Spinal cord glioneuronal tumor with "rosetted" neuropil islands and meningeal dissemination: a case report

Malignant transformation of adult-onset pilocytic astrocytoma to diffuse leptomeningeal glioneuronal tumor within the thoracic spine: a case report and review of the literature

We describe a 31-year-old male who presented with progressive myelopathy from a thoracic pilocytic astrocytoma (PA). Following multiple recurrences and resections, 10 years after his index surgery, pathology revealed diffuse leptomeningeal glioneuronal tumor (DLGNT) with high-grade features. We discuss his clinical course, management, histopathological findings, and present a comprehensive review of spinal PA undergoing malignant transformation in adults and adult-onset spinal DLGNT. To our knowledge, we present the first reported case of adult-onset spinal PA malignant transformation to DLGNT. Our case adds to the paucity of clinical data characterizing such transformations and highlights the importance of developing novel management paradigms.

Glioneuronal tumor with neuropil-like islands in the spinal cord: A case report and literature review

RATIONALE

Glioneuronal tumor with neuropil-like islands (GTNI) is a distinctive neoplasm located in the cerebrum. Moreover, spinal GTNI is extremely rare. Herein, we present a case of spinal GTNI and review the related literature.

PATIENT CONCERNS

A 38-year-old Chinese woman presented to our hospital with a 6-month history of neck pain and a 1-month history of dizziness.

DIAGNOSES

Magnetic resonance imaging revealed a large intramedullary mass spanning the length of the spinal cord from C1 to C4. Microscopic and immunohistochemical examinations of the tumor tissue revealed findings typical of GTNI.

INTERVENTIONS

The patient underwent C1 to C4 intraspinal gross tumor resection.

OUTCOMES

Follow-up results showed that the patient had no recurrence 6 months after tumor resection.

LESSONS

GTNI in the spinal cord is a highly rare neoplasm with poor prognosis. Therefore, clinicians and pathologists should differentiate GTNI from other benign glioneuronal tumors, and long-term follow-up of patients with spinal GTNI is necessary.

Spinal cord glioneuronal tumor with rosetted neuropil-like islands in pediatric age group

Glioneuronal neoplasms are rare tumors. Recently, an unusual glioneuronal tumor histologically showing neuropil-like islands has been described. Here, we present such a tumor originating from spinal cord of a 14-year-old girl, who has scoliosis and urinary incontinence. Microscopically, the glial component was chiefly fibrillary astrocytic, punctuated by neuropil-like islands. Immunohistochemically, glial tissue was GFAP positive, and neuropil-like areas and big neurons were synaptophysin reactive. For astrocytic component Ki-67 proliferation index was 1% and p53 was immunonegative. This case is unique in that in the literature it is the second reported case in pediatric age group that is located at spinal cord.

An individual patient data meta-analysis on characteristics and outcome of patients with papillary glioneuronal tumor, rosette glioneuronal tumor with neuropil-like islands and rosette forming glioneuronal tumor of the fourth ventricle

Background and Purpose

In 2007, the WHO classification of brain tumors was extended by three new entities of glioneuronal tumors: papillary glioneuronal tumor (PGNT), rosette-forming glioneuronal tumor of the fourth ventricle (RGNT) and glioneuronal tumor with neuropil-like islands (GNTNI). Focusing on clinical characteristics and outcome, the authors performed a comprehensive individual patient data (IPD) meta-analysis of the cases reported in literature until December 2012.

Methods

PubMed, Embase and Web of Science were searched for peer-reviewed articles reporting on PGNT, RGNT, and GNTNI using predefined keywords.

Results

95 publications reported on 182 patients (PGNT, 71; GNTNI, 26; RGNT, 85). Median age at diagnosis was 23 years (range 4–75) for PGNT, 27 years (range 6–79) for RGNT, and 40 years (range 2–65) for GNTNI. Ninety-seven percent of PGNT and 69% of GNTNI were located in the supratentorial region, 23% of GNTNI were in the spinal cord, and 80% of RGNT were localized in the posterior fossa. Complete resection was reported in 52 PGNT (73%), 36 RGNT (42%), and 7 GNTNI (27%) patients. Eight PGNT, 3 RGNT, and 12 GNTNI patients were treated with chemo- and/or radiotherapy as the primary postoperative treatment. Follow-up data were available for 132 cases. After a median follow-up time of 1.5 years (range 0.2–25) across all patients, 1.5-year progression-free survival rates were 52±12% for GNTNI, 86±5% for PGNT, and 100% for RGNT. The 1.5-year overall-survival were 95±5%, 98±2%, and 100%, respectively.

Conclusions

The clinical understanding of the three new entities of glioneuronal tumors, PGNT, RGNT and GNTNI, is currently emerging. The present meta-analysis will hopefully contribute to a delineation of their diagnostic, therapeutic, and prognostic profiles. However, the available data do not provide a solid basis to define the optimum treatment approach. Hence, a central register should be established.

Disseminated glioneuronal tumor with neuropil-like islands of the spinal cord: a distinctive entity

BACKGROUND

Glioneuronal tumor with neuropil-like islands (GTNI) was recently added as a novel lesion in the most recent update of the World Health Organization classification of tumors of the central nervous system in 2007. Since this tumor's initial description, approximately 28 cases of GTNI have been published. In this report, we describe the ninth case of a spinal GTNI in the world literature.

METHODS

We report a case arising in a 2-year-old female patient who presented with headaches associated with intermittent vomiting due to a tetraventricular hydrocephalus.

RESULTS

After ventriculoperitoneal shunt placement, the patient presented with lower extremity motor weakness and sensory disturbance. A dorsolumbar spine magnetic resonance imaging scan revealed an intramedullary spinal neoplasm involving T12 through L2 in association with the thick linear enhancement of the spinal cord surfaces. A brain magnetic resonance imaging scan demonstrated focal leptomeningeal enhancement in the Sylvian fissures, the basal cistern, tentorium, and multiple small cystic-like lesions extending on the cerebellar surface, brainstem, and temporal lobes. The patient underwent a T11-L2 laminectomy for a gross total tumor resection. Histology revealed a World Health Organization grade II GTNI.

CONCLUSIONS

GTNI is a rare type of glioneuronal tumor that has recently been described in the literature. The outcome of this case seems to have an unfavorable clinical course despite their low-grade morphology. However, the combination of gross total resection and adjuvant chemo-radiotherapy can enhance chances for longer survival among children with spinal GTNI associated with meningeal dissemination, and a clinical follow-up of a large series will be necessary to evaluate the long-term prognosis.

Glioneuronal tumor with neuropil-like islands: clinical, morphologic, immunohistochemical, and molecular features of three pediatric cases

Glioneuronal tumors with neuropil-like islands are rare. The 1st reported cases were localized in the cerebral hemispheres of adults, showed homogeneous histopathologic features (infiltrating astrocytic growth and neuropil-like islands rimmed by neuronal cells), and had an unfavorable behavior. We report 3 pediatric cases (1 boy and 2 girls, ages 4, 6, and 8 years, respectively). The boy had a cerebral tumor, and the girls had a spinal tumor. The younger girl also had multiple posterior fossa lesions. The boy and older girl underwent a gross total resection. The younger girl underwent a subtotal resection of the spinal tumor; posterior fossa lesions were not surgically treated. The boy and younger girl are in complete remission at 33 and 24 months, respectively, after surgery and subsequent high-dose chemoradiotherapy. The older girl had a recurrence that was partially resected. Afterward, she started high-dose chemoradiotherapy and had an optimal radiologic response at 4 months follow up. Microscopically, the common denominator was the presence of synaptophysin-positive neuropil-like islands. One tumor showed ependymal features (pseudorosettes and punctate epithelial membrane antigen immunopositivity). Two tumors had 1p deletion. 19q deletion, MGMT gene promoter methylation, EGFR amplifications or polysomy, and EGFR, IDH1, IDH2, and TP53 genes mutation analyses yielded negative results. In conclusion, glioneuronal tumor with neuropil-like islands can affect children, arise in the spinal cord, and show ependymal features in its glial component. A high-dose chemoradiotherapy program is effective.

Spinal cord glioneuronal tumor with neuropil-like islands with 1p/19q deletion in an adult with low-grade cerebral oligodendroglioma

Glioneuronal tumor with neuropil-like islands (GTNI) is considered a rare variant of astrocytoma, characterized by discrete aggregates of cells expressing neuronal markers that punctuate a GFAP-positive glial background. Of the 24 published GTNI cases, only two occurred in adult spinal cords; none occurred concurrent with another CNS tumor; and none of those tested exhibited the 1p/19q deletion typical of oligodendroglioma. A 48-year-old man without significant past medical history was diagnosed with a WHO grade II oligodendroglioma by stereotactic biopsy of a lesion discovered after the patient suffered a generalized tonic-clonic seizure. By FISH analysis, this tumor exhibited the 1p/19q deletion present in up to 80% of oligodendrogliomas. The patient received 14 monthly cycles of temozolomide, and his cerebral tumor had a minor response. When the patient subsequently reported progressive paresthesias of his lower extremities, an MRI revealed an enhancing, cystic tumor of the thoracic spinal cord that was diagnosed as GTNI by histological analysis. By FISH analysis, this lesion exhibited the same 1p/19q deletion present in the concurrent cerebral oligodendroglioma. This case of a spinal cord GTNI with 1p/19q deletions constitutes the third report of a spinal cord GTNI in an adult patient; the first report of a GTNI in an individual with a separate CNS neoplasm; and the first report of a GTNI with 1p/19q deletions. This case establishes a potential genetic kinship between GTNI and oligodendroglioma that warrants further investigation.

Intraventricular glioneuronal tumor with disseminated lesions at diagnosis--a case report

A 55-year-old man presented with a large tumor in his lateral ventricles. Magnetic resonance imaging revealed disseminated lesions in the third and fourth ventricles at the time of diagnosis. The patient underwent a partial removal of the tumor in the lateral ventricles. Histologically, the surgical specimens showed glioneuronal differentiation with ganglion or ganglioid cells, Rosenthal fibers, oligodendroglia-like honeycomb appearances, a spongy pattern, perivascular pseudorosettes, and many hyalinized blood vessels. Papillary structure was not observed. The neuronal component showed a moderately high labeling index of Ki-67/MIB-1. We diagnosed this tumor as atypical intraventricular glioneuronal tumor. The disseminated lesions disappeared after chemoradiation therapy with temozolomide, and the residual tumors in the lateral ventricles remained stable for 3 years after the surgery. We discuss the pathological diagnosis, therapy and clinical course with review of the literatures.

Glioneuronal tumor with neuropil-like islands of the spinal cord with diffuse leptomeningeal neuraxis dissemination

A 54-year-old Caucasian female presented with a 1 year history of intermittent numbness of the left leg progressing to bilateral, lower extremity sensory loss that advanced to include impaired vibration and proprioception. The subsequent thoracic spine magnetic resonance imaging (MRI) scan revealed a heterogeneous, avidly enhancing, centrally situated spinal cord mass involving T7 through T10 in association with thick linear enhancement of the anterior and posterior cord surfaces extending both superiorly and inferiorly. Both the cervical and lumbar spine MRI demonstrated diffuse leptomeningeal disease as well. A brain MRI revealed focal leptomeningeal enhancement in the left and right sylvian fissures, the suprasellar cistern, and the posterior fossa; a pattern consistent with metastatic disease. The patient underwent a T6-T10 laminectomy for tumor biopsy and debulking. Histology revealed a WHO grade III glioneuronal tumor with rosetted neuropil-like islands. Synaptophysin and neurofilament (NF) positive staining was noted within the neural appearing component, whereas, glial fibrillary acidic protein (GFAP) immunopositivity was evident in the fibrillary astrocytoma component of the tumor. The Ki-67 labeling index was 7%. This tumor pattern, now included in the 2007 World Health Organization (WHO) classification of central nervous system tumours as a pattern variation of anaplastic astrocytoma (Kleihues et al. In: Louis et al. (eds) WHO classification of tumours of the central nervous system, 2007), was first described in a four-case series by Teo et al. in 1999. The majority of subsequently reported cases described them as primary tumors of the cerebrum. Herein, we report a unique example of a spinal glioneuronal tumor with neuropil-like islands with associated leptomeningeal dissemination involving the entire craniospinal axis.

Cytogenetic study of glioneuronal tumor with neuropil-like islands: a case report

Glioneuronal tumor with neuropil-like islands (GTNI) is a recently recognized glioneuronal neoplasm but it was classified as an astrocytic tumor by the World Health Organization (WHO) in 2007. We performed a cytogenetic study in a case of GTNI arising in a 55-year-old man and analyzed its genetic alteration. It presented as a heterogeneously enhancing, multi-lobulating solid mass on MRI. Histopathologically, the tumor showed the biphasic feature of the predominating micronodular neuropil-like islands and the diffusely infiltrating glial component. In addition, the prominent blood vessels with perivascular hyalinization were observed. On cytogenetic study, loss of 4q, 5q, 11p and gain of 6p, 7, 8, 11q, 12p, 15q were found. The remaining tumor after subtotal resection progressed 7 months later, despite combined chemo- and radiotherapy. From the results, it seems that GTNI does not share pathologic or genetic features with conventional astrocytoma, suggesting a unique entity with aggressive behavior.

The expanding family of glioneuronal tumors

Three new entities have been recently added to the group of glioneuronal tumors in the most recent update of the World Health Organization classification of tumors of the central nervous system: papillary glioneuronal tumor, rosetted glioneuronal tumor with neuropil-like islands, and rosette-forming glioneuronal tumor of the fourth ventricle. These tumors are relatively infrequent lesions, and because of that, they can be challenging to diagnose for the practicing pathologist. In this article, we summarize the clinical and pathologic findings of these new lesions.

Spinal glioneuronal tumor with neuropil-like islands and meningeal dissemination: histopathological and radiological study of a pediatric case

Cerebral and spinal location of glioneuronal tumors have been recently described as a novel type of primary CNS neoplasia. A distinctive rare form of glioneuronal tumors with neuropil-like islands (GTNI) have been reported to occur in the adult cerebrum, whereas spinal GTNI localization is extremely rare. In the present report we describe a case of a 15-month-old child with a spinal GTNI of the cervical region and meningeal dissemination. Histologically the tumor was composed of round, small neurocytic-like cells arranged around eosinophilic neuropil cores and embedded in a diffuse fibrillar glial component forming prominent "rosetted" neuropil islands displaying strong immunoreactivity for neuronal markers. Cerebral GTNI shows abundant glial components not rarely exhibiting anaplastic features that justify their inclusion within the group of diffuse astrocytomas. In contrast, including our case, spinal GTNI do not show histological evidence of anaplastic features and exhibits a significant neuronal component that may imply considering these lesions in a separate group. Nevertheless, due to their exceptional rarity, the natural history of these lesions is not yet fully understood, but spinal GTNI seems to have an unfavorable clinical course despite their benign histopathological features, which must be taken into account for appropriate treatment and follow-up of the patient.

The 'rosette-forming glioneuronal tumor' of the fourth ventricle

Tumors containing both neuronal and glial components are a rare heterogeneous group with unique features that require further subclassification. The rosette-forming glioneuronal tumor of the fourth ventricle is one of a number of recently described glioneuronal tumors, which has been accorded official WHO nosologic status only in 2007. We describe the clinical and pathologic features of two patients with rare rosette-forming glioneuronal tumors of the fourth ventricle, one of which was associated with dysgenetic tricho-rhinopharyngeal type I syndrome.

Surgical neuropathology update: a review of changes introduced by the WHO classification of tumours of the central nervous system, 4th edition

CONTEXT

The World Health Organization (WHO) recently published its 4th edition of the classification of tumors of the central nervous system, incorporating a substantial number of important changes to the previous version (WHO 2000). The new WHO classification introduces 7 changes in the grading of central nervous system neoplasms, ranging in significance from minor to major, in categories of anaplastic oligoastrocytomas, meningiomas, choroid plexus tumors, pineal parenchymal tumors, ganglioglioma, cerebellar liponeurocytoma, and hemangiopericytomas. The 4th edition also introduces 10 newly codified entities, variants, and patterns, as well as 1 new genetic syndrome. A number of established brain tumors are reorganized, including medulloblastomas and primitive neuroectodermal tumors, in an attempt to more closely align classification with current understanding of central nervous system neoplasia.

OBJECTIVE

To summarize and discuss the most significant updates in the 4th edition for the practicing surgical pathologist, including (1) changes in grading among established entities; (2) newly codified tumor entities, variants, patterns, and syndromes; and (3) changes in the classification of existing brain tumors.

DATA SOURCES

The primary source for this review is the WHO Classification of Tumours of the Central Nervous System, 4th edition. Other important sources include the 3rd edition of this book and the primary literature that supported changes in the 4th edition.

CONCLUSIONS

The new edition of the WHO blue book reflects advancements in the understanding of brain tumors in terms of classification, grading, and new entities. The changes introduced are substantial and will have an impact on the practice of general surgical pathologists and neuropathologists.

Rosette-forming glioneuronal tumor of the fourth ventricle: Report of two cases with a differential diagnostic overview

We report on clinicopathological findings in two cases of rosette-forming glioneuronal tumor of the fourth ventricle (RGNT) occurring in females aged 16 years (Case 1) and 30 years (Case 2). Symptoms included vertigo, nausea, cerebellar ataxia, as well as headaches, and had been present for 4-months and 1 week, respectively. Magnetic resonance imaging (MRI) indicated a cerebellar-based tumor of 1.8 cm (Case 1) and 5 cm (Case 2) diameter each, bulging into the fourth ventricle. Case 2 involved a cyst-mural-nodule configuration. In both instances, the solid component appeared isointense on T(1) sequences, hyperintense in the T(2) mode, and enhanced moderately. Gross total resection was achieved via suboccipital craniotomy. However, functional recovery was disappointing in Case 1. On microscopy, both tumors comprised an admixture of low-grade astrocytoma interspersed with circular aggregates of synaptophysin-expressing round cells harboring oligodendrocyte-like nuclei. The astrocytic moiety in Case 1 was nondescript, and overtly pilocytic in Case 2. The architecture of neuronal elements variously consisted of neurocytic rosettes, of pseudorosettes centered on a capillary core, as well as of concentric ribbons along irregular lumina. Gangliocytic maturation, especially "floating neurons", or a corresponding immunoreactivity for neurofilament protein was absent. Neither of these populations exhibited atypia, mitotic activity, or a significant labeling for MIB-1. Cerebellar parenchyma included in the surgical specimen did not reveal any preexisting malformative anomaly. Despite sharing some overlapping histologic traits with dysembryoplastic neuroepithelial tumor (DNT), the presentation of RGNT with respect to both patient age and location is consistent enough for this lesion to be singled out as an autonomous entity.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO ‘Blue Book’, the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

Glioneuronal Tumor With Neuropil-like Islands (GTNI): A Report of 8 Cases With Chromosome 1p/19q Deletion Analysis

Glioneuronal tumor with neuropil-like islands (GTNI) is a rare neoplasm harboring circumscribed loci of neuronal differentiation and diffusely infiltrating astroglial and oligodendrocytelike components. We report 8 previously unpublished examples of GTNI, specifically studied for chromosome 1p and 19q allelic losses. All tumors showed characteristic histologic features and immunoprofile. One primary tumor displayed frankly malignant histology with frequent mitoses, microvascular proliferation, and necrosis. This tumor progressed within months of the initial resection. Three other tumors (2 low-grade and 1 showing only focal microvascular proliferation) recurred at 2 years, 3 years, and 1 year, respectively. All cases were evaluated for 1p/19q allelic losses by standard polymerase chain reaction-based loss of heterozygosity assays. No evidence of 1p/19q losses was found in 7 of 8 tumors. One tumor demonstrated small interstitial deletions at 1p36 (at D1S1612 and D1S513, but not at D1S548 or D1S1592) and a small interstitial deletion at 19q13 (at D19S219 and D19S412, but not at PLA2G4C). The lack of large, whole-arm 1p/19q losses (such as those found in oligodendroglial tumors), aberrant p53 expression, and the predominance of astroglial components may indicate a biologic relationship of the GTNI to diffuse astrocytoma. Although GTNI shares some morphologic features with recently reported cases of oligodendroglioma with neurocytic differentiation, the 2 tumors appear different at the molecular genetic level.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

Mixed glioneuronal tumors: recently described entities

CONTEXT

Several distinctive mixed glioneuronal tumors that warrant recognition as clinicopathologic entities have been recently described by neuropathologists.

OBJECTIVE

To summarize important clinical, radiologic, and pathologic findings for 3 novel glioneuronal tumors (papillary glioneuronal tumor, rosetted glioneuronal tumor, and rosette-forming glioneuronal tumor of the fourth ventricle).

DATA SOURCES

Recent reports in the pathology literature and the authors' experience with mixed glioneuronal tumors at a major cancer center.

CONCLUSIONS

Histologic features enabling recognition of these recently described glioneuronal tumors are presented along with remarks concerning the classification of mixed neuronal and glial tumors exhibiting unconventional appearances.

Ependymomas with neuronal differentiation: a morphologic and immunohistochemical spectrum

The category of mixed glioneuronal tumors of the CNS is rapidly losing its definition as encompassing tumors composed of histologically distinct neuron variants and glia. We encountered five ependymomas with neuronal differentiation seen in two by histology, in two by immunohistochemistry alone, and in one by electron microscopy. Antibodies against GFAP, S-100 protein, neurofilament protein, chromogranin, synaptophysin, Neu-N, and EMA were applied. Ultrastructural studies were also performed. In addition, 33 randomly selected ependymomas of various histologic types were screened for these same antigens. Cases 1 and 2 were anaplastic and showed clearly defined neuropil islands or pale islands as in nodular desmoplastic medulloblastoma, respectively. The tumors affected a 16-year-old male and a 5-year-old female and involved the right frontoparietal lobe and fourth ventricle, respectively. The islands were positive for synaptophysin and Neu-N (cases 1 and 2), and chromogranin (case 1). Cases 3-5, as well as 7 of the 33 screened ependymomas, showed a suggestion of neuronal differentiation by immunohistochemistry alone, including immunoreactivity for Neu-N (n = 8), synaptophysin (n = 4), neurofilament protein (n = 4), and chromogranin (n = 2). Five tumors each were WHO grade II and III. Electron microscopy performed on the two cases with neuronal islands demonstrated microtubule bundles and dense core granules (case 1) and poorly differentiated cells with high nuclear/cytoplasmic ratios, with intermediate filament accumulation and rare cilia (case 2). Cases identified by immunohistochemistry or electron microscopy demonstrated dense core granules (n = 5) and aligned microtubules (n = 3). Neuronal differentiation occurs in ependymomas but is less frequently definitive (histologic, ultrastructural) than merely a limited immunohistochemical finding. The clinical significance of these observations is unknown but deserves further exploration.

Unusual malignant glioneuronal tumors of the cerebrum of adults: a clinicopathologic study of three cases

Malignant glioneuronal tumors of the brain are rare and poorly characterized. Herein, we report the clinicopathologic features of three examples with unusual morphologies including both glial and neuronal differentiation. Hematoxylin and eosin-stained slides were reviewed in all cases. Immunohistochemical stains were performed on formalin-fixed, paraffin-embedded sections. Transmission electron microscopy (EM) was performed on both formalin-fixed (n=1) and paraffin embedded tissue (n=2). The immunogold technique for localization of GFAP was also performed. Two patients were male and one was female, age 66, 84, and 34 years, respectively. Radiologic studies demonstrated hyperdensity on CT (n=3), multicentricity (n=2), and a cortical based solid component with a cystic extension into underlying white matter (n=2). At surgery, all three tumors were superficial and relatively circumscribed. Histologically, they were composed of large epithelioid cells (n=3), spindle cells (n=1), and poorly differentiated smaller cells with high nuclear/cytoplasmic ratios (n=1). Brisk mitotic activity and coagulative non-palisading necrosis were present in all cases. The tumors were immunopositive for GFAP (n=3), S-100 (n=3), synaptophysin (n=3), chromogranin (n=3), Neu-N (n=2), and neurofilament protein (n=2). Stains for EMA were negative. EM demonstrated convincing neurosecretory granules in one case, some in filament-containing cells immunogold labeled for GFAP. Two patients expired 3-5 weeks after surgery. True malignant neoplasms with glial and neuronal differentiation do occur in the central nervous system of adults and may pursue a highly aggressive course. The use of minimal diagnostic criteria, e.g., immunoreactivity for a single antigen like neurofilament protein, may not be sufficient and should be discouraged.

Neurocytoma: a comprehensive review

Central neurocytomas (CN) are uncommon tumors of the central nervous system, most descriptions of which available in the literature are in the form of isolated case reports and small series. Owing to this rare incidence, diagnosis and management of this neoplasm remain controversial. Usually, these tumors affect lateral ventricles of young adults and display characteristic neuroimaging and histomorphologic findings. Neurocytomas often mimic oligodendrogliomas when confirmation of diagnosis rests on immunohistochemistry, ultrastructure, and genetic studies. Extraventricular neurocytomas, situated entirely within the brain parenchyma and spinal cord, have also been reported. Typically, CN are associated with a favorable outcome although cases with more aggressive clinical course with recurrences are not unknown. MIB-1 labeling index (LI) of >2% often heralds poor prognosis and tumour recurrence. Safe maximal resection is presently considered the ideal therapeutic option, with best long-term prognosis in terms of local control and survival. The role of adjuvant radiotherapy apparently seems to benefit patients with incomplete resection and in atypical neurocytoma. Utility of other therapeutic regimen, however, remains shrouded in controversy. Epidemiology, histogenesis, clinical profile, histology, neuroimaging and therapeutic modalities of neurocytomas have been comprehensively reviewed, with special emphasis on CN and extraventricular neurocytomas and their atypical counterparts.

Novel low-grade glioneuronal neoplasm presenting in an octogenarian: Case report and review of the literature

Glioneuronal neoplasms are rare tumors that typically affect patients in the first three decades of life. Since the publication of the World Health Organization (WHO) 2000 classification of tumors, further variants of these tumors have been reported. We present an 83-year-old gentleman who presented with a history of ataxia and weight loss. MRI and CT scan revealed a ring-enhancing bihemispheric lesion in the premotor cortex consistent with a malignant primary brain tumor crossing the corpus collosum. The patient underwent a sterotactic biopsy with drainage of the cystic component. Histopathologic studies revealed a mixed glioneuronal tumor with benign characteristics. A craniotomy was performed and the tumor was resected. Postoperatively, the patient has been followed with serial MRI scans with no evidence of disease recurrence at 27 months. Glioneuronal tumors are extremely uncommon in the octogenarian population, however, it is important to include them in the differential diagnosis of intracerebral masses. They are histopathologically quite heterogeneous, and in this report we present a novel subtype. Radiographically, these lesions can mimic more aggressive primary brain tumors.

Mixed glioneuronal tumour of the fourth ventricle with prominent rosette formation

We describe three unusual tumours characterized by a mixture of glial and neuronal differentiation, involvement of the posterior fossa and formation of rosettes. Mixed glial-neuronal tumours of the posterior fossa are rare and poorly described neoplasms. However, several distinctive entities have appeared in the literature over recent years under a variety of different names. Our cases demonstrate the morphological features of the 'rosette-forming glioneuronal tumour of the fourth ventricle', a recently identified tumour characterised by its unique location, neurocytic pseudo-rosette formation and the presence of a low grade astrocytoma component. The long term prognosis of these tumours remains unclear. However, the clinical data available including the cases presented here, along with the histological features, suggest that these are low grade tumours with a good prognosis after surgical resection.

Primary neurocytoma of the spinal cord: a case report and review of literature

Most central neurocytomas (CN) and spinal neurocytomas (SN) have a bland well-differentiated histologic picture and uneventful clinical course. However, rare examples showing histologic atypia, recurrence and even CSF dissemination have been reported. Herein we report a case of recurrent spinal neurocytoma in a 24-year-old male who presented with a 2-month history of weakness and numbness of the left upper and lower limbs, and was previously operated at the same site 10 months ago. MRI revealed a contrast enhancing intramedullary mass involving C5-T1 region. Radiologic and operative impression at both surgeries was that of a glioma, possibly anaplastic. Histologic and immunohistochemical features in both resections were those of an atypical neurocytoma. The tumor showed rare mitoses, focal mild vascular proliferation in both specimens, and necrosis in the initial specimen. MIB1 labeling indices were 9 and 10%, respectively. Based on the analysis of this case and limited data from the literature, it is hypothesized that SN shows a histopathologic picture, immunoprofile and biologic behavior very similar to CN. However, the presence of histologic atypia and increased MIB1 index in SN appear to more closely correlate with tumor recurrence and a worse overall outcome, in part due to their location in the critical region of cervical spinal cord. Therefore, we hypothesize that SN with atypia requires a close clinical follow up. As in CN, radiation therapy is perhaps best reserved for atypical, progressive and recurrent SN.

Ependymoma with neuropil-like islands: a case report with diagnostic and histogenetic implications

We describe a case of ependymoma with neuronal differentiation in form of neuropil-like islands. A 6-year-old boy presented at clinical examination for a short history of headaches and vomiting. Brain computed tomography showed a large, partially cystic, parieto-occipital lesion. The tumor was composed by glial fibrillary acidic protein-positive round cells with a perivascular arrangement and scattered neuropil-like islands, showing intense positivity for synaptophysin. Despite radiotherapy, the tumor recurred, showing frank features of anaplasia, but lacking the neuropil-like islands. The histological features of the tumor are discussed in the light of the concept that neuronal differentiation can occur occasionally in gliomas of different lineage without affecting the expected biological behavior.

Emerging Tumor Entities and Variants of CNS Neoplasms

Since the appearance in 2000 of the World Health Organization (WHO) classification for central nervous system (CNS) neoplasms, numerous descriptions of new entities or variants have appeared in the literature. In the group of neuronal and mixed glioneuronal neoplasms are lesions with distinctive morphological features that are still not included in a precise classification, including extraventricular neurocytoma, papillary glioneuronal tumor, rosette-forming glioneuronal of the fourth ventricle, glioneuronal with neuropil-like rosette, and DNT-like tumor of the septum pellucidum. The glioneuronal tumor with neuropil-like rosette and oligodendroglioma with neurocytic differentiation represent morphological variants of genetically proven diffuse gliomas. The lipoastrocytoma and the pilomixoid astrocytoma enlarge the group of astrocytic lesions. Rare, low-grade gliomas of the spinal cord with extensive leptomeningeal dissemination associated with unusual neuroimaging are described. The chordoid glioma of the third ventricle and the papillary tumor of the pineal region seem to be correlated by a common histogenesis from the specialized ependyma of the subcommissural organ. An embryonal tumor with neuropil and true rosettes combining features of neuroblastoma and ependymoblastoma is discussed. These new, recently described lesions indicate that the complex morphologic spectrum of CNS tumors is far from being completely delineated.

Low-grade gliomas and leptomeningeal dissemination: a poorly understood phenomenon

DISCUSSION

The leptomeningeal dissemination (LMD) of low-grade gliomas (LGGs) is reported in clinical neuro-oncology practice more and more frequently. It is estimated that 5% of all childhood LGGs present LMD at diagnosis and 7-10% at the time of progression. LMD has been reported in association with almost all the known subtypes of LGGs. Furthermore, "unusual " LGGs can be encountered among slow-growing brain neoplasm capable of LMD, which cannot comfortably be included in the present WHO brain tumour classification. The biological, genetic and clinical characteristics that seem to favour LMD are far from being understood. Similarly, the clinical profile of those children with disseminated LGGs has not yet been firmly established. Young, non-neurofibromatosis type 1 boys with large hypothalamic-chiasmatic pilocytic astrocytomas seem to be at increased risk of LMD. The neuroradiological appearance of LMD in childhood LGGs is similar to that observed in malignant tumours, except for those cases characterised by multiple superficial non-enhancing cystic lesions, which seem to be almost exclusively associated with a type of slow-growing not yet fully identified brain stem or spinal tumour. No firm guidelines for the treatment of these diseases are yet available, mostly due to the rarity of this condition and the existing uncertainties regarding their natural clinical history.

CONCLUSION

The evidence of LMD in children with LGGs does not seem to have a negative impact on patients' long-term outcome.

Oligodendrogliomas with neurocytic differentiation. A report of 4 cases with diagnostic and histogenetic implications

Oligodendroglioma represents a distinct type of diffuse glioma with a relatively favorable prognosis. Although an O2A-like glial progenitor cell of origin has been suggested, a neuronal-oligodendroglial progenitor cell is also of interest, particularly because variable degrees of neuronal marker expression have been reported in typical oligodendrogliomas. We present 2 female and 2 male patients (ages 34-54) with frontal lobe oligodendrogliomas containing a) morphologically distinct collections of small round cells with hyperchromatic nuclei, b) well-formed Homer Wright-like and perivascular rosettes, and c) demonstrable neuronal differentiation by immunohistochemistry and/or electron microscopy in the rosette-associated regions. Unlike extraventricular neurocytomas, these cases featured an infiltrative growth pattern and a classic oligodendroglioma immunophenotype in non-rosette bearing portions of each tumor. FISH analysis demonstrated chromosome 1p and 19q codeletions in 3 (75%) cases, both in regions with and without rosettes. Recurrences were common, although all patients are currently alive 4 months to 13 yr from initial diagnosis. Based on clinicopathologic and genetic features, we diagnosed these tumors as oligodendrogliomas with neurocytic differentiation. However, it is unclear whether they represent a) gliomas with divergent neuronal differentiation, b) a distinctive form of glioneuronal neoplasm, or c) a reflection of glioneuronal histogenesis in oligodendrogliomas in general. In any case, their occurrence suggests a histogenetic overlap between oligodendroglioma and extraventricular neurocytoma not previously recognized.