Ependymomas with neuronal differentiation: a morphologic and immunohistochemical spectrum

Immunohistochemical analyses of neural stem cell lineage markers in normal feline brains and glial tumors

Neural stem cell (NSC) lineage cells have not been fully identified in feline brains, and the NSC-like nature of feline glial tumors has not been determined. In this study, 6 normal cat brains (3 newborn and 3 older cats) and 13 feline glial tumors were analyzed using immunohistochemical NSC lineage markers. The feline glial tumors were subjected to immunohistochemical scoring followed by hierarchical cluster analysis. In newborn brains, glial acidic fibrillary protein (GFAP)/nestin/sex-determining region Y-box transcription factor 2 (SOX2)-immunopositive NSCs, SOX2-immunopositive intermediate progenitor cells, oligodendrocyte transcription factor 2 (OLIG2)/platelet-derived growth factor receptor-α (PDGFR-α)-immunopositive oligodendrocyte precursor cells (OPCs), OLIG2/GFAP-immunopositive immature astrocytes, and neuronal nuclear (NeuN)/β-3 tubulin-immunopositive mature neuronal cells were observed. The apical membrane of NSCs was also immunopositive for Na+/H+ exchanger regulatory factor 1 (NHERF1). In mature brains, the NSC lineage cells were similar to those of the newborn brains. A total of 13 glial tumors consisted of 2 oligodendrogliomas, 4 astrocytomas, 3 subependymomas, and 4 ependymomas. Astrocytomas, subependymomas, and ependymomas were immunopositive for GFAP, nestin, and SOX2. Subependymomas and ependymomas showed dot-like or apical membrane immunolabeling for NHERF1, respectively. Astrocytomas were immunopositive for OLIG2. Oligodendrogliomas and subependymomas were immunopositive for OLIG2 and PDGFR-α. Feline glial tumors also showed variable immunolabeling for β-3 tubulin, NeuN, and synaptophysin. Based on these results, feline astrocytomas, subependymomas, and ependymomas appear to have an NSC-like immunophenotype. In addition, astrocytomas, subependymomas, and ependymomas have the characteristics of glial, oligodendrocyte precursor, and ependymal cells, respectively. Feline oligodendrogliomas likely have an OPC-like immunophenotype. In addition, feline glial tumors may have multipotential stemness for differentiation into neuronal cells. These preliminary results should be validated by gene expression analyses in future studies with larger case numbers.

Benign Spinal Tumors

Benign spinal intradural tumors are relatively rare and include intramedullary tumors with a favorable histology such as low-grade astrocytomas and ependymomas, as well as intradural extramedullary tumors such as meningiomas and schwannomas. The effect on the neural tissue is usually a combination of mass effect and neuronal involvement in cases of infiltrative tumors. The new understanding of molecular profiling of different tumors allowed us to better define central nervous system tumors and tailor treatment accordingly. The mainstay of management of many intradural spinal tumors is maximal safe surgical resection. This goal is more achievable with intradural extramedullary tumors; yet, with a meticulous surgical approach, many of the intramedullary tumors are amenable for safe gross-total or near-total resection. The nature of these tumors is benign; hence, a different way to measure outcome success is pursued and usually depends on functional rather than oncological or survival outcomes.

Supratentorial ependymoma, zinc finger translocation-associated fusion positive, with extensive synaptophysin immunoreactivity arising from malignant transformation of clear cell ependymoma: A case report

Background:

We describe a case of a supratentorial ependymoma, zinc finger translocation-associated (ZFTA) fusion positive with extensive synaptophysin immunoreactivity arising from malignant transformation of an ependymoma with clear cell features in a patient with long-term follow-up.

Case Description:

A 55-year-old woman presented with seizures and ataxia 15 years after an initial resection of a clear cell ependymoma, Grade 2. Imaging demonstrated an enhancing right paracentral mass and the patient underwent biopsy and resection. Microscopic analysis showed regions of the tumor with morphological and immunohistochemical features typical of ependymoma, including perivascular pseudorosettes and focal dot- like epithelial membrane antigen positivity, as well as high-grade features. In addition, the neoplasm contained large nodular regions of clear cells exhibiting extensive synaptophysin immunoreactivity, suggestive of neural differentiation, and only focally positive immunoreactivity for glial markers. Electron microscopy showed poorly formed and ill-defined junctional complexes, but no cilia, microvilli, or dense granules were seen. Molecular profiling revealed the presence of a fusion between ZFTA (previously known as C11orf95) and RELA fusion.

Conclusion:

We report a case of extensive synaptophysin immunoreactivity in a ZFTA-RELA fusion-positive ependymoma that had undergone malignant transformation from a clear cell ependymoma and has long-term follow-up, contributing to the assessment of prognostic significance of synaptophysin immunoreactivity in supratentorial ependymoma, ZFTA fusion positive.

Sarcomatous Change of Cerebellopontine Angle Ependymoma Following Radiosurgery: A Case Report

Sarcomatous change in ependymal tumors is rare and has been poorly described. We report on a cerebellopontine angle lesion that demonstrated rapid progression two years after radiosurgery in a 73-year-old female patient. Histopathological diagnosis at clinical progression showed an ependymoma with sarcomatous change (“ependymosarcoma”) that was believed to be due to radiation. The patient underwent a complex tumor resection without complications using an exhaustive multi-modal neuromonitoring paradigm throughout the dissection and resection of the tumor. Given the limited available data on these rare tumors, we review their presentation, imaging, and histopathology in the context of the previous literature, and also discuss the management of these lesions in the cerebellopontine angle.

NordiQC Assessments of Synaptophysin Immunoassays

This paper is number 8 in a series developed through a partnership between ISIMM and NordiQC with the purpose of reporting research assessing the performance characteristics of immunoassays in an external proficiency testing program.

Adult WHO grade II ependymomas: is Ki67 a sex-specific proliferation marker?

Ki67 is a marker for proliferation of a given cell population. Low expression of Ki67 may be associated with a favourable outcome. We investigate how the proliferation index correlates with the location, morphology and behaviour of WHO grade II ependymomas with a single-centre cohort study of adult patients admitted for surgery of WHO grade II ependymomas between 2008 and 2018.

Seventeen patients were included, seven had supratentorial and 10 had infratentorial tumours. Three patients died and eight had recurrent disease. Age, gender, location, extent of resection, chemotherapy, radiotherapy and histological markers were not associated with tumour progression. Both unadjusted and adjusted analysis confirmed a higher Ki67 index in male patients. Sensitivity analysis further supported the correlation between Ki67 and male gender.

Ki67 may be sex specific but does not seem to correlate with survival and time to recurrence in this series.

L1CAM Immunopositivity in Anaplastic Supratentorial Ependymomas: Correlation With Clinical and Histological Parameters

Supratentorial ependymomas (ST EPNs) are molecularly characterized, of which the RELA fusion positive tumors are the most common and aggressive subgroup. Moreover, histologically, anaplastic ST EPN (ST-AE) often mimic other central nervous system primary high-grade tumors resulting in a diagnostic dilemma. We aimed to study a cohort of ST-AE; evaluate the expression of two RELA fusion-associated markers—L1CAM and p65 (NF-κB); and correlate their expression with clinical and histological parameters. Cases of ST-AE diagnosed in our department from January 2011 to June 2016 (n = 72) were reviewed. A battery of immunohistochemical markers was employed. A total of 65 confirmed ST-AE were included in the study. Age ranged from 9 months to 60 years. There was a slight predominance in the pediatric population (57%). Male-to-female ratio was 1:1.16. Histomorphological features were varied and mimicked other high-grade tumors in several cases. L1CAM immunopositive tumors constituted 26% of cases and were predominantly seen in young children, in the frontoparietal location, and exhibited clear cell morphology with calcification. A consistent pattern of L1CAM immunopositivity was noted in paired primary and recurrent tumor samples. Our study portrays the varied clinical and histomorphological spectrum of ST-AE. The study emphasizes the association of L1CAM immunopositivity with a wide spectrum of histological parameters, literature on which is scant till date. Since ST EPN-RELA are tumors with aggressive behavior, such a correlation would be clinically relevant, particularly when there is limited access to molecular testing.

The 2016 WHO Classification of Tumours of the Central Nervous System: The Major Points of Revision

The updated 2016 edition of the World Health Organization (WHO) Classification of Tumours of the Central Nervous System (CNS) uses molecular parameters and the histology to define the main tumor categories for the first time. This represents a shift from the traditional principle of using neuropathological diagnoses, which are primarily based on the microscopic features, to using molecularly-oriented diagnoses. Major restructuring was made with regard to diffuse gliomas, medulloblastomas and other embryonal tumors. New entities that are defined by both the histological and molecular features include glioblastoma, isocitrate dehydrogenase (IDH)-wildtype and glioblastoma, IDH-mutant; diffuse midline glioma, H3 K27M-mutant; RELA fusion-positive ependymoma; medulloblastoma, wingless (WNT)-activated and medulloblastoma, sonic hedgehog (SHH)-activated; and embryonal tumor with multilayered rosettes, C19MC-altered. In addition, some entities that are no longer diagnostically relevant—such as CNS-primitive neuroectodermal tumor—have been deleted from this updated edition. The WHO2016 certainly facilitates clinical and basic research to improve the diagnosis of brain tumors and patient care.

Anaplastic Ependymoma With Ganglionic Differentiation: Report of a Rare Case and Implications in Diagnosis

Ependymomas are glial neoplasms with rare cases exhibiting neuronal differentiation. We describe a case of spinal anaplastic ependymoma with ganglionic differentiation in a 28-year-old woman. The ganglionic component was labeled by synaptophysin, whereas the rest of the tumor showed features of an anaplastic ependymoma. Stem cell marker MELK was noted to stain both the neoplastic ependymal and ganglionic components, possibly suggesting a stem cell/progenitor origin for the tumor with subsequent divergent differentiation.

Histologic classification of gliomas

Gliomas form a heterogeneous group of tumors of the central nervous system (CNS) and are traditionally classified based on histologic type and malignancy grade. Most gliomas, the diffuse gliomas, show extensive infiltration in the CNS parenchyma. Diffuse gliomas can be further typed as astrocytic, oligodendroglial, or rare mixed oligodendroglial-astrocytic of World Health Organization (WHO) grade II (low grade), III (anaplastic), or IV (glioblastoma). Other gliomas generally have a more circumscribed growth pattern, with pilocytic astrocytomas (WHO grade I) and ependymal tumors (WHO grade I, II, or III) as the most frequent representatives. This chapter provides an overview of the histology of all glial neoplasms listed in the WHO 2016 classification, including the less frequent "nondiffuse" gliomas and mixed neuronal-glial tumors. For multiple decades the histologic diagnosis of these tumors formed a useful basis for assessment of prognosis and therapeutic management. However, it is now fully clear that information on the molecular underpinnings often allows for a more robust classification of (glial) neoplasms. Indeed, in the WHO 2016 classification, histologic and molecular findings are integrated in the definition of several gliomas. As such, this chapter and Chapter 6 are highly interrelated and neither should be considered in isolation.

Malignant Glioma with Neuronal Marker Expression : A Clinicopathological Study of 18 Cases

Objective

Malignant gliomas with neuronal marker expression (MGwNM) are rare and poorly characterized. Increasingly diverse types of MGwNM have been described and these reported cases underscore the dilemmas in the classification and diagnosis of those tumors. The aim of this study is to provide additional insights into MGwNM and present the clinicopathological features of 18 patients.

Methods

We reviewed the medical records of 18 patients diagnosed as MGwNM at our institute between January 2006 and December 2012. Macroscopic total resection was performed in 11 patients (61%). We evaluated the methylation status of O⁶-methylguanine-DNA methyltransferase (MGMT) and expression of isocitrate dehydrogenase 1 (IDH-1) in all cases, and deletions of 1p and 19q in available cases.

Results

The estimated median overall survival was 21.2 months. The median progression-free survival was 6.3 months. Six patients (33%) had MGMT methylation but IDH1 mutation was found in only one patient (6%). Gene analysis for 1p19q performed in nine patients revealed no deletion in six, 19q deletion only in two, and 1p deletion only in one. The extent of resection was significantly correlated with progression free survival on both univariate analysis and multivariate analysis (p=0.002 and p=0.013, respectively).

Conclusion

In this study, the overall survival of MGwNM was not superior to glioblastoma. The extent of resection has a significant prognostic impact on progression-free survival. Further studies of the prognostic factors related to chemo-radio therapy, similar to studies with glioblastoma, are mandatory to improve survival.

Glioneuronal tumours with features of rosette-forming glioneuronal tumours of the fourth ventricle and dysembryoplastic neuroepithelial tumours: a report of three cases

AIMS

To study three atypical glioneuronal tumours (GNTs), in order to shed light on the clinical and pathological features of this diverse tumour group.

METHODS AND RESULTS

Clinical and neuropathological data for each case were retrospectively reviewed. Case 1 involved a 17-year-old boy with left leg movement difficulty. A mass lesion in the basal ganglia was detected radiologically; histopathological features included neurocytic/perivascular rosettes and a pilocytic astrocytoma component. Case 2 involved a 33-year-old man with intractable epilepsy. His left parietal lobe contained a cyst-like mass, resembling dysembryoplastic neuroepithelial tumour and rosette-forming glioneuronal tumour of the fourth ventricle microscopically. Case 3 involved a 21-year-old woman with a mass lesion in the mesencephalic tegmentum extending to the third and fourth ventricles and the suprasellar region. The lesion contained perivascular/neurocytic rosettes and an oligodendroglioma-like component. None of the tumours expressed an isocitrate dehydrogenase I mutation of the R132H type or contained a 1p/19q deletion, a BRAF(V600E) mutation, or KIAA1549-BRAF fusion.

CONCLUSIONS

We describe three GNTs with atypical histopathology and locations. Additional cases and molecular studies are needed to better understand the biological nature of GNTs and to refine their classification system.

Promoted Growth of Brain Tumor by the Transplantation of Neural Stem/Progenitor Cells Facilitated by CXCL12

The targeted migration of neural stem/progenitor cells (NSPCs) is a prerequisite for the use of stem cell therapy in the treatment of pathologies. This migration is regulated mainly by C-X-C motif chemokine 12 (CXCL12). Therefore, promotion of the migratory responses of grafted cells by upregulating CXCL12 signaling has been proposed as a strategy for improving the efficacy of such cell therapies. However, the effects of this strategy on brain tumors have not yet been examined in vivo. The aim of the present study was thus to elucidate the effects of grafted rat green fluorescent protein (GFP)-labeled NSPCs (GFP-NSPCs) with CXCL12 enhancement on a model of spontaneous rat brain tumor induced by N-ethyl-N-nitrosourea. T2-weighted magnetic resonance imaging was applied to determine the changes in tumor volume and morphology over time. Postmortem histology was performed to confirm the tumor pathology, expression levels of CXCL12 and C-X-C chemokine receptor type 4, and the fate of GFP-NSPCs. The results showed that the tumor volume and hypointense areas of T2-weighted images were both significantly increased in animals treated with combined NSPC transplantation and CXCL12 induction, but not in control animals or in those with tumors that received only one of the treatments. GFP-NSPCs appear to migrate toward tumors with CXCL12 enhancement and differentiate uniquely into a neuronal lineage. These findings suggest that CXCL12 is an effective chemoattractant that facilitates exogenous NSPC migration toward brain tumors and that CXCL12 and NSPC can act synergistically to promote tumor progression with severe hemorrhage.

Anaplastic ependymoma of the third ventricle

Supratentorial ependymomas are rare, especially in the third ventricle. We report the case of an ependymoma of the posterior third ventricle that was endoscopically removed just by aspiration through a flexible scope. Histologically, beside the typical pattern of growth with perivascular pseudorosettes, the tumor featured hypercellular areas with more than 10 mitoses per 10 high-power fields, consistent with grade III-anaplastic tumor. A few months later, a second neuroendoscopy offered the unique chance to appreciate the total absence of tumor tissue and the restored anatomy. However, consistently with the high grade, the tumor recurred in two different locations including the endoscopic trajectory, and spread through the cerebrospinal fluid. The patient underwent a second resective surgery and radiosurgery. Despite a cycle of chemotherapy, multiple lesions both in the ventricular system and at the level of cauda equina appeared 12 months later. A comprehensive review of intraventricular anaplastic ependymomas is also provided.

A case of oligodendroglioma with prominent neuronal differentiation

We report a case of oligodendroglioma showing marked neuronal differentiation, which arose in the right frontal lobe of a 46-year-old woman. The resected tumor was composed of a mixture of oligodendroglioma, gangliocytoma, and neurocytoma areas with predominance of gangliocytoma-like areas. The oligodendroglioma areas showed immunoreactivity for Olig2 and mutant isocitrate dehydrogenase 1 protein, whereas the gangliocytoma and neurocytoma areas were positive for synaptophysin and NeuN. Ki-67 labeling index was approximately 5% to 10% in the oligodendroglioma areas. Molecular cytogenetic analyses demonstrated chromosomal losses of 1p and 19q and a mutation of isocitrate dehydrogenase 1 (G395A, R132H) in both the oligodendroglioma and gangliocytoma areas. These data suggest that this tumor is an oligodendroglioma associated with prominent neuronal differentiation. There seems to be a close relationship between oligodendroglial progenitor cells and neuronal cells.

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.

Supra- and infratentorial pediatric ependymomas differ significantly in NeuN, p75 and GFAP expression

Ependymomas comprise 8 % of all intracranial tumors in children <15 years. Recent studies revealed that some supratentorial ependymomas express neuronal antigens and that high expression of neurofilament protein light polypeptide (NEFL) correlates with better clinical outcome. We retrospectively analyzed an expanded panel of proteins in 6 supratentorial, 15 posterior fossa and 4 spinal pediatric ependymomas by immunohistochemistry. Expression of high and low affinity neurotrophin receptors TrkA (NTRK1) and p75 (NGFR), pan-neuronal markers NeuN (RBFOX3) and synaptophysin, radial glial marker SOX9, adhesion molecules CD56 (NCAM) and CD44, junctional protein connexin 43 (GJA1), glial fibrillary acidic protein (GFAP), epithelial membrane antigen and proliferation associated antigen Ki-67 were evaluated in a semi-quantitative or quantitative (Ki-67 and NeuN-index) fashion. We found p75 and NeuN to be expressed at significantly higher levels in supratentorial versus infratentorial tumors and GFAP to be expressed at significantly higher levels in infratentorial lesions. In conclusion, immunohistochemical expression of p75, NeuN and GFAP differed in ependymomas depending on tumor topography supporting the view of divergent cells of origin. However, because of the small sample size the results are of preliminary nature and replication in a larger cohort would be desirable.

Prognostic significance of neuronal marker expression in glioblastomas

PURPOSE

Glioblastomas are the most malignant tumors of central nervous system neoplasms and are well known for their biological heterogeneity. Contrary to the putative hypothesis of purely glial differentiation in glioblastomas, they often demonstrate immunopositivity for neuronal markers. However, the significance of their neuronal marker expression is still controversial. To evaluate the prognostic implication of neuronal expression in glioblastoma, this study investigated the expression of neuronal markers in a large series of glioblastoma patients in terms of patient survival rate.

METHODS

Expression of synaptophysin, neurofilament protein, and NeuN was explored using immunohistochemistry in 88 cases of glioblastoma. Clinicopathological variables as well as patients' survival data were compared according to the immunopositivity of cases.

RESULTS

Sixty-one of the 88 tumors (69.3 %) were positive for at least one neuronal marker. Synaptophysin positivity was observed in 43 cases (48.9 %). Neurofilament protein and NeuN were positive in 38 (43.2 %) and 42 cases (47.7 %), respectively. There was no statistically significant difference in overall survival and progression-free survival in association with neuronal marker expression. However, gross total removal or combined radiotherapy and chemotherapy significantly prolonged survival (P=0.041 and 0.044). Cox's proportional hazard model revealed that NeuN expression was the independent prognostic factors in progression-free survival (P=0.012).

CONCLUSIONS

Although the correlation of neuronal marker expression and clinical outcome in glioblastoma is of considerable interest, the presented data support the limited prognostic value of neuronal marker expression in glioblastoma.

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.

Neuronal markers are expressed in human gliomas and NSE knockdown sensitizes glioblastoma cells to radiotherapy and temozolomide

BACKGROUND

Expression of neuronal elements has been identified in various glial tumors, and glioblastomas (GBMs) with neuronal differentiation patterns have reportedly been associated with longer survival. However, the neuronal class III β-tubulin has been linked to increasing malignancy in astrocytomas. Thus, the significance of neuronal markers in gliomas is not established.

METHODS

The expressions of class III β-tubulin, neurofilament protein (NFP), microtubule-associated protein 2 (MAP2) and neuron-specific enolase (NSE) were investigated in five GBM cell lines and two GBM biopsies with immunocytochemistry and Western blot. Moreover, the expression levels were quantified by real-time qPCR under different culture conditions. Following NSE siRNA treatment we used Electric cell-substrate impedance sensing (ECIS) to monitor cell growth and migration and MTS assays to study viability after irradiation and temozolomide treatment. Finally, we quantitated NSE expression in a series of human glioma biopsies with immunohistochemistry using a morphometry software, and collected survival data for the corresponding patients. The biopsies were then grouped according to expression in two halves which were compared by survival analysis.

RESULTS

Immunocytochemistry and Western blotting showed that all markers except NFP were expressed both in GBM cell lines and biopsies. Notably, qPCR demonstrated that NSE was upregulated in cellular stress conditions, such as serum-starvation and hypoxia, while we found no uniform pattern for the other markers. NSE knockdown reduced the migration of glioma cells, sensitized them to hypoxia, radio- and chemotherapy. Furthermore, we found that GBM patients in the group with the highest NSE expression lived significantly shorter than patients in the low-expression group.

CONCLUSIONS

Neuronal markers are aberrantly expressed in human GBMs, and NSE is consistently upregulated in different cellular stress conditions. Knockdown of NSE reduces the migration of GBM cells and sensitizes them to hypoxia, radiotherapy and chemotherapy. In addition, GBM patients with high NSE expression had significantly shorter survival than patients with low NSE expression. Collectively, these data suggest a role for NSE in the adaption to cellular stress, such as during treatment.

Mutation-specific IDH1 antibody differentiates oligodendrogliomas and oligoastrocytomas from other brain tumors with oligodendroglioma-like morphology

Isocitrate dehydrogenase 1 (IDH1) mutations are frequent in astrocytomas, oligoastrocytomas and oligodendrogliomas. We previously reported the generation of a mutation-specific antibody that specifically detects R132H mutated IDH1 protein (clone H09). Here, we investigate the feasibility of H09 immunohistochemistry to differentiate between oligodendrogliomas/oligoastrocytomas and other tumors with similar morphology. A total of 274 brain tumors presenting with focal or extensive clear cell morphology were investigated. High numbers of H09-positive cases were observed in adult grade II oligodendrogliomas (67 of 74, 91%), grade III oligodendrogliomas (65 of 69, 94%), grade II oligoastrocytomas (11 of 14, 79%) and grade III oligoastrocytomas (10 of 11, 91%). All cases of pediatric oligodendrogliomas (n = 7), neurocytomas (n = 41, 35 central, 4 extraventricular, 2 cerebellar liponeurocytomas), dysembryoplastic neuroepithelial tumors (n = 21), clear cell ependymomas (n = 8), clear cell meningiomas (n = 9) as well as 12 primary glioblastomas with oligodendroglial differentiation and 5 pilocytic astrocytomas with oligodendroglial-like differentiation were negative for H09 immunohistochemistry. Three oligodendrogliomas with neurocytic differentiation had evidence of IDH1/IDH2 mutations either by H09 immunohistochemistry or direct sequencing. We conclude that in tumors with an oligodendroglioma-like morphology, binding of H09 is highly specific for oligodendrogliomas or oligoastrocytomas and substantially helps in the discrimination from other clear cell tumors. Negative H09 immunohistochemistry of an adult oligodendroglioma or oligoastrocytoma should prompt the consideration of other clear cell neoplasms. Further, our observations firmly assign oligodendrogliomas with neurocytic differentiation to the group of oligodendrogliomas and demonstrate that H09 is especially helpful for the difficult discrimination of such lesions from extraventricular neurocytomas.

Extraventricular anaplastic ependymoma with metastasis to scalp and neck

We report a case of anaplastic ependymoma with extracranial metastases in a 22-year-old female. The patient originally presented with headaches and dysarthria. Neuroimaging revealed a large solid and cystic right fronto-temporal lesion. It was located completely extraventricularly and a glioblastoma was suspected based on the neuroimaging findings. A gross total resection was achieved. Histopathologic examination revealed an anaplastic ependymoma. The patient was treated with radiotherapy. Approximately 1 year after the initial surgery, the patient presented with metastatic disease to the scalp. At 2 years, an intraparotid metastasis was detected. Subsequent neck dissection revealed positive lymph nodes at several levels. It was followed by radiotherapy to the neck. 5 years after the initial surgery, the patient has residual metastatic disease. The case is discussed and the literature on extraventricular ependymal neoplasms is reviewed.

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.

Neural stem cell-like gene expression in a mouse ependymoma cell line transformed by human BK polyomavirus

Ependymomas often show characteristics similar to those of neural stem cells in vivo and in vitro. However, few ependymoma cell lines that exhibit neural stem cell-like properties have been reported. In this study, we have characterized a novel cell line, designated Vn19, established from ependymoma that arose in mice inoculated intracerebrally with human BK polyomavirus. Transplanted Vn19 cells in nude mice ubiquitously expressed viral large T antigen in the nucleus and coexpressed neuronal and glial marker proteins in vivo. Remarkably, individual Vn19 cells in dispersed cultures simultaneously expressed marker proteins of neural stem cells (nestin, Bmi1, CD133), neurons (βIII tubulin, neurofilament-M) and glial cells (glial fibrillary acidic protein, A2B5, S100β, O4). Ubiquitous and homogenous expression of these multilineage marker proteins was also observed in cloned Vn19 cells. The Vn19 cells formed neurosphere-like aggregates when cultured in the presence of growth factors. Quantitative RT-PCR analysis revealed that expression of mRNA for nestin, neurofilament-H and glial fibrillary acidic protein significantly increased in Vn19 cells cultured under growth factor-deprived conditions. Among MAGE (melanoma antigen) family genes, MAGE-A (A1-8), MAGE-B (B1-3), MAGE-D1, MAGE-E1, MAGE-G1 (necdin-like 2) and MAGE-H1 were expressed in the Vn19 cells, in which neither necdin nor MAGEL2 was detectable. These results suggest that this murine ependymoma cell line recapitulates the gene expression profile in ependymal cells undergoing malignant transformation.

Synchronous Choroid Plexus Papilloma of the Fourth Ventricle and Ependymoma of the Filum Terminale: Case Report

BACKGROUND AND IMPORTANCE:

We report the first case of synchronous choroid plexus papilloma of the fourth ventricle and myxopapillary ependymoma of the filum terminale. Both are papillary World Health Organization grade I tumors known to disseminate via cerebrospinal fluid pathways.

CLINICAL PRESENTATION:

A 65-year-old man presented with an incidental mass in the fourth ventricle found on a computed tomography scan of the head after a motor vehicle collision and an intradural mass of the filum terminale. The patient underwent resection of the fourth ventricle mass. After pathological diagnosis of a choroid plexus papilloma, the patient underwent resection of the spinal cord tumor.

CONCLUSION:

This case underscores the need for separate pathological diagnosis in a patient with an intradural spine lesion in the context of a benign intracranial lesion. We detail a panel of immunohistochemical markers essential for distinguishing the 2 papillary neuroectodermal tumors recovered in this case.

Neuronal differentiation distinguishes supratentorial and infratentorial childhood ependymomas

Ependymomas are glial neoplasms occurring in any location throughout the central nervous system and supposedly are derived from radial glia cells. Recent data suggest that these tumors may have different biological and clinical behaviors according to their location. Pediatric supratentorial and infratentorial ependymoma (SE and IE) were compared with respect to clinical and radiological parameters and immunohistochemistry (IHC). Neuronal markers were specifically assessed by IHC and quantitative PCR (qPCR). No single morphological or radiological characteristic was associated with location or any neuronal marker. However, there was a significant overexpression of neuronal markers in SE compared with IE: neurofilament light polypeptide 70 (NEFL)-positive tumor cells were found in 23 of 34 SE and in only 4 of 32 IE (P < .001). Among SE, 10 of 34 exhibited high expression of NEFL, defined as more than 5% positive cells. qPCR confirmed the upregulation of neuronal markers (NEFL, LHX2, FOXG1, TLX1, and NPTXR) in SE compared with IE. In addition, strong NEFL expression in SE was correlated with better progression-free survival (P = .007). Our results support the distinction of SE and IE. SEs are characterized by neuronal differentiation, which seems to be associated with better prognosis.

Glioma diagnosis: immunohistochemistry and beyond

Clinicians and pathologists have been inundated by published reports of new and potentially interesting diagnostic, prognostic, and putative predictive "markers" whose expression (or loss) holds great promise for more enlightened diagnoses and ultimately better patient care. Although an understanding of therapeutically (and possibly diagnostically) relevant pathways of glioblastoma may be at hand, significant challenges remain. Many immunohistochemical and genetic tests have proven to be useful in the stratification of clinical trials, whereas the utility of many others for the day-to-day practice of pathology awaits further study and validation. The importance of critical literature review and careful consideration of practical issues such as test standardization, compliance, cost-effectiveness, and availability must all be considered before implementing any new diagnostic test. This review will focus on the role of immunohistochemistry in the routine diagnosis of astrocytic and oligodendrocytic tumors and in assisting with the diagnosis of some less common gliomas that have ependymal-like features. It will conclude with a summary of molecular and genetic studies, which not only hold great promise for improved diagnosis, but also reveal prognostic information on disease outcome and predict response to treatment or provide biologic targets for novel therapies.

Expression of diagnostic neuronal markers and outcome in glioblastoma

BACKGROUND

High-grade gliomas featuring giant cells, often demonstrate immunoreactivity for neuronal markers, a finding prognostically significant according to some studies. We investigated this event in glioblastomas (GBM).

METHODS

Immunoexpression for synaptophysin, neurofilament protein, neuronal nuclear antigen, chromogranin and glial fibrillary acidic protein was analysed in 82 GBM including 11 fibrillary, 8 gemistocytic, 40 giant cell and 23 small cell examples. Survival was compared between tumours exhibiting (GBMpos) or lacking (GBMneg) neuronal markers and also between tumours expressing only one vs. two or more neuronal markers.

RESULTS

Forty-five of the 82 tumours (54.8%) including 5 fibrillary, 5 gemistocytic, 30 giant cell and 5 small cell GBMs expressed at least one neuronal marker, synaptophysin being the most frequent (96%). There was no statistically significant difference in survival between GBMpos and GBMneg tumours, all cytologic subtypes combined (P = 0.22). The same was true when cytologic categories were compared. When only GBMpos tumours were analysed, there was a marginally significant difference in outcome between tumours positive for one vs. multiple markers (P = 0.05). This difference was influenced primarily by giant cell GBMs among which the survival time was significantly shorter in the multiple vs. single marker category (median 123 vs. 295 days, P = 0.014). This difference was not observed in the other GBM cell types. Ultrastructurally, rare neurosecretory granules in glial filament-rich cells were identified in one of four tumours studied.

CONCLUSIONS

Neuronal marker expression is a frequent feature of GBM. Its prognostic significance is limited to the giant cell GBMs expressing two or more neuronal markers, these being associated with shorter survival.

Rosette-forming glioneuronal tumor: report of an unusual case with intraventricular dissemination

A rosette-forming glioneuronal tumor (RGNT) was encountered in a 16-year-old Chinese girl. She experienced seizures with loss of consciousness for 1 month prior to diagnosis. A brain MRI revealed multifocal masses occupying all of the ventricular system associated with marked hydrocephalus. A biopsy was performed on the right lateral ventricle using a neuroendoscope and the patient was given postoperative radiotherapy. She was followed for 7 months, and there was no radiological or clinical evidence of tumor progression. Histological examination demonstrated two regions characterized by predominant neurocytic rosettes and scant low grade astrocytoma. No histological anaplasia was present. Immunohistological studies showed that the small round tumor cells forming rosettes were strongly positive for Olig2. A chromosome 1p/19q co-deletion was not detected by FISH analysis. While the pathological features of our case closely resembled those reported in the original description, the diffuse intraventricular growth pattern of the tumor was different from previous examples. Further long-term follow-up studies are required to assess the biological behavior and clinical outcome of the RGNT entity.

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.

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.

Ependymal tumors

Ependymomas represent a heterogeneous group of glial tumors whose biological behavior depends on various histological, molecular, and clinical variables. The scope of this chapter is to review the clinical and histo-logical features as well as the molecular genetics of ependymomas with special emphasis on their influence on tumor recurrence and prognosis. Furthermore, potential molecular targets for therapy are outlined.

Donor-derived brain tumor following neural stem cell transplantation in an ataxia telangiectasia patient

BACKGROUND

Neural stem cells are currently being investigated as potential therapies for neurodegenerative diseases, stroke, and trauma. However, concerns have been raised over the safety of this experimental therapeutic approach, including, for example, whether there is the potential for tumors to develop from transplanted stem cells.

METHODS AND FINDINGS

A boy with ataxia telangiectasia (AT) was treated with intracerebellar and intrathecal injection of human fetal neural stem cells. Four years after the first treatment he was diagnosed with a multifocal brain tumor. The biopsied tumor was diagnosed as a glioneuronal neoplasm. We compared the tumor cells and the patient's peripheral blood cells by fluorescent in situ hybridization using X and Y chromosome probes, by PCR for the amelogenin gene X- and Y-specific alleles, by MassArray for the ATM patient specific mutation and for several SNPs, by PCR for polymorphic microsatellites, and by human leukocyte antigen (HLA) typing. Molecular and cytogenetic studies showed that the tumor was of nonhost origin suggesting it was derived from the transplanted neural stem cells. Microsatellite and HLA analysis demonstrated that the tumor is derived from at least two donors.

CONCLUSIONS

This is the first report of a human brain tumor complicating neural stem cell therapy. The findings here suggest that neuronal stem/progenitor cells may be involved in gliomagenesis and provide the first example of a donor-derived brain tumor. Further work is urgently needed to assess the safety of these therapies.

Malignant gliomas with primitive neuroectodermal tumor-like components: a clinicopathologic and genetic study of 53 cases

Central nervous system neoplasms with combined features of malignant glioma and primitive neuroectodermal tumor (MG-PNET) are rare, poorly characterized, and pose diagnostic as well as treatment dilemmas. We studied 53 MG-PNETs in patients from 12 to 80 years of age (median = 54 years). The PNET-like component consisted of sharply demarcated hypercellular nodules with evidence of neuronal differentiation. Anaplasia, as seen in medulloblastomas, was noted in 70%. Within the primitive element, N-myc or c-myc gene amplifications were seen in 43%. In contrast, glioma-associated alterations involved both components, 10q loss (50%) being most common. Therapy included radiation (78%), temozolomide (63%) and platinum-based chemotherapy (31%). Cerebrospinal fluid (CSF) dissemination developed in eight patients, with response to PNET-like therapy occurring in at least three. At last follow-up, 27 patients died, their median survival being 9.1 months. We conclude that the primitive component of the MG-PNET: (i) arises within a pre-existing MG, most often a secondary glioblastoma; (ii) may represent a metaplastic process or expansion of a tumor stem/progenitor cell clone; (iii) often shows histologic anaplasia and N-myc (or c-myc) amplification; (iv) has the capacity to seed the CSF; and (v) may respond to platinum-based chemotherapy regimens.

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.

Patterns of brain infiltration and secondary structure formation in supratentorial ependymal tumors

Ependymomas are generally considered to be noninfiltrative tumors that have discrete borders with adjacent brain tissue. Most occur in the posterior fossa or spinal cord. Supratentorial ependymal tumors arise near the ventricular system or, more rarely, within the cerebral white matter or cortex. Presented here are 6 supratentorial ependymal tumors, 3 that primarily involve the cerebral cortex and 3 that extend into the cortex from the underlying white matter. By microscopy, all of these tumors locally infiltrate the cortex and/or white matter along small blood vessels and axonal fiber tracts. They also form other glioma secondary structures including perineuronal tumor cell satellitosis and subpial tumor cell mounds. The 3 cortical ependymal tumors show a spectrum of features ranging from conventional and clear-cell ependymoma-like patterns to more angiocentric glioma-like histology. Because ependymal tumors generally have a significantly better prognosis than other infiltrating gliomas, recognition of their capacity to infiltrate adjacent cortex and white matter is important to prevent the misdiagnosis of oligodendroglioma, astrocytoma, or infiltrating glioma, not otherwise specified. Cortical ependymomas and angiocentric gliomas may comprise a group of locally infiltrative ependymal tumors that are associated with an excellent prognosis after gross total surgical resection.

Interphase cytogenetics for 1p19q and t(1;19)(q10;p10) may distinguish prognostically relevant subgroups in extraventricular neurocytoma

Co-deletion of chromosome arms 1p and 19q, characteristic of oligodendroglial tumors, was recently found to be mediated by t(1;19)(q10;p10). To evaluate the prevalence of 1p19q co-deletion and t(1;19) in extraventricular neurocytomas (EVN), we studied tumors from 23 patients, including 13 females and 10 males (median age at diagnosis 34 years, range 2-76 years). Fluorescence in situ hybridization (FISH) studies were performed with probes targeting 1p36/1q25 and 19q13/19p13 to assess for 1p19q co-deletion, as well as chromosome 1 alpha-satellite and 19p12 to detect t(1;19)(q10;p10). FISH was successful in 21 (91%) cases and demonstrated 1p19q co-deletion in five cases (24%) or isolated 1p loss in two cases (10%). Evidence for t(1;19) was found in four (of five) cases with 1p19q co-deletion. Three tumors with 1p19q loss and t(1;19) demonstrated atypical histologic features, compared with one (of 17) tumors without 1p19q co-deletion (P = 0.01, Fisher exact test). In addition, tumors with t(1;19) showed increased mitotic activity compared with tumors without t(1;19) (P = 0.045; Wilcoxon rank sum test). The four patients with t(1;19) developed tumor recurrence (n = 3), or expired (n = 2) 3.5 to 5.5 years after first resection. These results suggest that 1p19q loss and t(1;19) occur in a subset of EVN, and may be associated with aggressive histology in these tumors.

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.

Ependymal tumors with sarcomatous change ("ependymosarcoma"): a clinicopathologic and molecular cytogenetic study

Gliosarcomas are uncommon primary tumors of the central nervous system defined as exhibiting both glial and sarcomatous components. Sarcomatous change occurring in ependymal tumors is rare. We identified 11 such examples. There were 6 female and 5 male patients (median age, 18 y; range, 2 to 63). The tumors were located in the parieto-occipital (n=2), temporal (n=1), parietal (n=1), frontal (n=1), and occipital lobes (n=1), as well as the lateral ventricles (n=2), insula (n=1), cerebellopontine angle (n=1), and fourth ventricle/cerebellopontine angle (n=1). At presentation, the sarcomatous component was noted in 6 (of 10) cases and the ependymal element was grade III in 7 and grade II in 3 tumors, respectively. The sarcomatous component consisted of a reticulin rich, glial fibrillary acidic protein-negative fibrosarcoma (n=5) or pleomorphic spindle cell sarcoma (n=3), and 2 examples with heterologous elements: osseous and cartilaginous (n=1) and osseous only (n=1). The single case involving the fourth ventricle/left cerebellopontine angle consisted of subependymoma and fibrosarcoma components in roughly equal proportions at presentation. Fluorescence in situ hybridization studies performed with probes targeting the NF2 gene and other members of the protein 4.1 gene family demonstrated similar alterations in the ependymal and sarcomatous components in the cases tested, including polysomies/polyploidy (n=3), gains of 1q (n=3), deletions of 22q (n=2) and 6q (n=1), and monosomy 18 (n=1). There was no evidence of MDM2 or CCND1 amplification in any of the cases tested. On follow-up, 5 patients expired 4 months to 18 years after initial resection and 4 to 11 months after development of the sarcomatous component (mean, 7.6 mo); 1 patient is alive at 5 years with recurrent disease, and 1 is alive without recurrence 12 years after initial gross total resection followed by radiation therapy. Although rare, ependymal neoplasms must be included among the gliomas prone to undergo sarcomatous change and we propose the term "ependymosarcoma" for these tumors.

Ependymoma and intraparenchymal calcifying pseudoneoplasm of the neural axis: incidental collision or unique reactive phenomenon?

The so-called "calcifying pseudoneoplasm of the neural axis" is a rare tumefactive lesion presumed to be reactive in nature. To our knowledge, association with a true neoplasm has not been previously reported. We recently encountered the case of a 67-year-old woman who underwent resection of an incidentally discovered cerebellar cystic mass with a distinct, calcified component. Histology demonstrated a partially ossified, lobulated, chondrocalcific lesion surrounded by chronic inflammation, spindle to epithelioid cells, and occasional multinucleated giant cells-all features of calcifying pseudoneoplasm of the neural axis. A low-grade ependymoma associated with marked piloid gliosis was found contiguous to the lesion. The unique combination of an ependymoma with marked reactive gliosis and a calcifying pseudoneoplasm supports the reactive nature of the latter.

Choroid plexus papilloma with neuropil-like islands

Choroid plexus papilloma may display unusual histologic features, but the presence of neuronal differentiation at the light microscopic level has not yet been described. We thus report a choroid plexus papilloma with neuropil-like islands located within the lateral ventricle of an 11-year-old girl. The absence of atypical histologic features associated with recurrence (particularly increased mitotic activity) and recurrence-free follow-up upon gross total resection are compatible with a diagnosis of choroid plexus papilloma (WHO grade I). This case further emphasizes the capacity of choroid plexus tumor cells toward neuronal differentiation, and expands the spectrum of tumors, which may contain neuropil-like islands.

Neuronal differentiation and expression of neural epitopes in pituitary adenomas

Neural transdifferentiation is increasingly recognized in neural crest and neural stem cell tumors. Neuronal differentiation has been anecdotally described primarily in somatotroph cell adenomas associated with acromegaly, but its prevalence in adenomas and relationship to adenoma type has not been completely established. In this study we performed a retrospective morphological and immunohistochemical analysis of neurofilament, phosphoneurofilament, Neu-N, class III tubulin, and Hu in WHO grade I pituitary adenomas. Limited numbers of cells with neuronal features and neuron-associated epitopes may be more common in pituitary adenomas than previously recognized. These may occur in many forms of adenomas including somatotroph, lactotroph, mixed somatotroph and lactotroph, null cell/gonadotroph cell and, rarely, corticotroph cell adenomas.

Papillary tumor of the pineal region and spindle cell oncocytoma of the pituitary: new tumor entities in the 2007 WHO Classification

We have reviewed the features of two recently described intracranial tumors, which have been formally recognized as distinct entities by the 2007 WHO Classification of Brain Tumours: Papillary tumor of the pineal region and spindle cell oncocytoma of the pituitary gland. Their salient clinicopathological features, differential diagnosis, histogenetic hypothesis and outcome are discussed.