Figen Soylemezoglu

International Society of Neuropathology‐Haarlem Consensus Guidelines for Nervous System Tumor Classification and Grading

Major discoveries in the biology of nervous system tumors have raised the question of how non‐histological data such as molecular information can be incorporated into the next World Health Organization (WHO) classification of central nervous system tumors. To address this question, a meeting of neuropathologists with expertise in molecular diagnosis was held in Haarlem, the Netherlands, under the sponsorship of the International Society of Neuropathology (ISN). Prior to the meeting, participants solicited input from clinical colleagues in diverse neuro‐oncological specialties. The present “white paper” catalogs the recommendations of the meeting, at which a consensus was reached that incorporation of molecular information into the next WHO classification should follow a set of provided “ISN‐Haarlem” guidelines. Salient recommendations include that (i) diagnostic entities should be defined as narrowly as possible to optimize interobserver reproducibility, clinicopathological predictions and therapeutic planning; (ii) diagnoses should be “layered” with histologic classification, WHO grade and molecular information listed below an “integrated diagnosis”; (iii) determinations should be made for each tumor entity as to whether molecular information is required, suggested or not needed for its definition; (iv) some pediatric entities should be separated from their adult counterparts; (v) input for guiding decisions regarding tumor classification should be solicited from experts in complementary disciplines of neuro‐oncology; and (iv) entity‐specific molecular testing and reporting formats should be followed in diagnostic reports. It is hoped that these guidelines will facilitate the forthcoming update of the fourth edition of the WHO classification of central nervous system tumors.

Central Neurocytoma: A Synopsis of Clinical and Histological Features

The central neurocytoma is a supratentorial, often calcified brain tumour affecting young adults and is typically located in the lateral ventricles in the region of the foramen of Monro. Clinically, the tumour causes signs of increased intracranial pressure, visual and mental disturbances and, occasionally, pyramidal or endocrine symptoms. By light microscopy, the tumour is composed of small round cells in a delicate fibrillary matrix. Tumour cells consistently show features of neuronal differentiation by electron microscopy (synapses, dense‐core vesicles, presynaptic clear vesicles, specialized synaptic junctions) and immunoreactivity for synaptophysin and other neuronal marker proteins. The tumour can be totally removed in nearly half of the cases. After incomplete surgical resection neurocytomas may recur but because of their low proliferation potential, radio‐ or chemotherapy are not generally recommended. Postoperative recurrence‐free survival times of up to 19 years have been reported. Neurocytomas constitute nearly one half of supratentorial intraventricular tumours in adults but amount to less than 1% of all tumours of the central nervous system and its coverings.

Atypical central neurocytoma

The proliferative potential of central neurocytomas was determined in a biopsy series of 36 cases and compared with clinical outcome. The mean size of the growth fraction, as determined by MIB-1 labeling index (MIB-1 LI) at first biopsy, was 2.8 ± 2.5 with a range of 0.1 to 8.6%. Neurocytomas with an MIB-1 LI >2% comprised 39% of cases and showed a close correlation with the presence of vascular proliferation (p = 0.0006). The Kaplan-Meier analysis showed a highly significant difference in disease-free survival between the 2 groups (p =0.0068). Over an observation time of 150 months, there was a 22% relapse among patients with an MIB-1 LI less than 2% and a 63% chance of relapse among those with an MIB-1 LI greater than 2%. We propose the term “atypical central neurocytoma” for the latter subset, corresponding to WHO grade II.

Magnesium pre-treatment reduces neuronal apoptosis in newborn rats in hypoxia–ischemia

Hypoxic-ischemic brain damage has significant mortality and morbidity in newborns. Although the role of magnesium in neonatal hypoxic-ischemic brain injury related to N-methyl-D-aspartate receptors has been widely studied; the effects of magnesium on neuronal apoptosis have not been known exactly in hypoxia-ischemia. The aim of this study was to investigate the effects of magnesium on neuronal apoptosis in the 7-day-old rat hypoxia-ischemia model. Seven-day-old rats were administered magnesium sulfate (group 1; n=9) or saline (group 2; n=9) intraperitoneally before hypoxia-ischemia. Additionally 18 seven-day-old rats were given magnesium sulfate (group 3; n=9) or saline (group 4; n=9) after hypoxic-ischemic insult. Neuronal apoptosis was investigated by the dUDP-biotin nick end-labeling (TUNEL) method following 3-day recovery in all subjects. In evaluating TUNEL-positive cells, we firstly calculated the areas (mm(2)) of brain regions, hippocampus, striatum, cortex, in right and left hemispheres in subjects by IMAGE analysis. The numerical density was calculated as the number of cells per square millimeter by counting all TUNEL-positive cells. Afterwards, the ratio of right side numeric density to sum of right and left side numeric densities (right Apoptosis Index) was calculated for every brain region in rats receiving magnesium and compared to vehicle groups. The right Apoptosis Index of the hippocampus in magnesium pre-treated rats (mean+/-S.D.; 36.6+/-22.1) was significantly lower than vehicle (61.0+/-16.0; P<0.05); whereas right apoptosis indices were not changed by magnesium pre-treatment in striatum and cortex. Additionally, magnesium sulfate administration following hypoxic-ischemic insult also had no effect on right apoptosis indices in all three brain regions. It is concluded that magnesium might have a role in preventing neuronal apoptosis due to neonatal hypoxic-ischemic brain injury.

Nitric oxide is involved in ischemia-induced apoptosis in brain: a study in neuronal nitric oxide synthase null mice.

Nitric oxide can promote or inhibit apoptosis depending on the cell type and coexisting metabolic or experimental conditions. We examined the impact of nitric oxide on development of apoptosis 6, 24, and 72 h after permanent middle cerebral artery occlusion in mutant mice that lack the ability to generate nitric oxide from neuronal nitric oxide synthase. Adjacent coronal sections passing through the anterior commissure were stained with hematoxylin and eosin or terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). Immunoblotting was used to identify changes in the anti- and proapoptotic proteins Bcl-2 and Bax, respectively. Activation of caspases was assessed by appearance of actin cleavage products using a novel antiserum directed against 32-kDa actin fragment (fractin). In the neuronal nitric oxide synthase mutant mouse, infarct size and TUNEL positive apoptotic neurons were reduced compared to the wild-type controls. At 6 h, Bcl-2 levels in the ischemic hemisphere were increased in mutants but decreased in the wild-type strain. Bax levels did not change significantly. Caspase-mediated actin cleavage appeared in the ischemic hemisphere at this time point, and was significantly less in mutant brains at 72 h compared to the wild-type. The reduction in the number of TUNEL and fractin positive apoptotic cells appears far greater than anticipated based on the smaller lesion size in mutant mice.Hence, from these data we suggest that a deficiency in neuronal nitric oxide production slows the development of apoptotic cell death after ischemic injury and is associated with preserved Bcl-2 levels and delayed activation of effector caspases.

Neuronal nuclear antigen (NeuN): a new tool in the diagnosis of central neurocytoma.

The use of neuronal nuclear antigen (NeuN) as a reliable neuronal marker in the differential diagnosis of clear cell neoplasms of the central nervous system was determined in a biopsy series of 23 cases. Immunohistochemical analyses were carried out by antisera against neuronal nuclear antigen, synaptophysin, neuron-specific enolase, microtubule-associated protein 2, and glial fibrillary acidic protein. All eight central neurocytomas were characteristically immunolabeled by NeuN. NeuN immunoreactivity was uniformly strong and basically located in the nuclei of neurocytes. Despite this uniform staining pattern of central neurocytomas, 12 cases of oligodendrogliomas and three cases of ependymoma were negative for NeuN. As the diagnostic criteria for central neurocytoma include immunohistochemical and/or ultrastructural evidence for neuronal differentiation, NeuN as a sensitive and specific neuronal marker in formalin-fixed, paraffin-embedded tissues may greatly facilitate the differential diagnosis of central neurocytomas.

Is diffusion-weighted imaging useful in grading and differentiating histopathological subtypes of meningiomas?

PURPOSE Meningiomas are mostly benign, however atypical or malignant subtypes with more aggressive clinical course and higher recurrence rates can also be seen. The purpose of this study was to determine whether histopathological subtypes of meningiomas could be assessed preoperatively using apparent diffusion coefficient (ADC) values. MATERIALS AND METHODS Conventional magnetic resonance (MR) and diffusion-weighted (DW) imaging of 177 adult patients with pathologically proven meningiomas were retrospectively evaluated. Tumor size and the degree of associated edema were noted. The signal intensity of the lesions on DW imaging was evaluated and graded. Mean ADC values were obtained as the mean of measurements from three regions of interests within the mass. ADC ratios of meningioma/contralateral normal appearing subcortical parietal white matter were also calculated. RESULTS The histopathological analysis revealed 135 benign, 37 atypical and 5 malignant lesions. With classification according to the subtype, the mean ADC values and ratios of benign meningiomas were as 0.99±0.12×10(-3) mm(2)/s and 1.22±0.07, respectively. ADC values for atypical and malignant groups were both 0.84±0.1×10(-3) mm(2)/s. The ADC ratios were 1.05±0.1 and 0.96±0.2 for atypical and malignant subtypes, respectively. There was no statistically significant difference between the mean ADC ratios of the three subtypes (ANOVA test; P≥0.05). Gender, age of the patients and tumor size showed no statistically significant difference between the different histological groups. CONCLUSION DW MR imaging was not found to have any additional value in determining histological behaviour nor in differentiating histopathological subtypes of meningiomas.

Genetic and expression profiles of cerebellar liponeurocytomas

Cerebellar liponeurocytoma, a rare, newly identified CNS neoplasm of adults, is characterized by advanced neuronal/neurocytic and focal lipomatous differentiation, low proliferative potential and a favorable clinical prognosis. Despite the different age distribution and benign biological behavior, the cerebellar liponeurocytoma shares several features with the cerebellar medulloblastoma, which may include an origin from the periventricular matrix of the fourth ventricle or the external granular layer of the cerebellum. To establish the genetic profile of cerebellar liponeurocytomas, we have formed an international consortium and collected tumor samples from 20 patients. DNA sequencing revealed TP53 missense mutations in 4 (20%) of 20 cerebellar liponeurocytomas, a frequency higher than in medulloblastomas. There was no case with PTCH, APC, or β‐catenin mutations, each of which may be present in subsets of medulloblastomas. Isochromosome 17q, a genetic hallmark of classic medulloblastomas, was not observed in any of the cases investigated by FISH analysis. cDNA array analyses were carried out on 4 cerebellar liponeurocytomas, 4 central neurocytomas, and 4 classic medulloblastomas. Cluster analysis of the cDNA expression data of 1176 genes grouped cerebellar liponeurocytomas close to central neurocytomas, but distinct from medulloblastomas. These results suggest cerebellar liponeurocytoma as a distinct tumor entity that is genetically different from medulloblastoma. Furthermore, the cDNA expression array data suggest a relationship to central neurocytomas, but the presence of TP53 mutations, which are absent in central neurocytomas, suggests that their genetic pathways are different.

Investigation of HSV-1, HSV-2, CMV, HHV-6 and HHV-8 DNA by real-time PCR in surgical resection materials of epilepsy patients with mesial temporal lobe sclerosis

OBJECTIVE The objective of this study is to investigate the presence of viral DNAs of HSV-1, HSV-2, HHV-6, HHV-8, and CMV in hippocampus of the patients with mesial temporal lobe epilepsy (MTLE) syndrome. METHODS Pathological specimens were obtained from 33 patients with MTLE undergone temporal lobectomy with amygdalo-hippocampectomy due to intractable seizures. Autopsy materials from the hippocampus of 7 patients without neurological disease were used as controls. The data was also correlated with the clinical history of patients including febrile convulsions, age, and history of CNS infections. Real-time polymerase chain reaction method was performed for detection of DNAs of these viruses. RESULTS HHV-6, HSV-1 and HHV-8 were detected in the hippocampus of 3, 2 and 1 patients with MTLE respectively. None of the hippocampus of patients with MTLE was positive for DNA of HSV-2 and/or CMV. Three patients with positive HHV-6 DNAs had febrile convulsions and family history for epilepsy. None of our control specimens showed PCR positivity to any of the 5 tested viruses. CONCLUSIONS Our study is the first to report the presence of HHV-8 viral genome in the brain tissue of patient with MTLE. Viral DNAs were detected in a total of 18% of the patients in this study; we can conclude that activity of the latent virus in patients with hippocampal sclerosis should be more extensively studied to establish its role in active infection.

Serial analysis of gene expression in the hippocampus of patients with mesial temporal lobe epilepsy

Hippocampal sclerosis constitutes the most frequent neuropathological finding in patients with medically intractable mesial temporal lobe epilepsy. Serial analysis of gene expression was used to get a global view of the gene profile in human hippocampus in control condition and in epileptic condition associated with hippocampal sclerosis. Libraries were generated from control hippocampus, obtained by rapid autopsy, and from hippocampal surgical specimens of patients with mesial temporal lobe epilepsy and the classical pattern of hippocampal sclerosis. More than 50,000 tags were analyzed (28,282, control hippocampus; 25,953, hippocampal sclerosis) resulting in 9206 (control hippocampus) and 9599 (hippocampal sclerosis) unique tags (genes), each representing a specific mRNA transcript. Comparison of the two libraries resulted in the identification of 143 transcripts that were differentially expressed. These genes belong to a variety of functional classes, including basic metabolism, transcription regulation, protein synthesis and degradation, signal transduction, structural proteins, regeneration and synaptic plasticity and genes of unknown identity of function. The database generated by this study provides an extensive inventory of genes expressed in human control hippocampus, identifies new high-abundant genes associated with altered hippocampal morphology in patients with mesial temporal lobe epilepsy and serves as a reference for future studies aimed at detecting hippocampal transcriptional responses under various pathological conditions.