative risk of, respectively, 7.9 CI 95% (2.6-23.5) p < 0.0002, 41.8 CI 95% (9.4-186) p < 0.0001, and 3.5 CI 95% (1.3-9.5) p = 0.012.

CONCLUSION

Prognosis of ETMR remains dismal despite multimodal therapy. LIN28A immunostaining and 19q13.42 amplification should be systematically done to secure the diagnosis. Complete surgical resection, radiotherapy, and high-dose chemotherapy are associated with better outcome.

Embryonal Tumor With Abundant Neuropil and True Rosettes: A Distinct Immunohistochemical Pattern

Embryonal tumors with abundant neuropil and true rosettes (ETANTR) are rare pediatric embryonal neoplasms that combine features of neuroblastoma and ependymoblastoma. We report a distinct immunohistochemical-staining pattern of ETANTR in a 12-month-old baby who presented with a supratentorial mass. The tumor exhibited a characteristic biphasic pattern of neuropil-rich areas and patchy cellular neuropil-poor areas. The neoplastic cells in neuropil-rich areas are diffusely immunoreactive to chromogranin A, synaptophysin, neurofilament, and CD56, but show no immunoreactivity to nestin, SOX2, WT-1, β-catenin, and vimentin. While the cells in neuropil-poor areas, including ependymoblastic and Flexner-Wintersteiner rosettes, are diffusely immunoreactive to nestin, SOX2, WT-1, β-catenin, and vimentin but show no immunoreactivity to chromogranin A, synaptophysin, neurofilament, and CD56. Ependymoblastic rosettes show luminal membranous immunoreactivity to EMA. We believe that ETANTR has a distinct histologic and immunohistochemical pattern supporting the embryonal origin of this tumor with divergent neuroblastic and primitive glial differentiation.

Embryonal tumor with multilayered rosettes of the fourth ventricle: case report

Embryonal tumor with multilayered rosettes (ETMR) is a recently described pathological entity. These primitive central nervous system tumors harbor amplification of the 19q13.42 locus and resultant overexpression of the LIN28A protein. Although the WHO currently recognizes 3 distinct histopathological entities-embryonal tumor with abundant neuropil and true rosettes (ETANTR), ependymoblastoma, and medulloepithelioma-recent studies indicate that these tumors have a common molecular profile and clinical course and that they are now classified as a single entity. Here the authors present a case of ETMR located in the fourth ventricle in a 12-month-old boy. The histopathology featured areas of neuropil-like stroma and highly cellular foci with characteristic multilayered rosettes. The authors discuss the clinical, radiological, and histopathological findings in this case and compare them with data in previously published cases in the literature. A review of studies assessing the molecular mechanisms underlying these tumors is also presented.

Embryonal tumor with abundant neuropil and true rosettes in the brainstem: case report

Embryonal tumor with abundant neuropil and true rosettes (ETANTR) is rarely seen in the brainstem, and there are few case reports of brainstem ETANTR in the literature. Accordingly, the characteristics and the role of surgical treatment of this rare entity remain unclear. The authors present a case of brainstem ETANTR involving a 33-month-old boy along with a review of the literature and discuss the role of surgical removal in the treatment of this entity. In the authors' case, the tumor was surgically treated with subtotal resection, which resulted in improvement of the patient's preoperative symptoms. Chemotherapy was initiated but did not appear to be effective, radiotherapy was declined, and the boy died 6 months after the operation. Based on their analysis of 10 previously reported cases and their own case, the authors conclude that, with respect to survival, surgery may be beneficial even in cases of ETANTR in the brainstem. They note, however, that further studies with a large number of cases are needed to validate the role of surgical treatment in brainstem ETANTR.

[Molecular methods in diagnosis of poorly differentiated malignant brain tumors in children]

The histological diagnosis of malignant brain tumors in children is a complex process. In some cases, glioblastoma, primitive neuroectodermal tumor of the central nervous system, and atypical teratoid/rhabdoid tumor have a histological type similar to that of small blue round cell malignant tumor. Despite the similar histology, biological properties and approaches to treatment, these neoplasms are completely different and require their own treatment protocols. We retrospectively reviewed the most malignant types of childhood tumors and analyzed our own experience to propose a diagnostic algorithm for intracerebral small blue round cell malignant tumors in children based on the use of immunohistochemistry and fluorescence in situ hybridization.

Systematic comparison of MRI findings in pediatric ependymoblastoma with ependymoma and CNS primitive neuroectodermal tumor not otherwise specified

BACKGROUND

Ependymoblastoma (EBL), ependymoma (EP), and primitive neuroectodermal tumors of the central nervous system not otherwise specified (CNS-PNET NOS) are pediatric brain tumors that can be differentiated by histopathology in the clinical setting. Recently, we described specific MRI features of EBL. In this study, we compare standardized MRI characteristics of EBL with EP and CNS-PNET NOS in a series comprising 22 patients in each group.

METHODS

All 66 centrally reviewed cases were obtained from the database of the German multicenter HIT trials. We systematically analyzed the initial MRI scans at diagnosis according to standardized criteria, and paired comparison was performed for EBL and EP, as well as for EBL and CNS-PNET NOS.

RESULTS

We found differences between EBL and EP regarding age at diagnosis, MR signal intensity, tumor margin and surrounding edema, presence and size of cysts, and contrast enhancement pattern. Although MRI appearance of EBL shares many features with CNS-PNET NOS, we revealed significant differences in terms of age at diagnosis, tumor volume and localization, tumor margins, edema, and contrast enhancement.

CONCLUSION

This is the first study that systematically compares multiple parameters of MRI in pediatric EBL with findings in EP and CNS-PNET NOS. Although a definite differentiation by means of MRI alone might not be feasible in the individual case, we identify significant differences between these tumor entities.

High-dose Chemotherapy With Autologous Stem Cell Rescue in Saudi Children Less Than 3 Years of Age With Embryonal Brain Tumors

High-dose chemotherapy with autologous stem cell rescue (HDC/ASCR) has been used in children under the age of 3 years with embryonal brain tumors to avoid or delay the use of radiation. We reviewed the medical records of 10 Saudi children less than 3 years of age with embryonal brain tumors who underwent HDC/ASCR. All 10 patients underwent surgical resection followed by 3 to 5 cycles of induction chemotherapy and 1 to 3 cycles of HDC/ASCR using carboplatin and thiotepa. Isotretinoin was used as a maintenance therapy in 4 patients. Five patients had medulloblastoma, 3 had atypical teratoid/rhabdoid tumors, 1 had an embryonal tumor with abundant neuropil and true rosettes, and 1 had pineoblastoma. The median age of the patients was 1.9 years. A total of 19 HDC/ASCR procedures were performed. Radiotherapy (RT) was administered to 5 patients after HDC/ASCR and as a salvage therapy in 1 patient. The progression-free survival rate was 50% at 1 year and at 2 years, with a median follow-up of 24 months. All 5 patients with medulloblastoma are still alive without evidence of disease, but the other patients died secondary to tumor progression. This experience suggests that strategies combining myeloablative chemotherapy and autologous stem cell rescue appear to be feasible for children with embryonal brain tumors in the Middle East.

Central nervous system tumors in chinese children under the age of 3: a population study

The management of central nervous system tumors in children below the age of 3 years represents a special challenge to pediatric oncologists with distinctive epidemiology, treatment considerations, and prognosis. Population-based epidemiological data on this particular patient group is lacking in Chinese. We reviewed the population-based pediatric tumor registry in Hong Kong between 1999 and 2011. Eighty-one children with primary central nervous system tumors from 0 to 3 years of age were identified (annual incidence: 4.16 cases per 100,000). Forty-one (50.6%) were male and the mean duration of follow-up was 94 months (±8.1). Primary tumors were infratentorial in 43 (53.1%). The tumor types in decreasing frequency were astrocytoma (n=17), medulloblastoma (n=16), ependymoma (n=13), choroid plexus tumor (n=7), primitive neuroectodermal tumor (n=7), atypical teratoid rhabdoid tumor (n=6), germ cell tumor (GCT, n=5), craniopharyngioma (n=4), and ganglioglioma (n=3). Three patients presented antenatally. Treatment included surgery in 82.7%, chemotherapy in 50.6%, and radiotherapy in 25.9%. There were 29 deaths (35.8%) and 19 relapses (23.5%) during the review period with the 1-year overall survival (OS), 5-year OS, 1-year event-free survival (EFS), and 5-year EFS being 79.4% (±4.6), 63.5% (±5.9), 68.9% (±5.3), and 52.5% (±5.9), respectively. Significantly better OS and EFS were observed in patients who received gross total resection, but those with high-grade tumors, antenatal diagnosis, or atypical teratoid rhabdoid tumor/primitive neuroectodermal tumor had worse outcome. Survival did not differ with age. Comparison with statistics from other studies revealed higher rates of embryonal tumor, GCT, and craniopharyngioma in Hong Kong Chinese. Disease outcome appeared to be better in our cohort comparing to previous reports probably due to the higher proportion of GCT locally.

Rare pathologies in the posterior third ventricular region in children: case series and review

Tumors of the pineal region in children often belong to 2 categories, namely germ cell tumors and pineal parenchymal tumors. Very rare pathologies have previously been reported in this region. Most of these tumors may be similar radiologically, while their management differs. The present series reports 2 children with pineal region tumors, each one being a rare pathological entity by itself, namely an embryonal tumor with abundant neuropil and true rosettes (ETANTR) and a rosette-forming glioneuronal tumor (RGNT). Very few such cases in each pathology have been reported in the literature for the pediatric age group up to now. Our series consists of 2 children, both presenting with a raised intracranial pressure of short duration. Imaging revealed lesions in the pineal region with similar radiological features. Both ETANTR and RGNT demonstrated mild enhancement. The 2 patients underwent surgical decompression either by Poppen's approach (n = 1) or a supracerebellar infratentorial approach (n = 1). The patient with ETANTR was advised radiotherapy, while the child with RGNT was advised a regular follow-up. This series presents some rare pathologies which can occur in the posterior third ventricular region with similar radiological features. Management differs based on the histology of the case.

Practical molecular pathology and histopathology of embryonal tumors

There have been significant improvements in understanding of embryonal tumors of the central nervous system (CNS) in recent years. These advances are most likely to influence the diagnostic algorithms and methodology currently proposed by the World Health Organization (WHO) classification scheme. Molecular evidence suggests that the tumors presumed to be specific entities within the CNS/primitive neuroectodermal tumors spectrum are likely to be reclassified. All these developments compel reassessing current status and expectations from the upcoming WHO classification efforts. This review provides a synopsis of current developments and a practical algorithm for the work-up of these tumors in practice.

MRI characteristics of ependymoblastoma: results from 22 centrally reviewed cases

BACKGROUND AND PURPOSE

Ependymoblastoma is a malignant embryonal tumor that develops in early childhood and has a dismal prognosis. Categorized by the World Health Organization as a subgroup of CNS-primitive neuroectodermal tumor, ependymoblastoma is histologically defined by "ependymoblastic rosettes." Because it is so rare, little is known about specific MR imaging characteristics of ependymoblastoma. We systematically analyzed and discussed MR imaging features of ependymoblastoma in a series of 22 consecutive patients.

MATERIALS AND METHODS

Ependymoblastoma cases were obtained from the database of the German multicenter HIT trials between 2002 and 2013. All cases within this study were centrally reviewed for histopathology, MR imaging findings, and multimodal therapy. For systematic analysis of initial MR imaging scans at diagnosis, we applied standardized criteria for reference image evaluation of pediatric brain tumors.

RESULTS

Ependymoblastomas are large tumors with well-defined tumor margins, iso- to hyperintense signal on T2WI, and diffusion restriction. Contrast enhancement is variable, with a tendency to mild or moderate enhancement. Subarachnoid spread is common in ependymoblastoma but can be absent initially. There was a male preponderance (1.75:1 ratio) for ependymoblastoma in our cohort. Mean age at diagnosis was 2.1 years.

CONCLUSIONS

With this study, we add the largest case collection to the limited published database of MR imaging findings in ependymoblastoma, together with epidemiologic data. However, future studies are needed to systematically compare MR imaging findings of ependymoblastoma with other CNS-primitive neuroectodermal tumors and ependymoma, to delineate imaging criteria that might help distinguish these pediatric brain tumor entities.

Embryonal tumor with abundant neuropil and true rosettes with only one structure suggestive of an ependymoblastic rosette

Embryonal tumor with abundant neuropil and true rosettes (ETANTR) is a very aggressive embryonal central nervous system (CNS) tumor, histologically featuring ependymoblastic rosettes and neuronal differentiation in a neuropil-like background. 19q13.42 amplification was identified in ETANTR and epndymoblastoma, suggesting that these tumors constitute a single entity, called embryonal tumor with multilayered rosettes (ETMR). Here, we report a case involving a 2-year-old boy with a pontine embryonal tumor composed of clusters of poorly differentiated neuroepithelial cells, and smaller neuroblastic/neurocytic cells in a fibrillary and paucicellular neuropil-like matrix, where clear ependymoblastic rosettes were not detected but only one structure suggestive of an ependymoblastic multilayered rosette was found. Fluorescence in situ hybridazation analysis revealed 19q13.42 amplification, supporting the diagnosis of ETANTR. This report indicates that rare ependymoblasic rosettes found in embryonal tumors, which are otherwise CNS primitive neuroectodermal tumors or medulloblastomas, are significant for considering the examination of 19q13.42 amplification to confirm the diagnosis of ETMR.