Papillary glioneuronal tumor: a new variant of mixed neuronal-glial neoplasm

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.

Childhood brain tumours due to germline bi-allelic mismatch repair gene mutations

Childhood brain tumours may be due to germline bi-allelic mismatch repair (MMR) gene mutations in MLH1, MSH2, MSH6 or PMS2. These mutations can also lead to colorectal neoplasia and haematological malignancies. Here, we review this syndrome and present siblings with early-onset rectal adenoma and papillary glioneural brain tumour, respectively, due to novel germline bi-allelic PMS2 mutations. Identification of MMR protein defects can lead to early diagnosis of this condition. In addition, assays for these defects may help to classify brain tumours for research protocols aimed at targeted therapies.

Papillary glioneuronal tumor present in a patient with encephalocraniocutaneous lipomatosis: case report

BACKGROUND AND IMPORTANCE

Encephalocraniocutaneous lipomatosis (ECCL) is a rare neurocutaneous syndrome presumably derived from a mesenchymal defect. No cases of ECCL associated with a neuroepithelial brain tumor have been described. Papillary glioneuronal tumor (PGNT) is also a rare brain tumor of mixed neuronal and glial cells. We believe this is the first case of ECCL combined with a PGNT to be described. The presence of the PGNT may reflect the maldevelopment of neuroepithelium in this ECCL patient and suggests a novel explanation of the pathogenesis of ECCL.

CLINICAL PRESENTATION

A 7-year-old girl with congenital lesions in the brain, spinal cord, eye, and skin was diagnosed with ECCL. Brain magnetic resonance images taken at 6 months of age showed no brain tumor other than stigmata of ECCL. Brain magnetic resonance image at the time of presentation at 7 years revealed a mass in the third ventricle. The tumor was completely removed, and pathological examination confirmed the diagnosis of PGNT. The tumor showed a divergent differentiation pattern both in the tissue histology and in primary cultures.

CONCLUSION

The occurrence of PGNT, a tumor resulting from the maldevelopment of neuroepithelium, broadens the spectrum of ECCL to include some defects in the neuroepithelium.

Seizures in patients with low-grade gliomas--incidence, pathogenesis, surgical management, and pharmacotherapy

Seizures complicate the clinical course of > 80% of patients with low-grade gliomas. Patients with some tumor variants almost always have epilepsy. Diffuse low-grade gliomas (LGG) are believed to cause epilepsy through partial deafferentiation of nearby brain cortex (denervation hypersensitivity). Glioneural tumors may interfere with local neurotransmitter levels and are sometimes associated with structural abnormalities of the brain which may produce seizures. The severity of tumor associated epilepsy varies considerably between patients. Some cases may present with a first seizure. Others suffer from long-standing pharmacoresistant epilepsy. Seizure control rates of > 70-80% can be expected after complete tumor resections. Patients with drug-resistant epilepsy require a comprehensive preoperative epileptological work-up which may include the placement of subdural (and intraparenchymal) electrodes or intraoperative electrocorticography (ECoG) for the delineation of extratumoral seizure foci. Partial and subtotal tumor resections are helpful in selected cases, i.e. for gliomas involving the insula. In one series, 40% of patients presented for surgery with uncontrolled seizures, i.e. medical therapy alone often fails to control tumor-related epilepsy. Use of the newer (second generation) non-enzyme inducing antiepileptic drugs (non-EIAED) is encouraged since they seem to have lesser interactions with other medications (e.g. chemotherapy). Chemotherapy and irradiation may have some minor beneficial effects on the patients' seizure disorder. Overall 60-70% of patients may experience recurrent epilepsy during long-term follow-up. Recurrent seizures (not infrequently heralding tumor recurrence) after surgery continue to pose significant clinical problems.

Classification and controversies in pathology of ependymomas

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Update on diagnostic practice: tumors of the nervous system

CONTEXT

Changes in the practice of diagnosing brain tumors are formally reflected in the evolution of the World Health Organization classification. Beyond this classification, the practice of diagnostic pathology is also changing with the availability of new tests and the introduction of new treatment options.

OBJECTIVE

Glioblastomas, oligodendrogliomas, glioneuronal tumors, and primitive pediatric tumors are discussed in an exemplary way to illustrate these changes.

DATA SOURCES

Review of relevant publications through Medline database searches.

CONCLUSIONS

The example of glioblastomas shows how new predictive markers may help identify subgroups of tumors that respond to certain therapy regimens. The development of new treatment strategies also leads to different questions in the assessment of brain tumors, as seen in the example of pseudoprogression or the changes in tumor growth pattern in patients taking bevacizumab. Oligodendrogliomas illustrate how the identification of 1p/19q loss as a cytogenetic aberration aids our understanding of these tumors and changes diagnostic practice but also introduces new challenges in classification. Glioneuronal tumors are an evolving group of lesions. Besides a growing list of usually low-grade entities with well-defined morphologic features, these also include more poorly defined cases in which a component of infiltrating glioma is often associated with focal neuronal elements. The latter is biologically interesting but of uncertain clinical significance. Oligodendrogliomas and glioneuronal tumors both illustrate the importance of effective communication between the pathologist and the treating oncologist in the discussion of these patients. Finally, the discussion of primitive pediatric tumors stresses the clinical importance of the distinction between different entities, like atypical teratoid rhabdoid tumor, "central" (supratentorial) primitive neuroectodermal tumor, "peripheral" primitive neuroectodermal tumor, and medulloblastoma. In medulloblastomas, the recognition of different variants is emerging as a prognostic factor that may in the future also predict therapy responsiveness.

Ultrastructural Heterogeneity of Gangliogliomas

Gangliogliomas are rare brain tumors, composed of neuronal and glial cells mixed in a different proportion. The basic histopathological pattern of gangliogliomas is well recognized but the variable microscopic appearance still can pose a challenge to the neuropathologist. The authors reanalyzed their series of gangliogliomas in the files of two departments of neuropathology. All analyzed tumors fulfilled the WHO histological criteria of ganglioglioma. Seven tumors were examined by electron microscopy. The following ultrastructural features were graded: presence of dense-cored vesicles, synaptic vesicles, synapses and intermediate filaments, abundant basal membranes, dystrophic neurites, autophagic vacuoles, and multivesicular bodies. Most of the neoplastic neurons were large, polyglonal or oval with well-developed subcellular organelles, round nuclei, and prominent nucleoli. In most cases there were abundant dense core vesicles, observed in both the tumor cell bodies as well as in their processes. Synapses were typically observed. Intermediate filaments were abundant in all tumors. The most intriguing ultrastructural finding was abundant presence of autophagic vacuoles. In 4 cases, multivesicular bodies were observed. All of the tumors with multivesicular bodies also contained abundant autophagic vacuoles.

Two cases of papillary glioneuronal tumours

We report two cases of papillary glioneuronal tumour. Both patients underwent gross total resection of their tumour. One of them was also treated by radiotherapy. Neither tumour had recurred, 19 and 2 years after treatment, thus confirming the good prognosis commonly associated with this tumour.

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.

Aggressive variant of a papillary glioneuronal tumor. Report of 2 cases

Papillary glioneuronal tumors are a newly recognized type of brain neoplasm characterized by prominent pseudopapillary structures and glioneuronal elements. All prior cases have shown that these tumors have an indolent course. The authors present 2 patients with an aggressive variant of the tumor. The first patient had dissemination of her tumor and the second had local spreading. Therefore, the authors conclude that papillary glioneuronal tumors do not always behave in a strictly benign fashion.

Chromosome 1p and 19q deletions in malignant glioneuronal tumors with oligodendroglioma-like component

Malignant glioneuronal tumors (MGNT) are suggested to be a new entity of glioma defined morphologically as any malignant glioma showing immunohistoichemical evidence of neuronal differentiation. We encountered seven cases of MGNT with oligodendroglioma-like component and investigated alternations of chromosome 1p and 19q in these tumors. Seven patients ranged from 33 to 62 years of age, four females and three males. Immunohistochemical study of these tumors was performed using neuronal markers (synaptophysin, neurofilament, beta-tubulin, chromogranin A and NeuN), astrocytic marker (GFAP) and Ki-67. We undertook a molecular cytogenetic study of tumor specimens obtained from seven patients using fluorescence in situ hybridization (FISH) with DNA probes mapping to chromosome 1p36, 1q25, 19p13 and 19q13. Histologically, these tumors resembled anaplastic oligodendroglioma. Immunohistochemically, tumor cells were immunoreactive for synaptophysin (7/7), neurofilament (6/7), beta-tubulin (5/7), chromogranin A (4/7), NeuN (2/7) and GFAP (7/7). The Ki-67 labeling index ranged from 4.5% to 20.7%. FISH analysis demonstrated either 1p or 19q deletion in all seven cases (100%) and both 1p and 19q deletions in five cases (71%). The 1p deletion was detected in six of seven cases (86%) and 19q deletion was also detected in six (86%). 1p and 19q deletions were present in MGNT, especially those with oligodendroglial components. We suggest that the oligodendroglial-like feature was associated with not only 1p or 19q loss but also differentiation along neuronal cell lines as a factor of favorable prognosis in glial tumors. It is inappropriate to make a diagnosis of oligodendroglioma based only on morphological resemblance to oligodendroglia.

Hypothalamic papillary tumor in a patient with tuberous sclerosis

We here report an unusual tumor of the suprasellar region featuring a papillary growth pattern and cytokeratin expression in a 10-year-old boy with tuberous sclerosis. This hitherto undescribed low-grade hypothalamic tumor extends the spectrum of tumors associated with the tuberous sclerosis complex.

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.

CLINICAL IMPLICATIONS OF THE INFRATENTORIAL ROSETTE-FORMING GLIONEURONAL TUMOR

OBJECTIVE

This article describes our experience with two patients who presented with unusual tumors in the cerebellar vermis and cerebral aqueduct. Although sparing the fourth ventricle proper, both tumors had histological features consistent with the rare diagnosis of a rosette-forming glioneuronal tumor of the fourth ventricle, of which only 19 cases have been reported previously. A review of the clinical features and courses of all 21 cases is presented and management recommendations are given.

CLINICAL PRESENTATION

Patient 1 was a 42-year-old man who presented with a headache of 1 day's duration and no neurological signs, in whom magnetic resonance imaging disclosed a nonenhancing mass lesion occupying the proximal cerebral aqueduct. Patient 2 was a 38-year-old woman with a long history of intermittent giddiness, no neurological signs, and a magnetic resonance imaging scan that demonstrated a nonenhancing and subtle abnormality in the cerebellar vermis.

INTERVENTION

Biopsy was performed on both lesions, the first endoscopically and the second via craniotomy. The only postoperative complication was short-lived double vision and poor upgaze in Patient 1.

CONCLUSION

These cases demonstrate that the rosette-forming glioneuronal tumor may be more accurately categorized as an infratentorial tumor rather than a tumor of the fourth ventricle. Because the literature indicates that this is a tumor with little potential for malignant behavior and considerable morbidity can accompany attempts at resection, a conservative management approach would seem well advised. If this tumor is to be managed conservatively, because of the paucity of extended follow-up data, long-term radiological and clinical surveillance is strongly recommended.

The 2007 WHO classification of tumors of the nervous system: controversies in surgical neuropathology

Controversy surrounds the recent 2007 WHO Classification of Tumours of the Nervous System. A number of nosologic issues remain to be resolved, some a reflection of conceptual disagreement, others the result of inadequate data to permit their definitive resolution. Among these and discussed herein are (i) the nosologic place of highly anaplastic oligoastrocytic tumors, (ii) the forms and significance of microvascular changes in high-grade gliomas, (iii) the makeup of the glioneuronal tumors category, (iv) the subclassification of pineal parenchymal tumors of intermediate type, and (v) the classification of principle forms of mesenchymal neoplasms, specifically hemangiopericytoma and solitary fibrous tumor. These issues and others are the substance of this and an upcoming companion article.

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.

Lipomatous supratentorial primitive neuroectodermal tumor with glioblastomatous differentiation

Cases of cerebral neuroblastoma or supratentorial primitive neuroectodermal tumor with malignant gliomatous components are relatively uncommon. Less frequent is the combination of these 2 elements with a mesenchymal component. This is a case report of a lipomatous supratentorial primitive neuroectodermal tumor with glioblastomatous differentiation occurring in a 48-year-old woman. She presented with headaches and confusion. A right parietal lobe mass was excised and subsequently recurred, requiring additional surgery 10 months later. The patient died 13 months after initial surgery. Histologic findings showed a proliferation of small rounded synaptophysin-positive neural cells consistent with neuroblastoma. These cells were arranged against a benign lipomatous background. The second resection consisted primarily of glioblastomatous-like tissue with intermixed lipomatous component. The glioblastoma component was marked by prominent cellularity, moderate nuclear pleomorphism, readily identifiable mitotic activity, vascular proliferative changes, and necrosis. The glioblastomatous component of the tumor demonstrated glial fibrillary acidic protein immunoreactivity. A Ki-67 labeling index of 18.9% was noted in the initial resection. The literature on similar-appearing lesions is reviewed.

The 2007 WHO Classification of Nervous System Tumors: newly recognized members of the mixed glioneuronal group

The clinical and pathologic features of two glioneuronal neoplasms newly incorporated in the 2007 revision of the WHO classification of nervous system tumors are reviewed. These are the papillary glioneuronal tumor and the rosette-forming glioneuronal tumor of the fourth ventricle.

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.

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.

Papillary glioneuronal tumour: a report of a rare case and review of literature

INTRODUCTION

Amongst the mixed glioneuronal tumours, 'papillary glioneuronal tumour', a new variant, has been described recently.

CASE REPORT

We report a case of papillary glioneuronal tumour in a 4-year-old boy who presented with fever, weakness of left upper and lower limbs and headache for the last 2.5 month. Radiologic examination showed a cystic space-occupying lesion with mural nodule in the right frontal lobe with extension into white matter. Surgical excision of a large cystic mass with small solid nodule was done. Pathological examination revealed a well-circumscribed tumour showing predominantly papillary architecture with focal aggregates of cells in sheets. The papillae were composed of hyalinised blood vessels lined by single to multi-layered cells. The tumour cells showed mild pleomorphism without any necrosis. The individual tumour cells had scant eosinophilic cytoplasm, round to oval hyperchromatic nucleus with occasional mitoses. The tumour cells were immunopositive for glial fibrillary acidic protein, synaptophysin, vimentin, and S-100 protein, but negative for neurofilament, epithelial membrane antigen, cytokeratin and CD34. MIB-1 labelling index was approximately 12% in the highest proliferating areas. In view of subtotal excision of the tumour and high MIB-1 labelling index (LI), the patient was given chemotherapy and he is doing well at 1-year follow-up.

DISCUSSION

This report supports the existence of this rare tumour. Some of its rare clinicopathological features like young age, cyst with mural nodule, presence of mitoses and raised MIB-1 LI need to be documented.

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.

Papillary glioneuronal tumor: a new entity awaiting inclusion in WHO classification

Papillary glioneuronal tumor (PGNT) is a recently described lesion of the brain, which is still not included as a separate entity in WHO classification. To date 32 cases of PGNT have been reported in the world literature. We report the 33^rd case, a 41-year-old male who presented with pain in the nape of the neck. MRI showed a large, predominantly solid mass involving the cerebral parenchyma of the left temporal and parieto-occipital lobes with extension across the midline. Histologically, it was a mixture of glial and neuronal components. Architecturally, the tumor was notable for its pseudopapillary pattern with hyalinized vessels. PGNT is considered as a low grade neoplasm and surgical excision has been curative in most of the cases. More cases of PGNT need to be reported as they may add further knowledge about its biologic behavior and allow its recognition and classification.

Atypical papillary glioneuronal tumor

We describe a 34-year-old man who presented with headaches for about 3 months. Magnetic Resonance Imaging (MRI) revealed a large cystic tumor, involving the right frontoparietal lobe region. Pathological study revealed a papillary glioneuronal tumor (PGNT) with mitotic activity and a Ki-67 labeling index of approximately 15%. Five years after radical surgery and radiotherapy, the patient is symptom-free, without tumor recurrence or residual tumor. This case supports the existence of an atypical variant of PGNT, with mitotic activity and high proliferative index, and suggests that in these tumors, histological findings of malignity not necessarily indicate a short-term unfavorable behavior.

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.

Superficial siderosis due to papillary glioneuronal tumor

Superficial siderosis of the central nervous system is a rare, progressive, irreversible and debilitating neurological disease characterized by the deposition of haemosiderin in the leptomeninges and the subpial layers of the brain and spinal cord. The main clinical findings are progressive bilateral sensorineural hearing loss, cerebellar ataxia and pyramidal tract signs. The present report describes a 49-year-old woman who presented with intermittent headache of 5 years duration. The pain had become more severe in the previous 6 months. Neurological examination revealed nothing abnormal. Computed tomography showed a cystic mass with apparent internal haemorrhage in the right frontal lobe and T(2)-weighted magnetic resonance imaging showed material of low signal intensity coating the entire surface of the brain. The mass was completely excised via craniotomy. A histopathological study identified the mass as a papillary glioneuronal tumour. The patient recovered well and is still neurologically normal 1 year later. This is the first documented case of superficial siderosis caused by this type of tumour.