Papillary glioneuronal tumour: clinicopathological and biochemical study of one case with 7-year follow up

Surgical Resection and Cellular Proliferation Index Predict Prognosis for Patients with Papillary Glioneuronal Tumor: Systematic Review and Pooled Analysis

BACKGROUND

Although the World Health Organization classifies papillary glioneuronal tumor (PGNT) as a grade I tumor, several malignant cases have been reported. In this study, we examined the clinical and prognostic characteristics of PGNT.

METHODS

PubMed, Embase, and institutional databases were queried for patient-level reports of PGNT, resulting in identification of 138 cases. Descriptive and Kaplan-Meier survival analyses were conducted. The threshold of significance was 0.05.

RESULTS

The mean age at presentation was 26.9 ± 16.3 years, and the incidence was higher in males (1.42:1). Tumors with a high Ki-67 index (≥5) were more likely to exhibit perilesional edema and ring enhancement on magnetic resonance imaging, trending toward significance (P = 0.114 and 0.113, respectively). Compared with tumors with a low Ki-67 index (<5), those with a high Ki-67 index were more likely to be treated with subtotal resection (STR) than with gross total resection (GTR) (Kruskal-Wallis test, P = 0.006) and with radiation therapy (χ2 test, P = 0.010). At 5 years post-treatment, PGNT had a mean progression-free survival (PFS) of 85.9 ± 3.9%. Males had a better 5-year PFS than females (94.0 ± 3.4% vs. 74.8 ± 7.8%; Mantel-Cox test, P = 0.002). Two-year PFS was higher after GTR than after STR (91.9 ± 3.6% vs. 46.7 ± 21.4%; Mantel-Cox test, P < 0.001). A low Ki-67 index was associated with a higher 5-year PFS compared with a high Ki-67 index (94.8 ± 3.6% vs. 55.6 ± 12.9%; Mantel-Cox test, P < 0.001).

CONCLUSIONS

PGNT is a benign tumor of young adults, but can present atypically as high grade. Male sex, low cellular proliferation, and maximal surgical resection are positive prognostic indicators for PGNT.

Papillary glioneuronal tumors: A radiopathologic correlation

OBJECTIVE

Papillary glioneuronal tumors (PGNT) are a rare and recently recognized tumor entity. The neuroimaging findings were reviewed to determine if any specific findings emerge to assist a preoperative diagnosis of PGNT.

MATERIALS AND METHODS

Seven histologically confirmed cases of PGNT were evaluated from 2004 to 2014. Clinical, neuroimaging and histological findings were reviewed and tabulated.

RESULTS

Headache and seizures were observed in 4 patients (57.1%) each. The majority (n=5, 71.4%) of lesions were periventricular and located in temporal lobe with 57.1% cases being solid cystic (n=4), and 42.9% being purely solid (n=3). Calcification and hemorrhage were noted in 3 cases (42.9%) and 5 cases (71.4%) respectively. The most frequent imaging feature was the presence of septations in the cystic component that enhanced on contrast which correlated with long pseudopapillary projections into the cyst cavity on histopathology. The solid inner component demonstrated heterogeneous enhancement. One case with tumor recurrence demonstrated hemorrhage with superficial siderosis, patchy diffusion restriction, raised choline and focal areas of raised perfusion which correlated on histopathology with increased cellularity and anaplasia.

CONCLUSION

Presence of cystic mass in periventricular location with septations and a solid inner component should raise a suspicion of PGNT on neuroimaging.

Papillary glioneuronal tumors: histological and molecular characteristics and diagnostic value of SLC44A1-PRKCA fusion

INTRODUCTION

Papillary Glioneuronal Tumor (PGNT) is a grade I tumor which was classified as a separate entity in the World Health Organization Classification of the Central Nervous System 2007 in the group of mixed glioneuronal tumors. This tumor is rare and subclassifying PGNT represents a challenge. Recently, a fusion between SLC44A1 and PRKCA which encodes a protein kinase C involved in MAPK signaling pathway has been described in two studies (five cases). The current study aimed at raising the cytogenetic, histological and molecular profiles of PGNT and to determine if SLC44A1-PRKCA fusion represented a specific diagnostic marker to distinguish it from other glioneuronal tumors.

RESULTS

We report on four pediatric cases of PGNT, along with clinico-radiologic and immunohistological features for which SLC44A1-PRKCA fusion assessment by fluorescence in situ hybridization, BRAF V600E and FGFR1 mutation by immunohistochemistry and direct DNA sequencing and KIAA1549-BRAF fusion by RT-PCR were performed. MAPK signaling pathway activation was investigated using phospho-ERK immunohistochemistry and western blot. We analyzed fifteen cases of tumors with challenging histological or clinical differential diagnoses showing respectively a papillary architecture or periventricular location (PGNT mimics). fluorescence in situ hybridization analysis revealed a constant SLC44A1-PRKCA fusion signal in all PGNTs. None of PGNT mimics showed the SLC44A1-PRKCA fusion signal pattern. All PGNTs were negative for BRAF V600E and FGFR1 mutation, and KIAA1549-BRAF fusion. Phospho-ERK analysis provides arguments for the activation of the MAPK signaling pathway in these tumors.

CONCLUSIONS

Here we confirmed and extended the molecular data on PGNT. These results suggest that PGNT belong to low grade glioma with MAPK signaling pathway deregulation. SLC44A1-PRKCA fusion seems to be a specific characteristic of PGNT with a high diagnostic value and detectable by FISH.

The Continuing Value of Ultrastructural Observation in Central Nervous System Neoplasms in Children

Central nervous system (CNS) neoplasms are the second most common childhood malignancy after leukemia and the most common solid organ neoplasm in children. Diagnostic dilemmas with small specimens from CNS neoplasms are often the result of multifactorial etiologies such as frozen or fixation artifact, biopsy size, or lack of knowledge about rare or unfamiliar entities. Since the late 1950s, ultrastructural examination has been used in the diagnosis of CNS neoplasms, though it has largely been replaced by immunohistochemical and molecular cytogenetic studies. Nowadays, pathologic diagnosis of CNS neoplasms is achieved through intraoperative cytology, light microscopy, immunohistochemistry, and molecular cytogenetic results. However, the utility of electron microscopy (EM) in the final diagnosis of CNS neoplasms and investigation of its pathogenetic origin remains critical. Here, we reviewed the distinguishing ultrastructural features of pediatric CNS neoplasms and emphasize the continuing value of EM in the diagnosis of CNS neoplasms.

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.

Clinical, radiological, and pathological features of 16 papillary glioneuronal tumors

BACKGROUND

Papillary glioneuronal tumors (PGNTs) are a novel distinct intracranial neoplastic entity. In this study, the authors aimed to analyze the clinical, radiological, and pathological features of PGNT.

METHODS

Clinical charts and radiographs of 16 cases of PGNT surgically treated between 2006 and 2013 were retrospectively reviewed. Follow-up evaluations and a literature review were performed.

RESULTS

The study included nine males and seven females with a mean age of 23.8 years. The most common preoperative symptom was headache (68.8 %, 11 of 16 patients). Radiological results showed that the frontal lobe (25.0 %) was the most common portion of the brain involved, and 13 lesions (81.3 %) presented with cystic appearance with or without solid elements. All patients were misdiagnosed as non-PGNT tumors. Complete resection was achieved in 12 patients (75.0 %). Ki67 staining was positive in <1 % of cells present in eight lesions and varied in the other eight lesions, with a range of 1 % to 13 %. The mean follow-up duration was 56.2 months, and no recurrence was observed. Seventy-seven PGNTs (40 males, 51.9 %) have been reported, and 49 patients stained positive for Ki67/MIB-1. Of these cases, 28 (57.1 %) had positive staining rates of ≥1 %. In 51 patients for whom outcome information was available, six (11.8 %) exhibited recurrence, and the recurrence rates for complete resection and incomplete resection were 5.1 % and 33.3 %, respectively.

CONCLUSIONS

PGNTs displayed a wide spectrum of clinical and radiological phenotypes, and they were more frequently observed in the frontal lobe and in young patients without sex predilection. Fair outcomes could be achieved by complete resection. Although PGNT displayed indolent pathobiology, atypical appearances were observed. More patients and longer follow-up periods are needed to further elucidate the biological features of PGNTs.

Papillary glioneuronal tumor--a rare entity: report of four cases and brief review of literature

PURPOSE

Papillary glioneuronal tumors (PGNT) have been recently included as a distinct entity in the WHO classification of tumors of the central nervous system. Their molecular pathogenesis is not clear. In the current study, we present the morphological, immunohistochemical, and molecular features of four cases of PGNT reported over the past 11 years.

METHODS

Over a period of 11 years (January 2000-February 2010), there were four cases of PGNT, which were reviewed for histomorphological features. TP53 and IDH1 mutations were assessed using antibodies against p53 protein and for mutant IDH1(R132H) protein, respectively. Immunohistochemistry was also performed for epidermal growth factor receptor (EGFR) protein. Fluorescence in situ hybridization assay was used for analyzing 1p/19q deletion status.

RESULTS

All the tumors showed the characteristic biphasic morphology. Rare findings included minigemistocyte-like cells in one, angiomatous areas in three, focal necrosis in one, and a high MIB-1 labeling index of 12 and 13 %, respectively, in two of the cases. All lacked EGFR, IDH1 expression, and 1p/19q deletions. Interestingly, antibody for p53 labeled the tumor cells, mainly those showing glial differentiation, in two cases. At a mean follow-up of 30 months, there was no evidence of disease progression except in one case which recurred after 24 months.

CONCLUSION

PGNT are rare CNS neoplasms. Despite showing focal morphological features reminiscent of oligodendroglial tumors and presence of astrocytic component, they usually lack the common genetic alterations involved in the pathogenesis of gliomas. Multi-institutional pooling of cases may aid in elucidating their oncogenetic pathway.

Long-term epilepsy-associated tumors

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

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.

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.

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.

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.

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.

Papillary glioneuronal tumor: a case report and review of the literature

Papillary glioneuronal tumor is a recently described central nervous system neoplasm that almost always occurs adjacent to the lateral ventricle. We present a case of this rare entity, representing the 21st case of this lesion, which exhibits a mixed astrocytic and neuronal differentiation. This case was an incidental finding in a young woman who presented secondary to a traumatic injury to the left eye. Histologic evaluation after surgical removal showed a cystic tumor consisting of 2 distinct components: a unique pseudopapillary architecture admixed with foci of solid areas. The pseudopapillae were composed of thick hyalinized vessels enclosed by a single layer of glial fibrillary acid protein-positive astrocytes and variously sized synaptophysin-positive and chromogranin-negative neuronal cells in the interpapillary regions. Abundant Rosenthal fibers, foci of calcification, areas of hemosiderin deposition, gliosis, areas of vascular proliferation associated with piloid gliosis, and chronic inflammatory infiltrate were identified. The combination of cytologic benignity, lack of necrosis, and low proliferative index as evidenced by immunohistochemistry using antibody to Ki-67 confirmed the low malignant potential of this tumor. Knowledge and precise classification of this entity are important to avoid unnecessary use of chemo- and/or radiotherapy for treatment.

Papillary glioneuronal tumor radiologically mimicking a cavernous hemangioma with hemorrhagic onset

Papillary glioneuronal tumor is a recently identified low-grade brain neoplasm classified as variant of ganglioglioma. Its salient morphological characteristics are the presence of pseudopapillary structures composed of blood vessels, often hyalinized, lined by uniform small astrocytes and a proliferation of neurocytic cells, eventually admixed with ganglioid and ganglion cells. We present a case of papillary glioneuronal tumor occurring in a 15-year-old female with an unusual hemorrhagic onset. The clinical, morphological and immunohistochemical features are discussed and the published literature is reviewed. This article proposes that papillary glioneuronal tumor should be included in the differential diagnosis of patients with tumoral related brain hemorrhage.

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.

Papillary glioneuronal tumor: A clinicopathological and immunohistochemical study of two cases

Papillary glioneuronal tumor (PGNT) has recently been identified as a new variant of mixed neuronal-glial tumors. We report the clinical and pathological features of PGNT in two Chinese patients. One patient was a 35-year-old man who suffered from intractable seizures for 16 years. Another was a 26-year-old woman who presented with headache for 2 years. In both patients, magnetic resonance imaging showed well demarcated, mixed cystic and solid tumor in the temporal lobe. Histology of the excised tumors revealed a pseudopapillary architecture surrounded by a glial component and intervening areas were occupied by neuronally differentiated cells. No cortical dysplasia was found in the neighboring cortex in one of them. The glial component showed immunoreactivity with glial fibrillary acidic protein and S-100 protein. Neuronally differentiated cells were immunolabeled by antisynaptophysin, NF, NeuN and MAP2 antibodies. Some small cells surrounding the surface of the pseudopapillae and in the compact area were immunopositive for Olig2. The MIB-1 labeling index was < 3%. The tumor did not recur within the follow-up periods of 50 months and 13 months, and the patient with temporal lobe epilepsy became seizure-free after surgery.

Papillary Glioneuronal Tumor

OBJECTIVE AND IMPORTANCE

Papillary glioneuronal tumor is a recently described neoplasm composed of gliovascular pseudopapillae associated with intervening neuronal cells ranging from neurocytes to ganglion cells. This tumor is not currently included in the WHO classification of tumors of the central nervous system. We describe a new case of papillary glioneuronal tumor and analyze the data for a series of further 15 patients from international literature.

CLINICAL PRESENTATION

A 27-year-old man presented to us for generalized seizure. CT and MRI showed a cystic tumor with mural nodule in the left frontal lobe.

INTERVENTION

Frontal craniotomy with gross total removal of the tumor was performed. Histopathological examination was positive for papillary glioneuronal tumor.

CONCLUSION

The clinical, radiologic, and pathological features of our case are strikingly similar to those of the previous reported cases. A review of the literature disclosed only 15 other cases of these tumors. It is important that every new case of PGNT is reported to allow its recognition and classification.

Papillary glioneuronal tumor with minigemistocytic components and increased proliferative activity

Papillary glioneuronal tumor (PGNT) is a rare and new type of glioneuronal neoplasm of the central nervous system. It is characterized by pseudopapillary structures composed of hyalinized vessels rimmed by cuboidal glial cells and the proliferation of neuronal cells. We report a peculiar PGNT arising in the parietal lobe of a 67-year-old man, which was characterized by proliferation of minigemistocytic cells as well as typical components. The minigemistocytic cells had eccentric nuclei and plump eosinophilic cytoplasm that was filled with glial filaments. The Ki-67 labeling index was as high as 10% in the minigemistocytic areas. Recently, the presence of oligodendroglial-like component was suggested in PGNT. Considering that oligodendroglioma sometimes accompanies minigemistocytic components, the minigemistocytic cells in PGNT were suggested to be a part of oligodendroglial differentiation. Although PGNT is defined as an indolent glioneuronal tumor, the presence of minigemistocytic components with the high Ki-67 labeling index may indicate more aggressive nature.

Papillary glioneuronal tumor

The descriptive term papillary glioneuronal tumor (PGNT) has been repeatedly applied to a morphologic subset of low-grade mixed glial-neuronal neoplasia of juvenile and young adult patients. We report on a 13-year-old boy with PGNT of the left temporal lobe, who presented with headaches and a single generalized seizure. On magnetic resonance imaging, tumor was seen as a large, moderately enhancing paraventricular mass with cyst-mural nodule configuration and slight midline shift. Perifocal edema was virtually absent. Gross total resection could be performed, followed by an uneventful recovery. Histologically, the tumor exhibited similar, if not identical, features as reported previously. These comprised a patterned biphasic mixture of sheets of synaptophysin-expressing small round cells and pseudorosettes of GFAP-positive rudimentary astrocytes along vascular cores. Focally, the latter imprinted a pseudopapillary aspect on this otherwise solid lesion. Both cellular components expressed non-polysialylated neural cell adhesion molecule (NCAM)-L species, and several overlapping areas of synaptophysin and GFAP immunoreactivity were present. The mean MIB-1 labeling index remained below 1%. Signs of anaplasia, in particular mitotic figures, endothelial proliferation, or necrosis were consistently lacking. We perceive PGNT as a clinically and morphologically well-delineated subgroup of extraventricular neurocytic neoplasia, whose paradigmatic presentation may allow for consideration as an entity.

Newly defined central nervous system neoplasms

In recent years, numerous new entities or variants of recognized central nervous system tumors have been described in the literature, and the morphologic spectrum of these neoplasms is delineated incompletely. The accurate diagnosis and classification of these lesions is important to ensure that patients receive adequate therapy and prognostic information. The clinicopathologic features and differential diagnosis of 4 new entities, including the chordoid glioma of the third ventricle, cerebellar liponeurocytoma, atypical teratoid/rhabdoid tumor, and papillary glioneuronal tumor, are discussed in this review.

A distinct pattern of Olig2-positive cellular distribution in papillary glioneuronal tumors: a manifestation of the oligodendroglial phenotype?

Mixed neuronal-glial tumors of the central nervous system display a wide spectrum of differentiation. Among them, the papillary glioneuronal tumor (PGNT) is characterized by pseudopapillary structures composed of astroglial cells covering hyalinized vessels, and by neurocytic, ganglioid and ganglion cells. In addition, a "nonspecific" cell type, not similar to either astrocytes or neurocytes, has been recognized since the initial reports. Recently, minigemistocytic cells and a population immunostained by anti-Olig2 antibody have also been recognized in PGNT. Olig2 is a transcription factor that is specific for the cellular phenotype of oligodendrocytes. The aim of this study was to further investigate the histological diversity of PGNT. We examined six cases of PGNT, each of which showed Olig2 immunopositivity. Minigemistocytes were encountered in three cases at close proximity to the Olig2-positive area. Olig2-positive cells were negative for glial fibrillary acidic protein (GFAP) and neuronal nuclear antigen by double immunostaining, and mainly occupied the interpapillary area laterally adjacent to the GFAP-positive cells. They had relatively small, round and vesicular nuclei, and were formerly regarded as neurocytic cells or nonspecific cellular elements. Fluorescence in situ hybridization targeting chromosome 1p failed to demonstrate any deletion. This study disclosed an additional cellular component of PGNT that is characterized by Olig2 positivity, suggestive of oligodendroglial phenotype, and the results also encourage us to investigate oligodendroglial participation in various glioneuronal tumors.

Long term follow-up in a patient with papillary glioneuronal tumor

We report a case of a young female patient with a rare and recently described form of brain tumor. This patient had a history of headache, hemiparesis and motor simple partial seizures. Her investigation revealed a brain tumor involving the left frontal and parietal lobes. The radiological images showed a cystic mass with multiple nodular masses and a rim of contrast enhancement extending from the right parietal cortex to the ipsilateral ventricle and corpus callosum. The patient underwent gross resection of the lesion and the histological analysis of the surgical specimen revealed a pseudopapillary structure formed by delicate vessels intermixed with a fibrillary pattern and bordered by intense astrocytic reaction with Rosenthal fibers. These features correspond to the recently described mixed neuronal-glial neoplasm, the papillary glioneuronal tumor. The patient has been followed for five years since the surgical treatment, without evidence of tumor recurrence, confirming the indolent behavior of this type of tumor.

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.

A papillary glioneuronal tumor arising in an elderly woman: a case report

The papillary glioneuronal tumor (PGNT) was first reported by Komori et al. as a type of mixed neuronal-glial tumor. It is characterized by pseudopapillary structures, composed of hyaline vessels and outsheathing glial cells, and by the proliferation of neurocytic cells admixed with ganglioid and ganglion cells. Although it is most common in young adults, it can occur in the elderly. We report a case in a 75-year-old woman, the oldest reported person with PGNT described.