Transcriptional features of low-grade neuroepithelial tumors with the BRAF V600E mutation associated with epileptogenicity

Low-grade neuroepithelial tumors are major causes of drug-resistant focal epilepsy. Clinically, these tumors are defined as low-grade epilepsy-associated neuroepithelial tumors (LEATs). The BRAF V600E mutation is frequently observed in LEAT and linked to poor seizure outcomes. However, its molecular role in epileptogenicity remains elusive. To understand the molecular mechanism underlying the epileptogenicity in LEAT with the BRAF V600E genetic mutation (BRAF V600E-LEAT), we conducted RNA sequencing (RNA-seq) analysis using surgical specimens of BRAF V600E-LEAT obtained and stored at a single institute. We obtained 21 BRAF V600E-LEAT specimens and 4 control specimens, including 24 from Japanese patients and 1 from a patient of Central Asian origin, along with comprehensive clinical data. We submitted the transcriptome dataset of 21 BRAF V600E-LEAT plus 4 controls, as well as detailed clinical information, to a public database. Preliminary bioinformatics analysis using this dataset identified 2134 differentially expressed genes between BRAF V600E-LEAT and control. Additionally, gene set enrichment analysis provided novel insights into the association between estrogen response-related pathways and the epileptogenicity of BRAF V600E-LEAT patients. Our datasets and findings will contribute toward the understanding of the pathology of epilepsy caused by LEAT and the identification of new therapeutic targets.

Dysembryoplastic neuroepithelial tumors: A single-institutional series with special reference to glutamine synthetase expression

Dysembryoplastic neuroepithelial tumors (DNT) is a benign (World Health Organisation, WHO, grade I) glioneuronal tumor and it represent one of the most frequent neoplasm in patient affected by seizures. The epileptic neuronal activity can be determined by abnormal synchronization, excessive glutamate excitation and\or inadequate GABA inhibition. Increasing evidence suggests that the astrocytes might be involved in this process even if neurons play a relevant role. In particular astrocytes promote the clearance of glutamate, a potent excitatory neurotransmitter of the central nervous system. Indeed, elevated concentrations of extracellular glutamate may determine iper-excitability and seizures as well as other neurological disorders. So, astrocytes, converting glutamate into glutamine via the enzyme glutamine synthetase (GS), could play a protective anti-seizures role. In the present study, we analyzed the immunohistochemical expression of GS in 20 DNTs specimens documenting a constant immunoistochemical expression of GS in astrocytes of the lesional tissue and of the cerebral cortex.

Relationship among clinical, pathological and bio-molecular features in low-grade epilepsy-associated neuroepithelial tumors

The aim of this study was to evaluate the relationship between molecular markers and clinicopathological features in patients operated on for low-grade epilepsy-associated neuroepithelial tumors. Molecular-genetic signatures are becoming increasingly important in characterizing these lesions, which represent the second most common cause of focal epilepsy in patients undergoing epilepsy surgery. Data from 22 patients operated on for histopathologically confirmed low-grade epilepsy-associated neuroepithelial tumors were retrospectively collected. All specimens were examined for BRAF and IDH mutational status, 1p/19q codeletion and CD34 expression. The relationship between bio-molecular markers and several demographic, clinical and pathological features were analyzed. BRAF mutation was found in 11 (50.0%) patients and CD34 expression in 13 (59.1%). No patients presented IDH mutation or 1p/19q codeletion. Multiple seizure types were present in 5 (45.5%) patients with BRAF mutation and in none of those with BRAF wild type (p=0.035). Moreover, BRAF mutation was predominant in right-sided lesions (p=0.004) and CD34 expression was significantly associated with a longer duration of epilepsy (p=0.027). Several other clinicopathological features, such as association with focal cortical dysplasia and postoperative seizure outcome, showed no significant correlation with molecular markers. Further studies are necessary both to confirm these data in larger cohort of patients and to investigate possible relationships between molecular markers and other clinicopathological features.

Gliomatosis cerebri in children shares molecular characteristics with other pediatric gliomas

Gliomatosis cerebri (GC), a rare and deadly CNS neoplasm characterized by involvement of at least three cerebral lobes, predominantly affects adults. While a few small series have reported its occurrence in children, little is known about the molecular characteristics of pediatric GC. We reviewed clinical, radiological, and histological features of pediatric patients with primary GC treated at our institution over 15 years. Targeted sequencing of mutational hotspots in H3F3A, IDH1/2, and BRAF, and genome-wide analysis of DNA methylation and copy number abnormalities was performed in available tumors. Thirty-two patients [23 (72 %) with type 1 and 9 (28 %) with type 2 GC] were identified. Median age at diagnosis was 10.2 years (range 1.5-19.1). A median of 4 cerebral lobes (range 3-8) was affected at diagnosis. In addition, symmetrical bithalamic involvement was observed in 9 (28 %) patients. Twenty-two patients (69 %) had an anaplastic astrocytoma. Despite aggressive therapy, only two patients younger than 3 years at diagnosis are long-term survivors. Clustering analysis of methylation array data from 18 cases classified tumors as IDH (n = 3, 17 %), G34 (n = 4, 22 %), mesenchymal (n = 3, 17 %), and RTK I 'PDGFRA' (n = 8, 44 %). No tumors were classified as K27 subgroup. PDGFRA was the most commonly amplified oncogene in 4 of 22 tumors (18 %). H3F3A p.G34 occurred in all cases classified as G34. Two of 3 cases in the IDH subgroup had IDH1 p.R132H. No H3F3A p.K27 M, IDH2 p.R172, or BRAF p.V600E mutations were observed. There was a trend towards improved survival in the IDH subgroup (P = 0.056). Patients with bithalamic involvement had worse outcomes (P = 0.019). Despite some overlap, the molecular features of pediatric GC are distinct from its adult counterpart. Like in adults, the similarity of genetic and epigenetic characteristics with other infiltrative high-grade gliomas suggests that pediatric GC does not represent a distinct molecular entity.

Evidence for involvement of steroid receptors and coactivators in neuroepithelial and meningothelial tumors

Steroid receptors such as androgen receptor (AR) and estrogen receptors (ER) ER-α and ER-β, and their receptor coactivators (steroid receptor coactivator, SRC) are widely localized in the brain. Although previous studies have investigated the expression of steroid receptors in brain tumors like astrocytoma, the studies on the expression of steroid receptors and SRCs in other brain tumors are lacking. Here, we investigated the expression of AR, ERs, and SRCs in neuroepithelial (medulloblastoma, ependymoma, oligodendroglioma) and meningothelial meningioma using tissue microarray immunohistochemistry. Compared to normal brain tissue, we found that the expression of SRC-1, SRC-3, and ER-α significantly decreased in meningothelial tumor and neuroepithelial tumor, suggesting that the SRC-1/SRC-3 levels may be regulated by ER-α. Moreover, the levels of AR strongly correlated to the levels of ER-β. Furthermore, correlation was also detected between SRC-3 and AR in neuroepithelial tumor, and between ER-α and ER-β in meningothelial tumor. In addition, the decreased ratio of SRC-1/SRC-3 was associated with an increase of ER-β in neuroepithelial tumor. These results indicate that expressions of different steroid receptors and activators may be tumor type dependent. While AR, ER-α, and ER-β may be involved in the pathogenesis of meningothelial tumor, SRCs/ER-β axis and SRC-3/AR axis may play a role in the pathogenesis of neuroepithelial tumor.

Cathepsin D and its prognostic value in neuroepithelial brain tumors

Expression of Cathepsin D (Cath D) in some primary neuroepithelial brain tumors and its prognostic value were studied. The research included 65 samples of human primary neuroepithelial brain tumors. There were 50 glial tumors (10 diffuse astrocytomas (DA), 15 anaplastic astrocytomas (AA), 25 glioblastomas (GB), 15 embryonic tumors (15 medulloblastomas (MB) as well as 5 samples of normal brain tissue. Immunohistochemical method was applied to monitor diffuse positive reaction in the cytoplasm of brain tumor cells, endothelial cells and tumor stromal cells and showed diffuse positive reaction for Cath D in the cytoplasm of brain tumor cells, endothelial cells and stromal cells in all analyzed samples of DA, AA, GB and MB as well as in microglial cells, neurons and in endothelial cells in all analyzed samples of normal brain tissue. Qualitative analysis of Cath D expression in the cytoplasm of brain tumor cells and endothelial cells as well as the percentage of brain tumor cells, endothelial cells and stromal cells immunopositive for Cath D showed that there was difference between analyzed brain tumor groups, but according to statistical tests the difference was not statistically significant. Survival correlated with the percentage of stromal cells immunopositive for Cath D. Survival prognosis was influenced by the percentage of stromal cells immunopositive for Cath D and tumor grade. The obtained results singled out the percentage of stromal cells immunopositive for Cath D as an independent parameter. The results of this research on the prognostic value of Cath D in some primary brain tumors of neuroepithelial origin indicate that there is real possibility to use Cath D as an independent prognostic factor in human glioma progression and thus open up possibilities for further scientific research.

GLUT1 expression in malignant tumors and its use as an immunodiagnostic marker

OBJECTIVE

To analyze glucose transporter 1 expression patterns in malignant tumors of various cell types and evaluate their diagnostic value by immunohistochemistry.

INTRODUCTION

Glucose is the major source of energy for cells, and glucose transporter 1 is the most common glucose transporter in humans. Glucose transporter 1 is aberrantly expressed in several tumor types. Studies have implicated glucose transporter 1 expression as a prognostic and diagnostic marker in tumors, primarily in conjunction with positron emission tomography scan data.

METHODS

Immunohistochemistry for glucose transporter 1 was performed in tissue microarray slides, comprising 1955 samples of malignant neoplasm from different cell types.

RESULTS

Sarcomas, lymphomas, melanomas and hepatoblastomas did not express glucose transporter 1. Forty-seven per cent of prostate adenocarcinomas were positive, as were 29% of thyroid, 10% of gastric and 5% of breast adenocarcinomas. Thirty-six per cent of squamous cell carcinomas of the head and neck were positive, as were 42% of uterine cervix squamous cell carcinomas. Glioblastomas and retinoblastomas showed membranous glucose transporter 1 staining in 18.6% and 9.4% of all cases, respectively. Squamous cell carcinomas displayed membranous expression, whereas adenocarcinomas showed cytoplasmic glucose transporter 1 expression.

CONCLUSION

Glucose transporter 1 showed variable expression in various tumor types. Its absence in sarcomas, melanomas, hepatoblastomas and lymphomas suggests that other glucose transporters mediate the glycolytic pathway in these tumors. The data suggest that glucose transporter 1 is a valuable immunohistochemical marker that can be used to identify patients for evaluation by positron emission tomography scan. The function of cytoplasmic glucose transporter 1 in adenocarcinomas must be further examined.

[Expression and diagnostic significance of CD34 in brain tumors of patients with refractory epilepsy]

OBJECTIVE

To study the immunohistochemical expression and diagnostic significance of CD34 in brain tumors of patients with refractory epilepsy.

METHODS

Immunohistochemical study for CD34 was performed on formalin-fixed paraffin-embedded tissue blocks of 54 cases of brain tumors occurring in patients with refractory epilepsy. The tumor types included ganglioglioma (GG, number = 21), dysembryoplastic neuroepithelial tumor (DNT, number = 8), tumors/lesions which had the transitional features that between glioneuronal hamartia and mixed neuronal-glial tumor (number = 21) and pleomorphic xanthoastrocytoma (PXA, number = 4). Cases of glioblastoma (number = 4) and oligoastrocytoma (number = 5) were used as controls.

RESULTS

Twenty of the 21 cases of GG, 1 of the 8 cases of DNT, 16 of the 21 cases of tumors/lesions which had the transitional features and 3 of the 4 cases of PXA showed cytoplasmic and membranous positivity for CD34. The adjoining brain tissues in 9 of the 18 cases of GG, 6 of the 16 cases of tumors/lesions which had the transitional features and 1 of the 3 cases of PXA also expressed CD34. In contrast, only 1 case of glioblastoma showed membranous positivity for CD34.

CONCLUSIONS

CD34 preferred to staining for GG and PXA. Which represent a valuable tool for distinguishing GG, PXA and DNT, oligoastrocytoma, glioblastoma.

Multifocal dysembryoplastic neuroepithelial tumor with signs of atypia after regrowth

We report the case of a multifocal dysembryoplastic neuroepithelial tumor (DNT) in a 7-year-old girl with local tumor regrowth 6 years later. The tumor was localized in the right parietal lobe extending from the cortex into the periventricular white matter. After subtotal resection of a histopathologically confirmed DNT we observed unexpected tumor progression in long-term follow-up. Therefore, a second surgery was performed when the patient was 14 years of age. In neuropathological examination of the second specimen the tumor showed an increased cellularity and pleomorphism, microvascular proliferations, an elevated proliferative activity (MIB1-index focally up to 10%) and cellular atypia not typical for WHO grade I DNT. Furthermore, MRI studies showed additional supratentorial and infratentorial lesions which remained stable over years and are also well consistent with DNTs. Thus, an unusual form of a DNT with multifocal lesions, local regrowth and morphological transformation is supposed.

[Dysembryoplastic neuroepithelial tumor: a clinicopathologic and immunohistochemical study]

OBJECTIVE

To study the clinicopathologic features, immunophenotype and histogenesis of dysembryoplastic neuroepithelial tumor (DNT).

METHODS

Fourteen cases of DNT were retrieved from the archival files of the Department. The histopathologic features and immunohistochemical findings were retrospectively studied. The long-term follow-up data were analyzed.

RESULTS

Eleven of the 14 cases studied were located in the temporal lobe. Histologically, the tumor consisted of a heterogeneous admixture of neuronal and glial cells (including 1 simple form case, 8 complex form cases and 5 non-specific form cases). The specific glioneuronal element was seen in 9 cases. Variable degrees of cortical dysplasia (CD) were found in 10 out of the 11 cases which had sufficient tissue samples for thorough histologic examination. The morphologic appearance of CD included the presence of heterotopic neurons in molecular layer and/or white matter (7 cases), persistent subpial granular cell layer (4 cases), dyslamination (10 cases) and cellular abnormalities. Immunohistochemically, the oligodendroglial-like cells expressed Olig2. Some of which were positive for nestin, MAP-2, neurofilament and glial fibrillary acidic protein, but negative for NeuN. Long-term follow up revealed that 12 patients had class I postoperative seizure and 2 patients had class II seizure. No tumor recurrence was detected.

CONCLUSIONS

DNT is frequently associated with CD. The morphologic diagnosis can be confirmed by immunohistochemical study using a panel of antibodies.

OLIG2 is a useful immunohistochemical marker in differential diagnosis of clear cell primary CNS neoplasms

AIMS

To analyse OLIG2 expression in clear cell primary central nervous system (CNS) tumours to clarify the diagnostic usefulness of OLIG2 immunohistochemistry in this subset of brain tumours.

METHODS AND RESULTS

We analysed OLIG2 expression in 60 oligodendroglial neoplasms (57 with and three without chromosome 1p aberration), 10 central neurocytomas, 10 clear cell ependymomas, nine dysembryoplastic neuroepithelial tumours (DNTs) and two clear cell meningiomas using immunohistochemistry. Additionally, we analysed oligodendroglial neoplasms with numerous gliofibrillary and minigemistocytic oligodendrocytes for OLIG2/glial fibrillary acidic protein (GFAP) coexpression and central neurocytoma for coexpression of neurone-specific nuclear protein (NeuN) and OLIG2 using double immunofluorescent labelling and confocal laser scanning microscopy. All oligodendroglial neoplasms and DNTs showed widespread OLIG2 expression. Eight of 10 central neurocytomas, all clear cell meningiomas and 8/10 clear cell ependymomas were negative for OLIG2. Two of 10 central neurocytomas and 2/10 clear cell ependymomas showed focal OLIG2 expression. We found prominent coexpression of GFAP and OLIG2 in gliofibrillary and minigemistocytic oligodendrocytes. Further, we found coexpression of NeuN and OLIG2 in single cells in central neurocytoma.

CONCLUSIONS

Widespread OLIG2 expression discriminates oligodendroglial neoplasms or DNTs from other clear cell primary brain tumour types. In clear cell primary brain tumours lacking OLIG2 expression, differential diagnosis may require additional immunohistochemical markers.

The clinical value of proton magnetic resonance spectroscopy in adult brain tumours

Proton magnetic resonance spectroscopy (1H MRS) non-invasively provides information on the biochemical profile (typically including up to nine metabolites and mobile lipids) of brain tissue, which varies according to the underlying disease process. A number of studies have assessed its accuracy in the diagnosis of adult brain tumours. This article describes the basic principles of 1H MRS, the metabolic profiles of different brain tumours, and practical points to aid interpretation of spectra. The literature is reviewed regarding the role of 1H MRS in the diagnosis of brain tumours and more specifically where it has proven to be of additional benefit over conventional magnetic resonance imaging.

Clinical features and epileptogenesis of dysembryoplastic neuroepithelial tumor

INTRODUCTION

Dysembryoplastic neuroepithelial tumor (DNT) frequently causes medically intractable epilepsy.

OBJECTIVE

The aim of this study was to investigate the basic mechanism of epileptogenecity of the tumor.

MATERIALS AND METHODS

Clinicopathological data in 13 cases of DNT and immunohistochemical changes of ionotropic glutamate receptor subunits in the tumor and peritumoral epileptogenic cortex were studied.

CONCLUSIONS

Magnetic resonance imaging combined with electroencephalography (EEG), electrocorticography, and depth-electrode EEG was valuable to localize complicated epileptogenic zones of the patients with DNT. Neuropathological examinations of the peritumoral cerebral cortex presenting abnormal spikes showed different histopathological grades of neuronal migration disorder (NMD). The tumor cells in DNT disclosed increased immunopositivities of N-methyl-D: -aspartate receptor 1 (NR1) and NR2A/B, and peritumoral epileptogenic NMD revealed increased immunopositivities of GluR2 and GluR3. The amplification of ionotropic glutamate receptor subunits in the tumor and peritumoral NMD may be the underlying cause of epileptic seizures in DNT patients.

Evaluation of molecular genetic alterations associated with tumor progression in a case of gliomatosis cerebri

Gliomatosis cerebri (GC) is a rare tumor characterized by widespread infiltration of the brain and spinal cord. Although GC usually demonstrates histomorphological features of a low-grade tumor, the formation of secondary highly malignant tumor regions may occur. In order to reveal molecular genetic changes associated with tumor progression in GC, we analyzed factors known to be associated with malignant progression in common astocytomas in an unusual GC case of an 18-year-old patient suffering from this disease for almost 7 years. We detected allelic losses in the Rb gene and in exon 4 of the TP53 gene in a tumor region corresponding to a glioblastoma multiforme. EGFR or MDM2 gene amplifications were absent, and no PTEN mutation or allelic loss on chromosome 10 could be detected. Moreover, compared to tumor-free brain tissue of this patient, tumor regions showed increased EGFR expression. These findings show that malignant progression in GC might be associated with the acquisition of molecular genetic changes also found in low-grade astrocytomas with progression to secondary glioblastoma. These data support the notion that GC can be regarded as a subtype of a common astrocytoma.

[The role of matrix metalloproteinases and tissue inhibitors of metalloproteinases in invasion of tumours of neuroepithelial tissue]

Tumour invasion requires degradation of extracellular matrix components and migration of cells through degraded structures into surrounding tissues. Matrix metalloproteinases (MMP) constitute a family of zinc and calcium-dependent endopeptidases that play a key role in the breakdown of extracellular matrix, and in processing of cytokines, growth factors, chemokines and cell surface receptors. Their activity is regulated at the levels of transcription, activation and inhibition by tissue inhibitors of metalloproteinases (TIMP). Changes in expression of MMP and TIMP are implicated in tumour invasion, because they may contribute to both migration of tumour cells and angiogenesis. Alterations of MMP expression observed in brain tumours arouse interest in the development and evaluation of synthetic matrix metalloproteinase inhibitors as antitumour agents.

Expression of SOX9 and SOX10 in central neuroepithelial tumor

The SOX group E transcription factors play an integral role in the specification and differentiation of astrocytes and oligodendrocytes. We have examined the pattern of expression for SOX9 and SOX10 in primary brain tumors by immunohistochemistry. Pediatric and adult high grade tumors display strong nuclear staining for both SOX9 and SOX10 (astrocytic, oligodendroglial and primitive neuroectodermal tumors). In comparison pediatric pilocytic astrocytoma express much less SOX9 and SOX10. Reactive astrogliosis is characterized by an increase of SOX9 only.

Astroblastoma: immunohistochemical and ultrastructural study of distinctive epithelial and probable tanycytic differentiation

We report the clinicopathological findings of astroblastoma found in an 8-year-old girl who was subsequently treated for 11 years. The primary superficially circumscribed tumor was located in the frontoparietal lobe, while the recurrent and the second recurrent tumor were restricted to the same region 11 years later. The tumors obtained on these three occasions showed fundamentally the same histological, immunohistochemical and fine structural features. They exhibited astrocytic as well as ependymal tanycytic features with apparent epithelial cell lineage. The tumor cells showed typical features of astroblastoma comprising prominent perivascular pseudorosettes with remarkable vascular sclerosis. The immunohistochemical study revealed intensive positivity of GFAP, vimentin, epithelial membrane antigen (EMA), cytokeratin, connexin 26 and 32, desmocollin 1 and neuronal cadherin. The fine structure revealed divergent types of junctional complexes, some of which were connected with tonofilament bundles. Numerous microvilli protruded and basal lamina abutted on the tumor cell surface. We report these unique histological features, and stress that astroblastoma should be categorized as a specific type of neuroepithelial tumor.

Nestin expression in neuroepithelial tumors

Nestin is a marker of early stages of neurocytogenesis. It has been studied in 50 neuroepithelial tumors, mostly gliomas of different malignancy grades, by immunohistochemistry, immunofluorescence, immunoblotting, and confocal microscopy and compared with GFAP and Vimentin. As an early marker of differentiation, Nestin is almost not expressed in diffuse astrocytomas, variably expressed in anaplastic astrocytomas and strongly and irregularly expressed in glioblastomas. Negative in oligodendrogliomas, it stains ependymomas and shows a gradient of expression in pilocytic astrocytomas. In glioblastomas, Nestin distribution does not completely correspond to that of GFAP and Vimentin with which its expression varies in tumor cells in a complementary way, as confirmed by confocal microscopy. Tumor cells can thus either derive from or differentiate toward the neurocytogenetic stages. Hypothetically, they could be put in relation with radial glia where during embriogenesis the three antigens are successively expressed. Completely negative cells of invasive or recurrent glioblastomas may represent malignant selected clones after accumulation of mutations or early stem cells not expressing antigens.

Magnetic resonance spectroscopy: a noninvasive diagnosis of gliomatosis cerebri

Gliomatosis cerebri (GC) is characterized by a diffuse infiltration of neoplastic glial cells with preservation of neuronal architecture. It can be very difficult to diagnose during life because the clinical manifestations are protean and tests are often nondiagnostic. The diagnosis of GC needs to be based on radiological, clinical and pathological criteria. We present a patient with GC, which initially presented as acute stroke attack. We discuss the usefulness of noninvasive methods, such a MR spectroscopy, in the diagnosis, grading and management of GC.

Development of contrast enhancement after long-term observation of a dysembryoplastic neuroepithelial tumor

Dysembryoplastic neuroepithelial tumors (DNET) are usually benign lesions that arise in cortical regions and are discovered after new onset of seizure. These lesions have many different imaging characteristics. We report a patient with a presumed low-grade medial temporal lobe lesion that was followed for many years without any change in size or imaging characteristics. This previously non-enhancing tumor evolved to become contrast enhanced on routine imaging without apparent tumor growth. The patient underwent surgery, and the pathology was confirmed as a DNET with no atypical changes. This case demonstrates the potential that DNETs may exhibit a changing MRI pattern over time. Natural history, imaging characteristics, and management are reviewed.

[A clinicopathologic study of dysembryoplstic neuroepithelial tumor]

OBJECTIVE To study the clinicopathologic features, radiologic findings, treatment modalities and prognosis of dysembryoplastic neuroepithelial tumor (DNT).

METHODS

The clinical features, histopathologic findings, immunohistochemistry and electron microscopy of 18 cases of DNT were analyzed. Results Among the 18 cases studied, 14 were males and 4 females. The age of these patients ranged from 3 to 46 (mean age = 22. 8 years). Partial seizure was the main presenting symptom in all patients. The history of epilepsy could be as long as 17 years. On magnetic resonance imaging (MRI) study, the tumor was hypodense on T1 and hyperdense on T2. There was neither edema nor mass effect. All but 2 cases were supratentorial and intracortical in location. Ten cases were treated by complete surgical excision and the remaining 8 tumors were partially excised. In the 14 patients with follow-up data available, 13 survived for 1.4 to 11 years after the operation (with more than 10 years survival observed in 2 patients). The average survival period was 5.5 years. None of the cases showed tumor recurrence after operation. Histologically, all tumors demonstrated a multinodular architecture and were intracortical in location, sometimes with extension into the white matter. The characteristic "glioneuronal constituent" was an essential feature for making the diagnosis of DNT. The tumor was formed by an admixture of oligodendrocyte-like cells, mature neurons and astrocytes, with obvious microcystic changes. These neurons were often dispersed singly in the mucoid matrix. In most cases, the foci of cortical dysplasia were found in adjacent areas. Immunohistochemical study demonstrated positivity for synaptophysin, neurofilament and S-100 protein in the neurons and some oligodendrocyte-like cells. The staining of glial fibrillary acidic protein in the oligodendrocyte-like cells was negative. Electron microscopy showed early neuronal, astrocytic and oligodendroglial differentiation of the oligodendrocyte-like cells.

CONCLUSIONS

DNT is a benign tumor (corresponding to WHO grade I) that can be cured by surgical excision, despite sometimes incomplete tumor removal. A correct diagnosis of this entity requires thorough understanding of the clinical, radiologic, histologic and immunohistochemical features.

Gliomatosis Cerebri and Pituitary Adenoma: Case Report and Literature Review

The diagnosis of Gliomatosis cerebri (GC) is known to be difficult and is still a matter of debate. We describe an in vivo case of GC associated with a pituitary tumor. A 47-year-old woman presented with short-term memory loss. A MRI revealed the presence of a pituitary enhancing tumor and a diffuse lesion involving the brain. A left pterional craniotomy with partial temporal lobectomy and removal of the pituitary lesion were performed in order to obtain diagnosis. The histological analyses showed a pituitary non-functioning tumor and a GC consisting of neoplastic oligodendrocytes and astrocytes. Both lesions showed nuclear immunoreactivity for progesterone receptors (PGr) and estrogen receptors (EGr). This result could suggest there is a common receptor substrate in these tumors. In this case hormones could constitute a common step in tumorigenesis of both lesions.

Genetic evidence for a tumor suppressor role of HIF-2alpha

The hypoxia-inducible transcription factors HIF-1alpha and HIF-2alpha are activated in hypoxic tumor regions. However, their role in tumorigenesis remains controversial, as tumor growth promoter and suppressor activities have been ascribed to HIF-1alpha, while the role of HIF-2alpha remains largely unknown. Here, we show that overexpression of HIF-2alpha in rat glioma tumors enhances angiogenesis but reduces growth of these tumors, in part by increasing tumor cell apoptosis. Moreover, siRNA knockdown of HIF-2alpha reduced apoptosis in hypoxic human malignant glioblastoma cells. Furthermore, inhibition of HIF by overexpression of a dominant-negative HIF transgene in glioma cells or HIF-2alpha deficiency in teratomas reduced vascularization but accelerated growth of these tumor types. These findings urge careful consideration of using HIF inhibitors as cancer therapeutic strategies.

Assessment of tumor cell invasion factors in gliomatosis cerebri

Gliomatosis cerebri (GC) is a rare brain tumor characterized by widespread infiltration of large parts of the brain and sometimes even the spinal cord. To determine the cause of this extraordinary degree of brain invasion, we studied immunoexpression of factors associated with brain infiltration in low-grade and high-grade tumor samples from nine GC cases. We further determined the allelic status of the fibroblastic growth factor receptor 4 (FGFR4) gene at position 388 (arginine [Arg(388)] or glycine [Gly(388)]) in eighteen GC patients, because the presence of at least one Arg(388) allele has been suggested to favor tumor cell motility compared to tumor cells homozygeous for the Gly(388) allele. Immunohistochemical analyses showed that tumor samples from three GC cases expressed Tenascin-C, whereas six cases had CD44 - immunopositive tumor samples. Expression of MMP-9 was not observed in any of the nine GC patients. FGFR4 genotyping revealed the presence of the Arg(388) in 72% of the eighteen GC cases, a frequency similar to the one found in 21 common astrocytomas (71%). In tumor-free control DNA, the Arg(388) phenotype was present in 60%. These data indicate that CD44 expression might be related to the tumor infiltration in GC, and that patients suffering from GC or other common astrocytomas do not have a significantly increased frequency of the tumor cell motility-favoring Arg(388) FGFR4 allele.

Differential expression of delta-like gene and protein in neuroblastoma, ganglioneuroblastoma and ganglioneuroma

Neuroblastoma is an extremely malignant solid tumor in children, characterized by spontaneous differentiation and regression. An epidermal growth factor-like homeotic protein, delta-like (dlk), has been involved in differentiation of neuroblastoma cell lines, but is unknown in in vivo expression of neuroblastoma. By using in situ hybridization and immunohistochemistry, dlk mRNA and protein expression were studied in formalin-fixed archival tissues from 10 patients with neuroblastoma, five with ganglioneuroblastoma, and five with ganglioneuroma. Three adrenal tissues from children died of diseases other than adrenal tumors and one from an adult with pheochromocytoma were severed as normal and disease controls. The results showed strong immunoreactive dlk staining in endothelial cells in neuroblastoma, ganglioneuroblastoma and ganglioneuroma. Dlk was detectable in mature neuromatous stroma and gangliocytes of ganglioneuroma, but not in neuroblasts of neuroblastoma and ganglioneuroblastoma, neither in gangliocytes of ganglioneuroblastoma. In contrast, dlk mRNA expression was mainly observed in the gangliocytes, but was less intense in the neuroblasts and neuromatous stroma cells. Endothelial cells were essentially devoid of dlk mRNA expression. The findings indicated that there is differential expression of dlk gene and protein among neuroblastoma, ganglioneuroblastoma and ganglioneuroma. The stronger expression of dlk in gangliocytes in ganglioneuroma, in contrast to weaker or no expression in gangliocytes in ganglioneuroblastoma and neuroblasts in neuroblastoma, suggests upregulation of dlk during differentiation of neuroblastoma into more benign form. Furthermore, higher dlk protein expression in the tumor endothelium than in the endothelium of normal adrenal gland implies that dlk may regulate the endothelial function in neuroblastic tumors.

Alterations of cell cycle regulators in gliomatosis cerebri

Gliomatosis cerebri (GC) is regarded as a rare glial neoplasm of unknown origin, and a detailed analysis of molecular alterations underlying this disease has started only recently. However, because GC characteristically affects large parts of the brain and spinal cord, the distribution of genetic alterations may be highly variable between different tumor areas. Additionally, tumor areas with varying degrees of differentiation may be present, raising the possibility to model the genetic events associated with astrocytoma progression. Here we analyzed various tumor regions with features of low-grade and high-grade astrocytomas from 9 autopsy-proven GC cases for the immunoexpression of the cell cycle-controlling proteins mdm2, p21, p27/kip1, p16, and Rb. The samples were also screened for EGFR expression, and for amplification of the EGFR and MDM2 genes. Furthermore, allelic losses of the CDKN2A gene and of a PTEN flanking region of chromosome 10 were determined. We detected tumor regions with immunoexpression of p21 only rarely in our series, without association to the tumor grade. No MDM2 gene amplification was detected. In contrast, three cases demonstrated maintained Rb expression. The expression of p27(kip1) showed a clear reduction with increasing astrocytoma malignancy in 7 cases. Allelic loss of the CDKN2A gene occurred in 5 patients but was not related to the tumor grading, nor to the intensity of p16 immunoexpression. No homozygous CDKN2Adeletions were detected. EGFR amplification was also absent in our series, but one case demonstrated EGFR expression only in the high-grade tumor area. Allelic losses on chromosome 10 were found in one out of six informative cases. However, marked differences in the immunoexpression, as well as in the distribution of genetic aberrations were seen between different tumor samples within a given case. The distribution of the alterations suggests that these molecular genetic changes represent secondary events, which may develop within tumor clones derived from a common founder tumor clone characterized by extraordinary spreading through the brain. Moreover, the detected aberrations in gliomatosis cerebri can reflect the tumor progression associated with secondary malignant astrocytoma formation even within a single case.

Astroblastoma: a case report

Astroblastoma is one of the very unusual type of tumors, whose histogenesis has not been clarified. It occurs mainly among children or young adults. Astroblastoma is grossly well-demarcated, and shows histologically characteristic perivascular pseudorosettes with frequent vascular hyalinization. Perivascular pseudorosettes in astroblastoma have short and thick cytoplasmic processes and blunt-ended foot plates. A 15-yr-old girl presented with headache and diplopia for one and a half year. A well-demarcated mass, 9.7 cm in diameter, was found in the right frontal lobe in brain MRI, and it was a well-enhanced inhomogenous mass. Cystic changes of various sizes were observed inside the tumor mass as well as in the posterior part of the mass, but no peritumoral edema was found. Histologically, this mass belongs to a typical astroblastoma, and no sign of anaplastic astrocytoma, gemistocytic astrocytoma or glioblastoma was found in any part of the tumor. Immunohistochemically, the tumor cells showed diffuse strong positivity for glial fibrillary acidic protein, S-100 protein, vimentin and neuron specific enolase, and focal positivity for epithelial membrane antigen and CAM 5.2, while showing negativity for synaptophysin, neurofilament protein, pan-cytokeratin and high molecular weight keratin.

Papillary neuroepithelial tumor of the pineal region. A case report

We present here an unusual case of papillary neuroepithelial tumor of the pineal region. The patient was a 29-year-old female who presented with headaches. A computed tomography scan revealed a tumorous lesion at the pineal region and hydrocephalus. The resected tumor was composed of columnar and cuboidal cells showing characteristics of papillary growth. The tumor cells exhibited diffuse and intense immunoreactivity to cytokeratins and neural cell adhesion molecule. The tumor expressed abundant levels of transthyretin (prealbumin) and appeared ependymal in nature, with numerous microlumens delineated by punctate and ring-like patterns in epithelial membrane antigen staining. Reactivity to synaptophysin and glial fibrillary acidic protein was observed only in the infiltrated non-neoplastic pineal parenchyma. These histological characteristics matched the description of the recently reported papillary tumor of the pineal region thought to originate from the specialized ependyma of the subcommissural organ (SCO). Transthyretin expression of the present case further supports the likelihood of SCO origin, as transthyretin is one of the proteins presumed to be secreted by human SCO.

Expression of multidrug transporters in dysembryoplastic neuroepithelial tumors causing intractable epilepsy

OBJECTIVE

Dysembryoplastic neuroepithelial tumors (DNT) are relatively benign brain lesions that often cause medically intractable epilepsy. There is mounting evidence that multidrug transporters such as P-glycoprotein (P-gp) or multidrug resistance-associated proteins (MRP) play an important role in the development of resistance to antiepileptic drugs (AED).

MATERIAL AND METHODS

In the present study, we examined the expression of several multidrug transporters in 14 cases of DNT. The peritumoral brain tissue as well as 9 cases of arteriovenous malformations (AVM) served as controls. P-gp, MRP2, MRP5 and breast cancer resistance protein (BCRP) expression was evaluated qualitatively and quantitatively using immunohistochemistry.

RESULTS

All transporters were overexpressed quantitatively in DNT, but each revealed a different labeling pattern. P-gp and BCRP were predominantly located in the endothelium of brain vessels. MRP5 was detected primarily in endothelial cells, but notably also in neurons. The expression of P-gp, MRP2 and MRP5 was low in AVM, whereas BCRP demonstrated strong staining. Examination of MDR1 gene polymorphisms revealed no correlation with P-gp expression whereas the MRP2 exon 10 G1249A polymorphism was associated with different MRP2 labelling.

CONCLUSIONS

Our results show that multidrug transporters are overexpressed in DNT. This finding supports the view that several of these transport proteins may play an important role in the mechanisms of drug resistance in epileptic brain tissue.

Microtubule-associated protein-2 immunoreactivity: a useful tool in the differential diagnosis of low-grade neuroepithelial tumors

Complex and variable morphological phenotypes pose a major challenge to the histopathological classification of neuroepithelial tumors. This applies in particular for low-grade gliomas and glio-neuronal tumors. Recently, we and others have identified microtubule-associated protein-2 (MAP2) as an immunohistochemical marker expressed in the majority of glial tumors. Characteristic cell morphologies can be recognized by MAP2 immunoreactivity in different glioma entities, i.e., process sparse oligodendroglial versus densely ramified astrocytic elements. Here, we describe MAP2-immunoreactivity patterns in a large series of various neuroepithelial tumors and related neoplasms (n = 960). Immunohistochemical analysis led to the following conclusions: (1) specific pattern of MAP2-positive tumor cells can be identified in 95% of glial neoplasms; (2) ependymal tumors do not express MAP2 in their rosette-forming cell component; (3) tumors of the pineal gland as well as malignant embryonic tumors are also characterized by abundant MAP2 immunoreactivity; (4) virtually no MAP2 expression can be observed in the neoplastic glial component of glio-neuronal tumors, i.e. gangliogliomas; (5) malignant glial tumor variants (WHO grade III or IV) exhibit different and less specific MAP2 staining patterns compared to their benign counterparts (WHO grade I or II); (6) with the exception of melanomas and small cell lung cancers, MAP2 expression is very rare in metastatic and non-neuroepithelial tumors; (7) glial MAP2 expression was not detected in 56 non-neoplastic lesions. These data point towards MAP2 as valuable diagnostic tool for pattern recognition and differential diagnosis of low-grade neuroepithelial tumors.

Usefulness of [11C]Methionine PET in the Diagnosis of Dysembryoplastic Neuroepithelial Tumor with Temporal Lobe Epilepsy

PURPOSE

We assessed the diagnostic value of [11C]methionine (MET) positron emission tomography (PET) in the differential diagnosis of dysembryoplastic neuroepithelial tumors (DNETs) among benign tumors associated with temporal lobe epilepsy (TLE).

METHODS

This series consisted of seven TLE patients with benign tumors in the temporal lobe. After MET-PET study, all seven patients underwent tumor resection along with focus excision. The uptake of tracers was evaluated by the lesion-to-contralateral ratio (L/C ratio) and the standardized uptake value (SUV). We also assessed the relation between MET uptake and proliferation capacity observed in the surgical specimens.

RESULTS

Whereas four patients with DNETs did not show high MET uptake visually, the ganglioglioma and gliomas of the remaining three patients were identified as high-MET-uptake lesions. In the DNETs, the SUV ranged from 1.03 to 1.41, and the L/C ratio ranged from 0.99 to 1.14. MET uptake was significantly lower in the patients with DNETs than in the patients with ganglioglioma and brain gliomas (SUV, p = 0.045; L/C ratio, p = 0.0079). The Ki-67 labeling index was 4% in one patient with DNET and 5% in one patient with pleomorphic xanthoastrocytoma (higher labeling index). The higher labeling index was not related to high MET uptake based on the SUV (p = 0.91) and L/C ratio (p = 0.38).

CONCLUSIONS

Negative MET uptake in benign temporal lobe tumors with TLE is consistent with a preoperative diagnosis of DNET.

Malignant transformation of a dysembryoplastic neuroepithelial tumor after radiation and chemotherapy

We describe a case of anaplastic astrocytoma in a 14-year-old boy arising at the site of a dysembryoplastic neuroepithelial tumor (DNT) 3 years after combined radiation and chemotherapy. The subtotally excised superficial right temporoparietal tumor was originally diagnosed as mixed oligoastrocytoma in 1974; the patient was treated with radiation therapy postoperatively. One year later he underwent a craniotomy to remove cyst fluid and no change was reported in the size of the residual tumor. Postoperatively, he received a 6-week course of chemotherapy (lovustine, CCNU). He remained clinically and radiographically stable until 3 years later, when seizure activity returned and imaging studies were consistent with tumor recurrence. He was lost to follow-up until 1986, when records showed that he had died. Review of the initial biopsy showed cortical fragments containing abundant calcifications and multinodular structures typical of the complex form of DNT, in addition to specific glioneuronal elements. The Ki-67 labeling index ranged from 0.1% to 3% focally. The specimen from the third surgery showed an anaplastic astrocytoma (Ki-67 up to 12%) and morphologic features characteristic of radiation effect. This is the first documented case of malignant transformation of DNT following radiation and adjuvant chemotherapy. The implications of malignant transformation in subtotally excised complex DNTs and the intriguing issue of the contribution of radiation/chemotherapy are discussed.

Analysis of TP53 and PTEN in gliomatosis cerebri

Gliomatosis cerebri (GC) is a rare glial neoplasm with extensive diffuse brain infiltration but relative preservation of the underlying architecture. Previous molecular studies, mostly analyzing biopsy samples, have suggested an astrocytic origin of GC, but a larger collective of autopsy tissue has not been investigated so far. Furthermore, whether the widespread neoplastic infiltration is based on a monoclonal process is still a matter of debate. In the present study, we screened paraffin-embedded brain tissue from different areas of 18 cases (8 autopsy cases and 10 biopsies) for alterations in the TP53 and PTEN genes. Nuclear accumulation of p53 protein was detected in 9 cases (50%). Somatic TP53 mutations occurred in two autopsy cases (11% of all cases). In the first case, a C-->T transition in codon 273 (Arg-->Cys) was detected in all tumor samples. In the second case, in tumor samples from one hemisphere, nuclear accumulation of p53 was caused by a G-->A transition in codon 244 (Gly-->Asp). In the present series, no mutations within the coding region of PTEN were found. Pten expression was observed in two autopsy cases (25%) and seven biopsy samples (70%). These data suggest that TP53 is affected in some cases, but other yet-unidentified genetic alterations might contribute to tumorigenesis in GC. Furthermore, although GC might be a monoclonal process, the presence of different tumor clones cannot be ruled out.

Use of proton magnetic resonance spectroscopy of the brain to differentiate gliomatosis cerebri from low-grade glioma

OBJECT

Gliomatosis cerebri (GC), a rare entity characterized by a widespread infiltration of brain by tumor, lacks objective and quantitative diagnostic criteria. Single-voxel spectroscopy and chemical shift imaging (two-dimensional proton magnetic resonance [MR] spectroscopy) were performed using both short (20- or 22-msec) and long (135-msec) echo times in nine patients suffering from GC, nine patients with low-grade gliomas (LGGs), and 25 healthy volunteers to establish the precise metabolic pattern of this uncommon brain neoplasm.

METHODS

The gliomatosis infiltration was characterized by markedly elevated levels of creatine-phosphocreatine (Cr) and mvo-inositol (Ins), a reduced level of N-acetyl aspartate (NAA), and a moderately elevated level of choline-containing compounds (Cho). This pattern differs strikingly from LGGs, which are characterized by elevated levels of Cho and Ins, markedly reduced levels of NAA, and low-to-normal Cr concentrations. Although the distinction between GC and LGG, based on histological and MR imaging criteria, is a matter of debate, MR spectroscopy produces valuable information for the differentiation between these two entities and, hence, the choice of therapeutic strategy. It also provides new insight into the pathophysiology of GC because elevated Cr and Ins levels may be related to proliferation of glial elements or, more probably, activation of normal glia. Elevated levels of Cho reflect cellular proliferation and reduced NAA corresponds to reversible neuronal injury and/or focal invasion by the tumor process.

CONCLUSIONS

Owing to the unfavorable clinical outcome associated with GC compared with that associated with LGG, the findings of this study illustrate the diagnostic and prognostic value of proton MR spectroscopy in the characterization of infiltrating gliomas.

Distribution of p53 alterations in a case of gliomatosis cerebri

Gliomatosis cerebri (GC) is a rare neuroepithelial tumor characterized by diffuse infiltration of large parts of the brain. The origin of GC is unknown, and the molecular alterations underlying this tumor have not been determined. Because mutations in the p53 tumor-suppressor gene are frequent in common gliomas, we investigated the distribution of p53 alterations by immunohistochemistry and direct sequencing in a GC case with a disease involving both hemispheres and the basal ganglia. Nuclear accumulation of p53 protein was detected in a single region with features of a high-grade glioma. In the remaining 10 regions, corresponding to low-grade gliomas, no p53 accumulation was seen. In 1 low-grade tumor sample, a pathogenic splice site mutation was detected. These findings suggest that p53 alterations occur in GC, but are no prerequisite of malignant progression. The distribution of p53 alterations demonstrates the existence of topographically different clones in 1 patient.

Increased choline levels coincide with enhanced proliferative activity of human neuroepithelial brain tumors

Proton MR spectroscopy ((1)H MRS)-visible total choline-containing compounds (tCho-compounds) are derivatives of membrane phospholipids and, in part, may act as a long-term second-messenger system for cellular proliferation. Experimental evidence suggests increasing concentrations of tCho-compounds during cellular proliferation. The present study was conducted in order to test the hypothesis that in vivo measurements of tCho-concentrations using (1)H MRS allow assessment of the proliferative activity of neuroepithelial brain tumors presurgically. Single-voxel (1)H MRS (PRESS, TR 1500 ms, TE 135 ms) was performed in 101 patients with neuroepithelial brain tumors prior to surgery and 19 healthy volunteers. Histological diagnoses were confirmed postsurgically according to the WHO classification. Measured tCho-compound signal intensities were corrected for coil loading, numbers of acquisitions and voxel size, and tCho concentrations calculated as institutional arbitrary units. They were matched with the mean immunohistochemical marker of cell proliferation, the Ki-67 (MIB.1) labeling index, using correlation analysis according to Spearman. Compared with low-grade tumors (i.e. WHO grade I/II) and normal white brain matter, high-grade tumors (i.e. WHO grade III/IV) revealed significantly (p < 0.05) elevated labeling indices paralleled by increasingly elevated tCho-concentrations. In contrast tCho-concentrations in low-grade tumor did not differ significantly from physiological values. A highly significant positive correlation (p < 0.0001, r(2) = 0.81) was found between the tCho-concentration and the labeling index. It was concluded that the determination of tCho-concentrations using in vivo (1)H MRS could provide a novel and noninvasive assessment of the proliferative activity of neuroepithelial brain tumors, pointing at (1)H MRS as a useful method for differentiating proliferating from non-proliferating tissues. Hence, potential indications for the clinical application of (1)H MRS are grading tumors presurgically, early detection of anaplastic transformation, and monitoring treatment.

CD9 expression in solid non-neuroepithelial tumors and infiltrative astrocytic tumors

The tetraspan membrane protein CD9 is normally expressed in the mature myelin sheath and is believed to suppress the metastatic potential of certain human tumors. In this study we identified CD9 in a variety of brain tumors by immunohistochemical (IHC) and immunoblotting analyses. We examined 96 tumor samples and three glioma cell lines in addition to a murine brain tumor model of transplanted glioma cells in CD9-deficient mice and control mice. CD9 was expressed not only in solid non-neuroepithelial tumors but also in infiltrative malignant neuroepithelial tumors. Among the neuroepithelial tumors, high-grade astrocytic tumors, including glioblastomas and anaplastic astrocytomas, showed higher immunoreactivity than low-grade cerebral astrocytomas. Thus, CD9 expression in astrocytic tumors correlated with their malignancy. In the murine brain tumor model, transplanted glioma cells were shown to grow and spread through myelinated areas irrespective of the presence or absence of CD9 expression in the recipient's brain. These results indicate that the CD9 expression of astrocytic tumors plays a significant role in the malignancy independent of CD9 expression in the surrounding tissue. This might be explained by the observation that the CD9 molecule is associated with a mitogenic factor, membrane-anchored heparin-binding epidermal growth factor, which is known to be upregulated in malignant gliomas.

Astroblastoma with unusual signet-ring-like cell components: a case report and literature review

We report a case of astroblastoma with unusual signet-ring-like cell components. A 33-year-old-woman presented with occasional partial seizures of the face. Radiological studies revealed an enhanced frontal mass lesion. At surgery, a gray, soft, well-circumscribed mass was seen and shelled out. Histologically, the tumor showed a perivascular arrangement and papillary-like patterns with compact cellularity. The tumor cells radiating from the hyalinized vessels showed broader, shorter, less tapered processes. A part of each tumor cell displayed prominent islands of signet-ring-like cells. Glial fibrillary acidic protein reaction revealed strongly positive staining of tumor cells and signet-ring-like cells. Eight years after the operation the patient remains well with no tumor recurrence. It remains to be determined whether, in this astroblastoma, the unusual signet-ring-like cell components were related to benign biological characteristics or to the tumor's low-grade form with incidental signet-ring-like cell appearance.

Dysembryoplastic neuroepithelial tumour (DNT). Is the mechanism of seizures related to glutamate? An immunohistochemical study

Dysembryoplastic neuroepithelial tumour (DNT) is a rare low-grade, mixed neuronal and glial tumour, usually associated with pharmacologically intractable, complex partial or generalised seizures which date from childhood. The prognosis after surgery is favourable. We present a classic case of DNT occurring in an 18-year-old male, who presented simple partial seizures without signs of raised intracranial pressure. CT and MR demonstrated focal mass located in the right temporal lobe. Histologically there were found the features of a typical DNT architecture with mixed cellular composition. The response to surgery was excellent. The tumour has not recurred, and the control of seizures remained good. Immunostaining for glutamate receptor GluR-2 showed stronger immunopositivity in neurones dispersed within the tumour and especially in margins of lesion as compared with apparently normal cerebral cortex. The expression of both excitatoryamino acid transporterproteins EAAT1 and EAAT2 was weaker then in normal cortex and uneven. This perhaps may explain the mechanism of seizures (elevated glutaminergic stimulation), and may suggest the excitotoxic damage of neurones.

Drug resistance in epilepsy: expression of drug resistance proteins in common causes of refractory epilepsy

Epilepsy is resistant to drug treatment in about one-third of cases, but the mechanisms underlying this drug resistance are not understood. In cancer, drug resistance has been studied extensively. Amongst the various resistance mechanisms, overexpression of drug resistance proteins, such as multi-drug resistance gene-1 P-glycoprotein (MDR1) and multidrug resistance-associated protein 1 (MRP1), has been shown to correlate with cellular resistance to anticancer drugs. Previous studies in human epilepsy have shown that MDR1 and MRP1 may also be overexpressed in brain tissue from patients with refractory epilepsy; expression has been shown in glia and neurones, which do not normally express these proteins. We examined expression of MDR1 and MRP1 in refractory epilepsy from three common causes, dysembryoplastic neuroepithelial tumours (DNTs; eight cases), focal cortical dysplasia (FCD; 14 cases) and hippocampal sclerosis (HS; eight cases). Expression was studied immunohistochemically in lesional tissue from therapeutic resections and compared with expression in histologically normal adjacent tissue. With the most sensitive antibodies, in all eight DNT cases, reactive astrocytes within tumour nodules expressed MDR1 and MRP1. In five of eight HS cases, reactive astrocytes within the gliotic hippocampus expressed MDR1 and MRP1. Of 14 cases of FCD, MDR1 and MRP1 expression was noted in reactive astrocytes in all cases. In five FCD cases, MRP1 expression was also noted in dysplastic neurones. In FCD and DNTs, accentuation of reactivity was noted around lesional vessels. Immunoreactivity was always more frequent and intense in lesional reactive astrocytes than in glial fibrillary acidic protein-positive reactive astrocytes in adjacent histologically normal tissue. MDR1 is able to transport some antiepileptic drugs (AEDs), and MRP1 may also do so. The overexpression of these drug resistance proteins in tissue from patients with refractory epilepsy suggests one possible mechanism for drug resistance in patients with these pathologies. We propose that overexpressed resistance proteins lower the interstitial concentration of AEDs in the vicinity of the epileptogenic pathology and thereby render the epilepsy caused by these pathologies resistant to treatment with AEDs.

Distinct expression pattern of microtubule-associated protein-2 in human oligodendrogliomas and glial precursor cells

Microtubule-associated protein 2 (MAP2), a protein linked to the neuronal cytoskeleton in the mature central nervous system (CNS), has recently been identified in glial precursors indicating a potential role during glial development. In the present study, we systematically analyzed the expression of MAP2 in a series of 237 human neuroepithelial tumors including paraffin-embedded specimens and tumor tissue microarrays from oligodendrogliomas, mixed gliomas, astrocytomas, glioblastomas, ependymomas, as well as dysembryoplastic neuroepithelial tumors (DNT), and central neurocytomas. In addition, MAP2-immunoreactive precursor cells were studied in the developing human brain. Three monoclonal antibodies generated against MAP2A-B or MAP2A-D isoforms were used. Variable immunoreactivity for MAP2 could be observed in all gliomas with the exception of ependymomas. Oligodendrogliomas exhibited a consistently strong and distinct pattern of expression characterized by perinuclear cytoplasmic staining without significant process labeling. Tumor cells with immunoreactive bi- or multi-polar processes were mostly encountered in astroglial neoplasms, whereas the small cell component in neurocytomas and DNT was not labeled. These features render MAP2 immunoreactivity a helpful diagnostic tool for the distinction of oligodendrogliomas and other neuroepithelial neoplasms. RT-PCR, Western blot analysis, and in situ hybridization confirmed the expression of MAP2A-C (including the novel MAP2+ 13 transcript) in both oligodendrogliomas and astrocytomas. Double fluorescent laser scanning microscopy showed that GFAP and MAP2 labeled different tumor cell populations. In embryonic human brains, MAP2-immunoreactive glial precursor cells were identified within the subventricular or intermediate zones. These precursors exhibit morphology closely resembling the immunolabeled neoplastic cells observed in glial tumors. Our findings demonstrate MAP2 expression in astrocytic and oligodendroglial neoplasms. The distinct pattern of immunoreactivity in oligodendrogliomas may be useful as a diagnostic tool. Since MAP2 expression occurs transiently in migrating immature glial cells, our findings are in line with an assumed origin of diffuse gliomas from glial precursors.

Gliomatosis cerebri: post-mortem molecular and immunohistochemical analyses in a case treated with thalidomide

Gliomatosis cerebri (GC) is a rare tumor of the central nervous system (CNS) characterized by widespread diffuse infiltration of the brain and spinal cord by neoplastic glial cells. We report the case of a 17-year-old boy with a bioptically diagnosed fibrillary astrocytoma. The administration of thalidomide, which was suggested to be beneficial in the treatment of human cancers, had no substantial clinical effect on our patient. Autopsy studies revealed a diffuse infiltration of the frontal and temporal lobes of the right hemisphere, brainstem, and the leptomeninges covering the whole spinal cord by an astrocytic tumor, which showed features both of low-grade astrocytoma and glioblastoma multiforme. No mutations in the p53 and PTEN tumor suppressor genes were found; immunoreactivities for p53, PTEN, and EGFR could not be detected.

The bacterial nucleoside N(6)-methyldeoxyadenosine induces the differentiation of mammalian tumor cells

Contrary to bacterial DNA, mammalian DNA contains very little if any N(6)-methyldeoxyadenosine (MDA). The possible biological effect of this nucleoside on eukaryotic cells has been studied on different tumor cell lines. Addition of MDA to C6.9 glioma cells triggers a differentiation process and the expression of the oligodendroglial marker 2',3'-cyclic nucleotide 3'phosphorylase (CNP). The biological effects of N(6)-methyldeoxyadenosine were not restricted to C6.9 glioma cells since differentiation was also observed on pheochromocytoma and teratocarcinoma cell lines and on dysembryoplastic neuroepithelial tumor cells. The precise mechanism by which MDA induces cell differentiation remains unclear, but is related to cell cycle modifications. These data point out the potential interest of N(6)-methyldeoxyadenosine as a novel antitumoral and differentiation agent. They also raise the intriguing question of the loss of adenine methylation in mammalian DNA. Furthermore, the finding that a methylated nucleoside found in bacterial DNA induces a biological process might have implications in gene therapy approaches when plasmid DNAs are injected into humans.

Ionotropic and metabotropic glutamate receptor protein expression in glioneuronal tumours from patients with intractable epilepsy

Glioneuronal tumours are an increasingly recognized cause of chronic pharmaco-resistant epilepsy. In the present study the immunocytochemical expression of various glutamate receptor (GluR) subtypes was investigated in 41 gangliogliomas (GG) and 16 dysembryoplastic neuroepithelial tumours (DNT) from patients with intractable epilepsy. Immunocytochemistry with antibodies specific for ionotropic NR1, NR2A/B (NMDA) GluR1, GluR2 (AMPA), GluR5-7 (kainate), and metabotropic mGluR1, mGluR2-3, mGluR5, mGluR7a subtypes demonstrated in both GG and DNT the presence of an highly differentiated neuronal population, containing subunits from each receptor class. More than 50% of tumours contained a high percentage of neuronal cells immunolabelled for NMDA, AMPA and kainate receptor subunits. A high percentage of neurones showed strong expression of NR2A-B, which co-localized with NR1. Group I mGluRs (mGluR1 and mGluR5) were highly represented in the neuronal component of the tumours. Immunolabelling for several GluRs was also present in the glial component. Increased expression of mGluR2-3, mGluR5 and GluR5-7 was observed in reactive astrocytes in the perilesional zone compared to normal cortex. The neurochemical profile of glioneuronal tumours, with high expression of specific GluR subtypes, supports the central role of glutamatergic transmission in the mechanisms underlying the intrinsic and high epileptogenicity of these lesions.

A case of an unclassified tumor closely resembling dysembryoplastic neuroepithelial tumor with rapid growth

We describe a rare case of a tumor resembling dysembryoplastic neuroepithelial tumor. A 3-year-old girl had a generalized convulsion as the initial symptom, without other neurological deficits. Computed tomography showed a hypodense lesion with calcific hyperdensity in the left frontal lobe associated with deformity of the overlying calvarium. Four months later, she had a second seizure, and computed tomographic scan showed that the lesion had increased in size. Subtotal removal of the tumor was performed, and the postoperative course was uneventful without radiation therapy. Histological examination revealed a cortical lesion in which an oligodendrocyte-like area and an astrocyte-like area with cytological atypia were observed. Although the clinical course and the radiological findings closely resembled those of dysembryoplastic neuroepithelial tumor, specific glioneuronal elements were not found histologically. Daumas-Duport reported a complex form of dysembryoplastic neuroepithelial tumor that contained glial nodules in addition to a specific glioneuronal element. The histological findings of the glial nodules in this case were quite similar to those she described. We conclude that this could be an unclassified tumor closely resembling dysembryoplastic neuroepithelial tumor without a specific glioneuronal element.

Hsp70 plasma membrane expression on primary tumor biopsy material and bone marrow of leukemic patients

A tumor-selective cell surface localization of heat shock protein 70 (Hsp70), the major heat-inducible member of the Hsp70 group, correlates with an increased sensitivity to lysis mediated by human natural killer (NK) cells and, therefore, might be of clinical relevance. With the exception of mammary carcinomas, an Hsp70 plasma membrane expression was found on freshly isolated human biopsy material of colorectal, lung, neuronal, and pancreas carcinomas, liver metastases, and leukemic blasts of patients with acute myelogenous leukemia. Since normal tissues and bone marrow of healthy human individuals do not express Hsp70 on the cell surface, Hsp70 can be considered as a tumor-selective structure in vivo. Furthermore, we demonstrate that autologous, Hsp70-positive leukemic blasts can be killed by NK cells stimulated with low doses of interleukin 2 plus recombinant Hsp70 protein.

Histological heterogeneity of dysembryoplastic neuroepithelial tumour: identification and differential diagnosis in a series of 74 cases

AIMS

In a retrospective study of resected specimens from 416 patients being treated for long-standing epilepsy, 74 cases of dysembryoplastic neuroepithelial tumour (DNT) were encountered that were all characteristically composed of small round oligodendroglia-like cells (OLC), astrocytes and mature neurones in varying proportions. The architectural patterns, histological, immunohistochemical and ultrastructural features and results of cell proliferation studies and postoperative follow-up are described to facilitate the identification of DNT and to differentiate it from other intrinsic neoplasms that commonly present with seizures.

METHODS AND RESULTS

The tumours presented with early onset of seizures, at a median age of 7 years, without the signs of raised intracranial pressure. A majority of the lesions were located in the temporal lobe (n = 59), with fewer cases in the frontal (n = 8), parietal (n = 6) and occipital lobes (n = 1), and ranged in size from 10 to 70 mm; 33 were cystic. Histologically three types could be distinguished, multinodular, solitary nodular and diffuse. The first type (37.8%) had the features of a typical DNT with multinodular architecture and mixed cellular composition. The second type (33.8%) consisted of a solitary nodule, while the third (28.4%) was a diffuse tumour, both composed of a similar mixture of cells as the multinodular DNT. The lesions were seen in the neocortex and white matter and tumours in the temporal lobe often involved the amygdala and hippocampus. The presence of myxoid matrix, microcystic change, calcification and leptomeningeal involvement were common. Dysplastic neurones at the periphery of the tumour and abnormalities in cortical lamination in the adjacent neocortex were found in about one-third of the resections. Rare mitotic figures were encountered in eight of the tumours and necrosis was found in two. Immunocytochemistry for glial fibrillary acidic protein (GFAP) and neuronal markers neuron-specific enolase, synaptophysin and neurofilament (RT 97) assists in establishing the diagnosis, highlighting the astrocytic and neuronal components, and the OLC, by the absence of expression of GFAP. Electron microscopy showed that in some cases OLC show neuronal differentiation. Although the proliferating cell nuclear antigen labelling index varied between 0 and 45.5%, 20 of the 51 tumours stained failed to express the antigen, in keeping with the indolent nature of this neoplasm. The response to surgery was excellent; none of the tumours have recurred, and the control of seizures remained good.

CONCLUSIONS

Despite some histological heterogeneity, the clinical and pathological features and indolent biological behaviour indicate that these tumours constitute a single distinct entity. The spectrum of morphological appearances of DNT is broader than has been previously reported, the recognition of which is needed to avoid unnecessary neoadjuvant therapy.