Central nervous system primitive neuroectodermal tumors: a clinicopathologic and genetic study of 33 cases

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%.

Spectrum of paired-like homeobox 2b immunoexpression in pediatric brain tumors with embryonal morphology

Paired‐like homeobox 2b (PHOX2B) is an established immunomarker for peripheral neuroblastoma and autonomic nervous system cells. We aimed to evaluate the utility of PHOX2B immunostaining in central nervous system (CNS) tumors with embryonal morphology. Fifty‐one tumors were stained with PHOX2B and submitted for whole slide image analysis: 35 CNS tumors with embryonal morphology (31 CNS embryonal tumors and four gliomas); and 16 peripheral neuroblastomas were included for comparison. Diffuse nuclear immunopositivity was observed in all (16/16) neuroblastomas (primary and metastatic). Among CNS embryonal tumors, focal immunoreactivity for PHOX2B was observed in most (5/7) embryonal tumors with multilayered rosettes (ETMR) and a single high‐grade neuroepithelial tumor (HGNET) with PLAGL2 amplification; the remaining 27 CNS tumors were essentially immunonegative (<0.05% positive). Among ETMR, PHOX2B expression was observed in a small overall proportion (0.04%–4.94%) of neoplastic cells but focally reached up to 39% in 1 mm ‘hot spot’ areas. In the PLAGL2‐amplified case, 0.09% of the total neoplastic population was immunoreactive, with 0.53% in the ‘hot spot’ area. Care should be taken in interpreting PHOX2B immunopositivity in a differential diagnosis that includes metastatic neuroblastoma and CNS tumors; focal or patchy expression should not be considered definitively diagnostic of metastatic peripheral neuroblastoma.

GEM-IL: A highly responsive fluorescent lactate indicator

Lactate metabolism has been shown to have increasingly important implications in cellular functions as well as in the development and pathophysiology of disease. The various roles as a signaling molecule and metabolite have led to interest in establishing a new method to detect lactate changes in live cells. Here we report our development of a genetically encoded metabolic indicator specifically for probing lactate (GEM-IL) based on superfolder fluorescent proteins and mutagenesis. With improvements in its design, specificity, and sensitivity, GEM-IL allows new applications compared with the previous lactate indicators, Laconic and Green Lindoblum. We demonstrate the functionality of GEM-IL to detect differences in lactate changes in human oncogenic neural progenitor cells and mouse primary ventricular myocytes. The development and application of GEM-IL show promise for enhancing our understanding of lactate dynamics and roles.

An efficient and novel treatment regimen including temozolomide for medulloblastoma: a case study

Background:

The central nervous system (CNS) embryonal tumour is a rare malignancy reported in adults and more commonly in children. The most available treatments may cause neurological dysfunctions requiring clinical attention.

Case presented:

A 29-year-old male was referred with ataxia and diplopia, and brain imaging revealed a posterior fossa lesion suggesting medulloblastoma. The tumour and related symptoms were notably alleviated following treatment with dexamethasone. Following the recurrence of tumour, a biopsy and pathology report, the diagnosis of desmoplastic/nodular medulloblastoma was confirmed. The patient underwent 18 fractions of 180 cGy spine and whole-brain radiation therapy (RT). In addition, 5400 cGy irradiation in 12 fractions was given to the posterior fossa together with 2 mg/m2 intravenous vincristine (VCR) weekly over 6 weeks. Following a 3-week break, the patient was scheduled to receive 150 mg/m2/day temozolomide for 5 days, 2 mg VCR and 65 mg/m2/day cisplatin every 3 weeks for 8 cycles.

Conclusion:

The patient gained survival benefit to date (60 months since diagnosis) with favourable life quality. The promising response in this one exemplary case study proposes that a combined chemotherapy regimen including temozolomide, vincristine and cisplatin is an effective treatment choice for CNS embryonal tumours following RT; however, the further evaluation and a randomised clinical trial are needed.

Primitive Neuroectodermal Tumor in a Child with Human Immunodeficiency Virus Infection: A Rare Association

Children with human immunodeficiency virus (HIV) infection are reported to have various malignancies, most common being Non-Hodgkin lymphoma. Despite higher risk of malignancies, brain tumors are infrequently described in these children. We report Primitive Neuroectodermal tumor (PNET) in a young boy with HIV infection. PNET has never been described in association with HIV infection. Though a causative association cannot be established, it does emphasize that with longer survivals on effective antiretroviral therapy, we may see a wide range of malignancies more frequently.

Imaging features of spinal atypical teratoid rhabdoid tumors in children

This study aims to analyze and summarize the imaging features of spinal atypical teratoid/rhabdoid tumors (AT/RT) in children.Imaging features in 8 children with spinal AT/RT confirmed by surgical pathology were retrospectively analyzed. All patients had underwent total spine 3.0 T magnetic resonance imaging (MRI) and 64-slice spiral computed tomography (CT). Among these 8 patients, head MR non-enhanced and spinal enhanced scanning was applied to 5 patients, while CT examination was applied to 3 patients.All 8 patients were characterized by cauda equina syndrome. The lesions of 7 patients were in the thoracolumbar spinal junction, while the lesion of the remaining patient was in the lumbar spine. Furthermore, among these patients, the lesions of 5 patients were limited to the intraspinal canal (1 lesion in the epidural space, and 4 lesions in the subdural space), while the lesions of 3 patients invaded the paravertebra (2 lesions in the epidural space and 1 lesion in the subdural space). Three or more spinal segments were invaded by tumors in 7 patients, while sacral canal was affected in 5 patients. All 8 patients experienced bleeding in the tumors. Enhanced MRI revealed meningeal enhancement in 6 patients, and bilateral nerve root enhancement in 4 patients. The masses in 3 patients brought damages to the intervertebral foramen or sacral pore. The lesion of 1 patient was featured by skip growth. One patient had total spinal metastasis and 3 had hydrocephalus. The masses in 2 patients had a slightly low density when detected by CT, and enhanced scanning revealed a mild to moderate enhancement.Spinal AR/TR had the following characteristics: children were characterized by cauda equina syndrome; the mass that invaded the thoracolumbar spinal junction and the extramedullary space of multiple segments grew along the spinal longitudinal axis; bleeding mass was revealed in MRI imaging; meninges, nerve root, and sacral canal metastases occurred. The gold standard for the definite diagnosis of AT/RT is biopsy combined with immunohistochemistry.

The case for DNA methylation based molecular profiling to improve diagnostic accuracy for central nervous system embryonal tumors (not otherwise specified) in adults

Central nervous system primitive neuro-ectodermal tumors (CNS-PNETs), have recently been re-classified in the most recent 2016 WHO Classification into a standby catch all category, "CNS Embryonal Tumor, not otherwise specified" (CNS embryonal tumor, NOS) based on epigenetic, biologic and histopathologic criteria. CNS embryonal tumors (NOS) are a rare, histologically and molecularly heterogeneous group of tumors that predominantly affect children, and occasionally adults. Diagnosis of this entity continues to be challenging and the ramifications of misdiagnosis of this aggressive class of brain tumors are significant. We report the case of a 45-year-old woman who was diagnosed with a central nervous system embryonal tumor (NOS) based on immunohistochemical analysis of the patient's tumor at diagnosis. However, later genome-wide methylation profiling of the diagnostic tumor undertaken to guide treatment, revealed characteristics most consistent with IDH-mutant astrocytoma. DNA sequencing and immunohistochemistry confirmed the presence of IDH1 and ATRX mutations resulting in a revised diagnosis of high-grade small cell astrocytoma, and the implementation of a less aggressive treatment regime tailored more appropriately to the patient's tumor type. This case highlights the inadequacy of histology alone for the diagnosis of brain tumours and the utility of methylation profiling and integrated genomic analysis for the diagnostic verification of adults with suspected CNS embryonal tumor (NOS), and is consistent with the increasing realization in the field that a combined diagnostic approach based on clinical, histopathological and molecular data is required to more accurately distinguish brain tumor subtypes and inform more effective therapy.

Stabilization of HIF-1α and HIF-2α, up-regulation of MYCC and accumulation of stabilized p53 constitute hallmarks of CNS-PNET animal model

Recently, we described a new animal model of CNS primitive neuroectodermal tumors (CNS-PNET), which was generated by orthotopic transplantation of human Radial Glial (RG) cells into NOD-SCID mice's brain sub-ventricular zone. In the current study we conducted comprehensive RNA-Seq analyses to gain insights on the mechanisms underlying tumorigenesis in this mouse model of CNS-PNET. Here we show that the RNA-Seq profiles derived from these tumors cluster with those reported for patients' PNETs. Moreover, we found that (i) stabilization of HIF-1α and HIF-2α, which are involved in mediation of the hypoxic responses in the majority of cell types, (ii) up-regulation of MYCC, a key onco-protein whose dysregulation occurs in ~70% of human tumors, and (iii) accumulation of stabilized p53, which is commonly altered in human cancers, constitute hallmarks of our tumor model, and might represent the basis for CNS-PNET tumorigenesis in this model. We discuss the possibility that these three events might be interconnected. These results indicate that our model may prove invaluable to uncover the molecular events leading to MYCC and TP53 alterations, which would be of broader interest considering their relevance to many human malignancies. Lastly, this mouse model might prove useful for drug screening targeting MYCC and related members of its protein interaction network.

Meningeal Ewing Sarcoma/Peripheral PNET: Clinicopathological, Immunohistochemical and FISH study of four cases

Meningeal Ewing Sarcoma (ES)/peripheral primitive neuroectodermal tumor (pPNET) is a rare diagnostically challenging small round cell tumor in the CNS. This study investigates the clinical pathological features of four cases of this tumor from archives of 6 years in our hospital. Patients were within the median age of 21.5 years and male to female ratio was 1:1. The tumors distributed at the supra-tentorial location, posterior fossa and lumbar vertebral canal, usually presenting as the dura-sited nodule or having close connection with the meninges within the cranium or vertebral canal. Histopathologically, small round undifferentiated tumor cells with hypercellularities, scant cytoplasm and inconspicuous nucleoli were observed, although some components such as atypical larger vesicular nuclei, prominent nucleoli of tumor cells, necrotic foci and mesenchymal collagen proliferation forming the lobular structure, were also appreciated. Immunohistochemally, tumor cells displayed membranous positivity of CD99 (4/4), nuclear positivity of FLI-1 (4/4) and NKX2.2 (4/4), negativity of EMA, GFAP and synaptophysin expression. The histochemical PAS staining showed weak positivity in one case. Fluorescence in situ hybridization (FISH) test using EWSR1 (22q12) dual color break apart rearrangement probe showed positive results in two cases. Results suggest that using a panel of immunohistochemical markers, including NKX2.2, CD99, FLI-1, EMA, GFAP and synaptophysin, combined with the supplementary EWSR1 FISH test, helps to define the diagnosis of meningeal ES/pPNET of CNS.

Revisiting Management of Pediatric Brain Tumors with New Molecular Insights

Pediatric central nervous system primitive neuro-ectodermal brain tumors (CNS-PNETs) are rare tumors with ill-defined biological features. In this issue of Cell, Sturm et al. used state-of-the-art methods to interrogate these tumors' biology. Their integrated molecular analyses led them to propose a new molecular classification, with four new entities identified, that should get oncologists' attention.

Malignant brainstem tumors in children, excluding diffuse intrinsic pontine gliomas

OBJECT Malignant tumors of the brainstem, excluding classic diffuse intrinsic pontine gliomas (DIPGs), are a very rare, heterogeneous group of neoplasms that have been infrequently described in the literature. In this paper, the authors present their experiences with treating these unique cancers. METHODS A retrospective chart review was conducted to identify eligible cases over a 15-year period. All tumors involving the pons were, by consensus, felt not to be DIPGs based on their neuroimaging features. Demographic information, pathological specimens, neuroimaging characteristics, surgical and nonsurgical management plans, and survival data were gathered for analysis. RESULTS Between January 2000 and December 2014, 29 patients were identified. The mean age at diagnosis was 8.4 years (range 2 months to 25 years), and 17 (59%) patients were male. The most common presenting signs and symptoms were cranial neuropathies (n = 24; 83%), hemiparesis (n = 12; 41%), and ataxia or gait disturbance (n = 10; 34%). There were 18 glial and 11 embryonal tumors. Of the glial tumors, 5 were radiation-induced and 1 was a malignant transformation of a previously known low-grade tumor. Surgical intervention consisted of biopsy alone in 12 patients and some degree of resection in another 15 patients. Two tumors were diagnosed postmortem. The median overall survival for all patients was 196 days (range 15 to 3999 days). There are currently 5 (17%) patients who are still alive: 1 with an anaplastic astrocytoma and the remaining with embryonal tumors. CONCLUSIONS In general, malignant non-DIPG tumors of the brainstem carry a poor prognosis. However, maximal cytoreductive surgery may be an option for select patients with focal tumors. Long-term survival is possible in patients with nonmetastatic embryonal tumors after multimodal treatment, most importantly maximal resection.

MYCN amplification predicts poor outcome for patients with supratentorial primitive neuroectodermal tumors of the central nervous system

BACKGROUND

Primitive neuroectodermal tumors of the central nervous system (CNS-PNETs) are a rare group of neoplasms occurring in the CNS that includes supratentorial CNS-PNETs, medulloepitheliomas, and ependymoblastomas. While ependymoblastomas frequently carry chromosome 19q13.41 amplification and show aggressive clinical behavior, the biological mechanisms and molecular alterations contributing to the pathogenesis of supratentorial CNS-PNETs remain poorly understood. Moreover, genetic alterations suitable for molecular risk stratification are undefined to date.

METHODS

In order to identify possible molecular markers, we performed multiplex ligation-dependent probe amplification (MLPA) and molecular inversion probe (MIP) analysis on DNA samples of 25 supratentorial CNS-PNETs (median age, 5.35 years; range, 2.41–17.28 years). Tumors with ependymoblastic rosettes (ependymoblastoma/ETANTR) and LIN28A positivity were excluded.

RESULTS

MLPA and MIP analysis revealed large losses of genomic material of chromosomes 3, 4, 5, and 13, while frequent gains affected chromosomes 1, 17, 19, 20, and 22. High copy number gains (amplifications) were found in particular at chromosomes 2p24.3 (MYCN, n = 6 cases) and 4q12 (n = 2 cases). Patients with tumors harboring 2p gain or MYCN amplification showed unfavorable overall survival (P = .003 and P = .001, respectively).These markers were independent of the presence of metastases, which was indeed a clinical factor associated with poor overall survival (P = .01) in this series.

CONCLUSIONS

In the era of the personalized neuro-oncology, the identification of these molecular prognostic markers associated with patient outcome may represent a significant step towards improved patient stratification and risk-adapted therapeutic strategies for patients suffering from supratentorial CNS-PNETs.

Clinical, Pathological, and Surgical Outcomes for Adult Pineoblastomas

INTRODUCTION

Pineoblastomas are uncommon primitive neuroectodermal tumors that occur mostly in children; they are exceedingly rare in adults. Few published reports have compared the various aspects of these tumors between adults and children.

METHODS

The authors report a series of 12 pineoblastomas in adults from 2 institutions over 24 years. The clinical, radiologic, and pathologic features and clinical outcomes were compared with previously reported cases in children and adults.

RESULTS

Patient age ranged from 24 to 81 years, and all but 1 patient exhibited symptoms of obstructive hydrocephalus. Three patients underwent gross total resection, and subtotal resection was performed in 3 patients. Diagnostic biopsy specimens were obtained in an additional 6 patients. Pathologically, the tumors had the classical morphologic and immunohistochemical features of pineoblastomas. Postoperatively, 10 patients received radiotherapy, and 5 patients received chemotherapy. Compared with previously reported cases, several differences were noted in clinical outcomes. Of the 12 patients, only 5 (42%) died of their disease (average length of survival, 118 months); 5 patients (42%) are alive with no evidence of disease (average length of follow-up, 92 months). One patient died of unrelated causes, and one was lost to follow-up. Patients with subtotal resections or diagnostic biopsies did not suffer a worse prognosis. Of the 9 patients with biopsy or subtotal resection, 4 are alive, 4 died of their disease, and 1 died of an unrelated hemorrhagic cerebral infarction.

CONCLUSIONS

Although this series is small, the data suggest that pineoblastomas in adults have a less aggressive clinical course than in children.

Atypical teratoid/ rhabdoid tumor, an immunohistochemical study of potential diagnostic and prognostic markers

Atypical teratoid/rhabdoid tumor (AT/RT) is a rare tumor of the CNS mostly seen in infants and is often associated with a dismal outcome. Despite the heterogeneous morphology and/or immunoprofile, its diagnosis nowadays relies on the negative INI-1/BAF47 nuclear immunostain in tumor cells. We aim to investigate a number of immunohistochemical antibodies as potential diagnostic and prognostic markers. All AT/RT cases in patients younger than 18 years of age were included. Demographics, clinical features and outcome were collected. Immunostains tested included SALL-4, OCT3/4, CD99, FLI-1, cyclin-D1, β-catenin, P53, P16, CDX2 and WT-1. Nineteen cases (10 males) were identified at our center between 2004-2013 with a median age of 24 months. Ten (52.6%) cases were supratentorial. Six (42.9%) cases showed metastasis at time of presentation. Chemotherapy was administered to 10 (62.5%) and radiotherapy to seven (43.8%). The median overall survival was 11 months. A single long-term survival of 104 months was identified. Pathologically, most cases showed an admixture of rhabdoid cells and/or small cells and/or pale cells in variable proportions. Of all tested antibodies, only positivity for FLI-1 was associated with improved survival (P = 0.0012), while positivity for cyclin-D1 showed a trend toward improved survival (P = 0.0547). CDX2 was positive only in the single long-term survival. Interestingly, two cases showed co-expression of CD99 and FLI-1, and some were positive for SALL-4. In conclusion, FLI-1 and cyclin-D1 are potential prognostic markers associated with better outcome. Occasional AT/RT cases might co-express CD99 and FLI-1 as well as SALL-4, a potential diagnostic pitfall with Ewing sarcoma/ primitive neuroectodermal tumors and germ cell tumors, respectively.

[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.

A Primary Primitive Neuroectodermal Tumor Arising from Left Subclavian Vein and Extending along Left Brachiocephalic Vein and Superior Vena Cava into Right Atrium

Primitive neuroectodermal tumor (PNET) is an extremely rare malignancy thought to be derived from fetal neuroectodermal precursor cells. It usually occurs in central and peripheral nervous system or soft tissue and bone, while intravenous or intracavitary PNET is considered as an extremely rare tumor. We reported a case of a 44-year-old woman who presented with the left unilateral facial and neck swelling. Magnetic resonance imaging revealed a tape-shaped solid mass within left subclavian vein, left brachiocephalic vein, superior vena cava, and right atrium; the proximal end proportion occupied almost the entire right atrium with a pedicle flip protruded into the right ventricle. Ultrasonography revealed an irregular hypoechnoic mass arising from the left subclavian vein, which extended along the left brachiocephalic vein and superior vena cava into the right atrium and up to the right ventricle. Positron emission tomography-computed tomography revealed several hypermetabolic thyroid nodules with no evidence of intravenous hyperactive lesion. The patient underwent tumor resection under cardiopulmonary bypass. At 15 days postoperatively, total thyroidectomy and resection of the left subclavian vein were simultaneously performed. The patient received chemotherapy and radiotherapy later. Histologically, the neoplasm displayed small, round, blue cells with hyperchromatic nuclei and scant cytoplasm. The neoplastic cells showed a strong immunopositivity for CD99, synaptophysin, CD56, CD57, and friend leukemia integration 1, thus confirming a diagnosis of the PNET. Histopathological examination of the thyroid showed papillary carcinoma. Thus, this PNET had no definitive organ or tissue of origin, which primarily originated from the left subclavian vein with tumor extension along the superior vena cava to the right ventricle.

The potential for epigenetic analysis of paediatric CNS tumours to improve diagnosis, treatment and prognosis

Tumours of central nervous system (CNS) origin are the second most prevalent group of cancers in children, yet account for the majority of childhood cancer-related deaths. Such tumours show diverse location, cell type of origin, disease course and long-term outcome, both across and within tumour types, making treatment problematic and contributing to the relatively modest progress in reducing mortality over recent decades. As technological advances begin to reveal the genetic landscape of all cancers, it is becoming increasingly clear that genetic disruption represents only one 'layer' of molecular disruption associated with disease aetiology. Obtaining a full understanding of tumour behaviour requires an understanding of the cellular and molecular pathways disrupted during tumourigenesis, particularly in relation to gene expression. The utility of such an approach has allowed stratification of cancers such as medulloblastoma into subgroups based on molecular features, with potential to refine risk prediction. Given that epigenetic disruption is a universal feature of all human cancers, it is logical to speculate that interrogating epigenetic marks may help to further define the molecular profile, and therefore the clinical trajectory, of tumours. An integrated approach to build a molecular 'signature' of individual tumours that incorporates traditional morphological and demographic information, genetic and transcriptome analysis, in addition to epigenomics (DNA methylation and non-coding RNA analysis), offers tremendous promise to (i) inform treatment approach, (ii) facilitate accurate early identification (preferably at diagnosis) of variable risk groups (both good and poor prognosis groups), and (iii) track disease progression in childhood CNS tumours.

Primary intracranial Ewing's sarcoma with unusual features

Pediatric primary "small round blue cell" tumors in the CNS represent several entities, some more common than others. Ewing sarcoma/peripheral primitive neuroectodermal tumor (ES/pPNET) is rare and must be distinguished from other tumors such as medulloblastoma [1, 2], atypical rhabdoid/teratoid tumor, ependymomal tumors, metastatic sarcomas, hematologic malignancies, and other mimics. Although therapy for ES/pPNET is effective, it brings severe side effects, including cardiac toxicity, making correct recognition important [3]. As small blue cell tumors look similar, diagnosis often depends on special stains, immunohistochemistry, and molecular techniques. While the combination of membranous immunohistochemical reactivity for CD99 with cytoplasmic glycogen provides effective screening, demonstration of characteristic translocations of EWSR1 (chromosome 22) or FUS (chromosome 16) by fluorescent in situ hybridization (FISH) can confirm the diagnosis. We are reporting three primary ES/pPNET of the CNS, two of which occurred in children. While the adult case demonstrates the classic histopathology, the two pediatric cases have histopathology that significantly deviates from the usual. One is suggestive of a primary sarcoma, and the other mimics an ependymoma, but all three cases are confirmed with FISH. These observations suggest that primary ES in the CNS may have histology different from the classic morphology and a high index of suspicion should be maintained in order to make the correct diagnosis. A search of the literature suggests that these tumors are most frequently seen in children and young adults. Imaging often shows a supratentorial enhancing mass that touches the leptomeninges. Survival over three years is good but long term prognosis is unknown [3, 4].

Signals that regulate the oncogenic fate of neural stem cells and progenitors

Brain tumors have frequently been associated with a neural stem cell (NSC) origin and contain stem-like tumor cells, so-called brain tumor stem cells (BTSCs) that share many features with normal NSCs. A stem cell state of BTSCs confers resistance to radiotherapy and treatment with alkylating agents. It is also a hallmark of aggressive brain tumors and is maintained by transcriptional networks that are also active in embryonic stem cells. Advances in reprogramming of somatic cells into induced pluripotent stem (iPS) cells have further identified genes that drive stemness. In this review, we will highlight the possible drivers of stemness in medulloblastoma and glioma, the most frequent types of primary malignant brain cancer in children and adults, respectively. Signals that drive expansion of developmentally defined neural precursor cells are also active in corresponding brain tumors. Transcriptomal subgroups of human medulloblastoma and glioma match features of NSCs but also more restricted progenitors. Lessons from genetically-engineered mouse (GEM) models show that temporally and regionally defined NSCs can give rise to distinct subgroups of medulloblastoma and glioma. We will further discuss how acquisition of stem cell features may drive brain tumorigenesis from a non-NSC origin. Genetic alterations, signaling pathways, and therapy-induced changes in the tumor microenvironment can drive reprogramming networks and induce stemness in brain tumors. Finally, we propose a model where dysregulation of microRNAs (miRNAs) that normally provide barriers against reprogramming plays an integral role in promoting stemness in brain tumors.

Embryonal tumor with abundant neuropil and true rosettes (ETANTR), ependymoblastoma, and medulloepithelioma share molecular similarity and comprise a single clinicopathological entity

Three histological variants are known within the family of embryonal rosette-forming neuroepithelial brain tumors. These include embryonal tumor with abundant neuropil and true rosettes (ETANTR), ependymoblastoma (EBL), and medulloepithelioma (MEPL). In this study, we performed a comprehensive clinical, pathological, and molecular analysis of 97 cases of these rare brain neoplasms, including genome-wide DNA methylation and copy number profiling of 41 tumors. We identified uniform molecular signatures in all tumors irrespective of histological patterns, indicating that ETANTR, EBL, and MEPL comprise a single biological entity. As such, future WHO classification schemes should consider lumping these variants into a single diagnostic category, such as embryonal tumor with multilayered rosettes (ETMR). We recommend combined LIN28A immunohistochemistry and FISH analysis of the 19q13.42 locus for molecular diagnosis of this tumor category. Recognition of this distinct pediatric brain tumor entity based on the fact that the three histological variants are molecularly and clinically uniform will help to distinguish ETMR from other embryonal CNS tumors and to better understand the biology of these highly aggressive and therapy-resistant pediatric CNS malignancies, possibly leading to alternate treatment strategies.

Supratentorial primitive neuroectodermal tumor presenting with intracranial hemorrhage in adult

A 24-year-old female patient presented with complaints of nausea, vomiting and of loss of consciousness lasted for 15 minutes with left sided weakness. Neuroradiological evaluation revealed a hemorrhagic mass lesion in the right frontal lobe. The patient was operated and intraoperative findings showed a cortical-subcortical hematoma including hemorrhagic and disrupted tissue with a pathologic purple tissue on the periphery of the hematoma. Postoperative course was uneventful and postoperative histopathological examination revealed primitive neuroectodermal tumor. The patient was then referred to medical and radiation oncology clinics for further evaluation and treatment.

Adults with CNS primitive neuroectodermal tumors/pineoblastomas: results of multimodal treatment according to the pediatric HIT 2000 protocol

Central nervous system primitive neuroectodermal tumors (CNS-PNET) and pineoblastomas (PBL) are rare in adulthood. Knowledge on clinical outcome and the efficacy and toxicities of chemotherapy in addition to radiotherapy is limited. Patients older than 21 years at diagnosis were followed in the observational arm of the prospective pediatric multicenter trial HIT 2000. After surgery, craniospinal irradiation and maintenance or sandwich chemotherapy were recommended. Radiotherapy was normo- (35.2 Gy; tumor region, 55.0 Gy; metastasis, 49.6 Gy) or hyperfractionated (40.0 Gy; tumor bed, 68.0 Gy; metastasis, 50-60 Gy). Maintenance chemotherapy consisted of eight courses (vincristine, lomustine, cisplatin). Sandwich chemotherapy included two cycles of postoperative chemotherapy followed by radiotherapy, and four courses of maintenance chemotherapy. Seventeen patients (CNS-PNET, n = 7; PBL, n = 10), median age 30 years, were included. Eight patients had a postoperative residual tumor and four patients metastatic disease. The median follow-up of ten surviving patients was 41 months. The estimated rates for 3-year progression-free survival (PFS) and overall survival were 68 ± 12 and 66 ± 13%, respectively. PBL compared to CNS-PNET tended towards a better PFS, although the difference was not clear (p = 0.101). Both chemotherapeutic (maintenance, n = 6; sandwich, n = 8) protocols did not differ in their PFS and were feasible with acceptable toxicities. Intensified regimens of combined chemo- and radiotherapy are generally feasible in adults with CNS-PNET/PBL. The impact of intensified chemotherapy on survival should be further assessed.

Intramedullary primitive neuroectodermal tumor presenting with rapidly-progressive cauda equina syndrome

A 39-year-old male presented with gait disturbances with rapid deterioration for 2 weeks. Neurological examination found paraparesis, sensory loss in the L1-S5 dermatomes, and vesicorectal dysfunction. Magnetic resonance (MR) imaging revealed a fusiform intramedullary tumor at T12-L1 levels with heterogeneous enhancement. The patient underwent microsurgical tumor resection. A myelotomy exposed a highly vascular tumor that was subtotally resected. Histological examination demonstrated hypercellular tumor accompanied by significant cell atypism and mitotic figures. Immunohistochemical staining was positive for glial fibrillary acidic protein, S-100 protein, synaptophysin, and INI-1, consistent with primitive neuroectodermal tumor (PNET). Postoperatively, the patient underwent irradiation to the whole craniospinal axis. He experienced local recurrence 7 months after surgery. MR imaging performed at 10 months revealed holocord progression and intracranial dissemination. The patient died 13 months after the onset of the disease. PNET should be considered in the differential diagnosis of an intramedullary spinal cord tumor.

A supratentorial primitive neuroectodermal tumor presenting with intracranial hemorrhage in a 42-year-old man: a case report and review of the literature

Introduction

We report on a very rare case of a supratentorial primitive neuroectodermal tumor in an adult, which presented with intracerebral hemorrhage, and review the relevant medical literature.

Case presentation

A 42-year-old Caucasian man complained of a sudden headache and nausea-vomiting. The patient rapidly deteriorated to coma. An emergency computed tomography scan showed an extensive intraparenchymal hemorrhage that caused significant mass effect and tonsilar herniation. During surgery, an increased intracranial pressure was recorded and extensive bilateral decompressive craniectomies were performed. A cherry-like intraparenchymal lesion was found in his right frontal lobe and resected. The patient died in the intensive care unit after approximately 48 hours. The resected lesion was identified as a central nervous system primitive neuroectodermal tumor.

Conclusion

Supratentorial primitive neuroectodermal tumors must be considered in the differential diagnosis of space-occupying lesions in adults. Spontaneous supratentorial hemorrhage due to primitive neuroectodermal tumors is an extremely rare but potentially lethal event.

H3.3 G34R mutations in pediatric primitive neuroectodermal tumors of central nervous system (CNS-PNET) and pediatric glioblastomas: possible diagnostic and therapeutic implications?

Pediatric glioblastomas recently have been exon sequenced with evidence that approximately 30 % of cases harbour mutations of the histone H3.3 gene. Although studies to determinate their role in risk stratification are on-going, it remains to be determined whether H3.3 mutations could be found in other tumors such as pediatric primitive neuroectodermal tumors of the central nervous system (CNS-PNETs) and whether the presence of H3.3 mutations in glioblastomas could be used as diagnostic tool in their differential diagnosis with CNS-PNETs. We performed a large mutational pyrosequencing-based screening on 123 pediatric glioblastomas and 33 CNS-PNET. The analysis revealed that 39/123 (31.7 %) glioblastomas carry H3.3 mutations. The K27M (AAG → ATG, lysine → methionine) mutation was found in 33 glioblastomas (26 %); the G34R (GGG → AGG, glycine → arginine) was observed in 6 glioblastomas (5.5 %). However, we also identified 4 of 33 cases (11 %) of CNS-PNETs harbouring a H3.3 G34R mutation. Multiplex ligation-dependent probe amplification analysis revealed PDGFR-alpha amplification and EGFR gain in two cases and N-Myc amplification in one case of H3.3 G34R mutated CNS-PNET. None of H3.3 mutated tumors presented a CDKN2A loss. In conclusion, because pediatric patients with glioblastoma and CNS-PNET are treated according to different therapeutic protocols, these findings may raise further concerns about the reliability of the histological diagnosis in the case of an undifferentiated brain tumor harbouring G34R H3.3 mutation. In this view, additional studies are needed to determine whether H3.3 G34 mutated CNS-PNET/glioblastomas may represent a defined tumor subtype.

Loss of INI1 protein expression defines a subgroup of aggressive central nervous system primitive neuroectodermal tumors

Pediatric embryonal brain tumors can be difficult to classify. Atypical teratoid rhabdoid tumors (ATRT) contain rhabdoid cells, while primitive neuroectodermal tumors (PNETs) are composed of "small round blue cells." Loss of INI1 is a common event in ATRT; therefore, we investigated if the loss of INI1 protein expression was also observed in central nervous system (CNS) PNET and pineoblastoma. A histological review of 42 CNS PNETs and six pineoblastomas was performed. INI1 expression was assessed by immunohistochemistry. Sequencing was performed on the mutational hotspots of INI1. INI1-immunonegative tumors were further investigated using fluorescence in situ hybridization. Epithelial membrane antigen (EMA) protein expression was assessed in six CNS PNETs to further define the phenotype. Five CNS PNETs without rhabdoid cell morphology were immuno-negative for both INI1 and EMA. Of these primary CNS PNET patients, three died <11 months postdiagnosis, which was dissimilar to the INI1-immunopositive primary CNS PNETs where 18/24 (75%) patients were alive 1 year postdiagnosis. We have identified a small subgroup of CNS PNETs which lack INI1 protein expression, but have no evidence of rhabdoid cell morphology. INI1 protein loss may occur through mechanisms other than gene deletion. INI1 immunohistochemistry should be performed for all CNS PNET cases.

Definition of genetic events directing the development of distinct types of brain tumors from postnatal neural stem/progenitor cells

Although brain tumors are classified and treated based upon their histology, the molecular factors involved in the development of various tumor types remain unknown. In this study, we show that the type and order of genetic events directs the development of gliomas, central nervous system primitive neuroectodermal tumors, and atypical teratoid/rhabdoid-like tumors from postnatal mouse neural stem/progenitor cells (NSC/NPC). We found that the overexpression of specific genes led to the development of these three different brain tumors from NSC/NPCs, and manipulation of the order of genetic events was able to convert one established tumor type into another. In addition, loss of the nuclear chromatin-remodeling factor SMARCB1 in rhabdoid tumors led to increased phosphorylation of eIF2α, a central cytoplasmic unfolded protein response (UPR) component, suggesting a role for the UPR in these tumors. Consistent with this, application of the proteasome inhibitor bortezomib led to an increase in apoptosis of human cells with reduced SMARCB1 levels. Taken together, our findings indicate that the order of genetic events determines the phenotypes of brain tumors derived from a common precursor cell pool, and suggest that the UPR may represent a therapeutic target in atypical teratoid/rhabdoid tumors.

Uterine neuroectodermal tumor with ependymoblastic features in an infant with clonal +del (2)(q11.2),-13: a possible role of increased gene dosage on 2pter-2q11.2 in the tumorigenesis

Clonal +(2)(q11.2),-13 was detected in a uterine neuroectodermal tumor with ependymoblastic features arising in an infant. The tumor expressed vimentin, nestin, CD56, CD99, microtubule-associated protein 1B (MAP 1B), focally microtubule-associated protein 2 (MAP 2), synaptophysin, neuron-specific enolase, and, very focally, epithelial membrane antigen. Because trisomy 2 was previously detected in a medulloepithelioma of pelvic soft tissue and in several neuroectodermal tumors of the central nervous system, this finding is indicative of a possible role of increased dosage of gene(s) on chromosome 2 in the tumorigenesis of these neoplasms and of their histogenetic relatedness.

INI1 immunohistochemical expression in glioblastoma: correlation with MGMT gene promoter methylation status and patient survival

AIMS

INI1 expression and its correlation with MGMT gene promoter methylation status and follow-up was investigated in 77 surgically removed glioblastomas then treated with radiotherapy (RT) or RT plus temozolomide (TMZ).

METHODS

INI1 was determined by immunohistochemistry and MGMT by methylation-specific PCR.

RESULTS

INI1 was expressed in 83.1% of cases. The median overall survival (OS) was 13.6 months in INI1+ tumours and 7.2 months in INI1- tumours. 31.3% of patients with INI1+ tumours were alive compared with 15.4% of patients with INI1- tumours. MGMT methylation was detected in 31.2% of cases. OS was significantly different between patients with methylated tumours and un-methylated tumours (p < 0.04), and between patients with RT+ TMZ and RT alone (p < 0.001). Considering both treatment and MGMT, the difference in OS was significant (p < 0.002). The difference in OS according to MGMT and INI1 was significant (p < 0.04). The longest median OS was recorded among methylated and INI1+ tumours. Among un-methylated tumours, the median OS was 11.1 months in INI1+ and 6.5 months in INI1- tumours. No patients were alive with un-methylated and INI1- tumours.

CONCLUSIONS

Loss of INI1 immunohistochemical expression in glioblastoma may be indicating an underlying molecular aberration accounting for the more aggressive clinical behaviour.

Primitive neuroectodermal tumors of the spine: a comprehensive review with illustrative clinical cases

Primary spinal primitive neuroectodermal tumors (PNETs) are uncommon malignancies that are increasingly reported in the literature. Spinal PNETs, like their cranial counterparts, are aggressive tumors and patients with these tumors typically have short survival times despite maximal surgery, chemotherapy, and radiation. Because no standard management guidelines exist for treating these tumors, a multitude of therapeutic strategies have been employed with varying success. In this study the authors perform a comprehensive review of the literature on primary spinal PNETs and provide 2 new cases that highlight the salient features of their clinical management.

Molecular diagnostics in embryonal brain tumors

Embryonal brain tumors are a heterogeneous group of neoplasms united by the presence of poorly differentiated stem-like cells. Molecular details are increasingly being used to separate them into biologically and clinically meaningful groups. For medulloblastoma, integrated mRNA expression profiling and DNA analysis by a number of research groups defines 4-6 distinctive molecular variants. A subset with prominent Wnt activity is associated with good clinical outcomes and classic histology. Medulloblastomas showing a Hedgehog gene expression signature are frequently of the desmoplastic/nodular subtype. Interestingly, Hedgehog activity is found in tumors arising either in infants or older teenagers and adults. The association of clinically aggressive medulloblastoma with MYC expression, large cell/anaplastic change and high levels of photoreceptor differentiation transcripts has also been noted in several studies. Immunohistochemical analysis of just one or two genes per molecular medulloblastoma variant may be sufficient for accurate classification, and this would be of great practical utility if validated. Advances have also been made in the classification of central nervous system (CNS) Primitive Neuroectodermal Tumors (PNET), as several groups have identified an amplicon at chromosome 19q13.41-42, which appears to define a unique PNET subtype associated with prominent true rosettes, young age and very poor outcomes.

Gone FISHing: clinical lessons learned in brain tumor molecular diagnostics over the last decade

Fluorescence in situ hybridization (FISH) is a powerful, morphology-based technique to assess targeted copy number alterations or gene rearrangements in formalin-fixed, paraffin-embedded tissues. It has a wide range of applications in routine clinical contexts to identify cytogenetic biomarkers for more accurate diagnosis and prognostic stratification. This review and update addresses practical uses of FISH as a molecular diagnostic tool in the setting of brain tumors, including gliomas, embryonal neoplasms, ependymomas and meningiomas, focusing on key genetic biomarkers, such as 1p19q codeletion, epidermal growth factor receptor (EGFR) gene amplification, BRAF rearrangement and many others. Also discussed are lessons learned over the past decade, including common technical issues to consider when implementing and interpreting FISH results in a clinical setting.