Central neurocytoma: establishment of the disease entity.

The establishment and identification of central neurocytoma as a distinct disease entity are invaluable in catalyzing investigations of neuronal differentiation in central nervous system tumors. The discovery of neuronal differentiation in neuroepithelial tumors has been extended to extraventricular tumors and potentially to various glial tumors undergoing neuronal differentiation. Understanding the disease spectrum of neuronal and mixed neuronal-glial tumors is important for deciphering the mechanism of gliomagenesis.

Atypical and rare variants of central neurocytomas.

This article reviews the variation in imaging, histopathology, clinical course, and management seen with central neurocytomas (CNs). CNs have often been misdiagnosed as oligodendrogliomas and ependymomas; however, synaptophysin positivity can correctly diagnose these neurocytic neoplasms. Atypical CNs, an important variant first described in 1997, are marked by increased proliferative potential and associated with worse clinical outcomes in terms of long-term survival and local tumor control. Complete surgical resection is the cornerstone of therapy, and postoperative radiation is recommended in the setting of residual disease. Other less aggressive variants of central neurocytomas, including liponeurocytomas, ganglioneurocytomas, and pigmented neurocytomas, are also discussed.

Atypical extraventricular neurocytoma:A report of two cases.

Central neurocytomas are tumors with neuronal differentiation, generally arising in the lateral ventricles in the region of foramen of Monro. Whenever these tumors arise in the brain parenchyma they are called "extraventricular neurocytomas". We present two unusual cases of extraventricular atypical neurocytomas at uncommon locations with a very high Ki-67 index. The WHO grading of this tumor is yet to be answered.

MRI findings in patients with central neurocytomas with special reference to differential diagnosis from other ventricular tumours near the foramen of Monro.

We retrospectively evaluated 12 patients with histologically verified central neurocytoma (CN) to identify the MRI characteristics associated with this tumour. All tumours had heterogeneous signal intensity in their solid components and seven had a "soap bubble" or spongy appearance. Spicules were identified at the tumour periphery interfacing with the lateral ventricular walls. These spicules were formed by walls of multiple cysts of medium size. Undulation of the lateral ventricular wall attached to the tumour capsule was seen in nine patients. These spicules and undulations resulted in a "scalloping" appearance. In a diagnostic experiment to test the differential diagnosis of CN from other neoplasms near the foramen of Monro, the identification of scalloping made a greater contribution to the specificity and accuracy of the diagnosis than the soap bubble appearance. Thus, recognition of multiple cystic interfaces between the solid part of the tumour and the lateral ventricular wall on MRI may contribute to a correct preoperative diagnosis of CN.

2007 World Health Organization classification of tumours of the central nervous system.

This article presents a brief review of the 2007 World Health Organization classification of tumours of the central nervous system.

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 beta-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.

Atypical extraventricular neurocytoma with oligodendroglioma-like spread and an unusual pattern of chromosome 1p and 19q loss.

An insular cortex tumor in a 54-year-old woman showed unequivocal neurocytic features, including open nuclei, distinct nucleoli, and strong synaptophysin immunoreactivity. Ultrastructurally, there were neuritic-type processes with microtubules and hillock-like attachments, and there were dense-core granules. Atypical features were mitotic activity, prominent vasculature, and small foci of necrosis. Peripherally, there was oligodendroglia-like histology with single-cell infiltration of white matter and perineuronal spread in cortex. Fluorescence in situ hybridization analysis with chromosome 1 and 19 probes showed 3 copies of 1q and 2 copies of 1p and showed 2 copies of 19q and 4 copies of 19p. This yielded a 1p-19q loss of heterozygosity pattern similar to that seen in oligodendrogliomas, although the actual chromosomal abnormality is distinct. This tumor, best classified as an atypical neurocytoma with oligodendroglia-like spread, supports suggestions of a close histogenic relationship between oligodendroglial and neurocytic tumors. This case also illustrates the limitations of relying exclusively on loss of heterozygosity analysis for tumor classification.

Prognostic value of the MIB-1 labeling index for central neurocytomas.

Although central neurocytomas are generally described as benign CNS lesions, malignant behavior including craniospinal dissemination and tumor-related death may occur. This meta-analysis was performed to investigate the prognostic value of the MIB-1 labeling index. Data were obtained not from the literature alone but also from contact with the authors. The data suggested an MIB-1 index score of >3% to be associated with a worse prognosis for local control (p < 0.0001) and survival (p = 0.0004).

[The revised WHO classification of brain tumors. Radiological aspects of 4 new tumor entities]. / Die revidierte WHO-Klassifikation der Hirntumoren. Radiologische Aspekte unter besonderer Berücksichtigung von vier neuen Tumorentitäten.

PURPOSE: Characterisation of the classification of brain tumours authorized by the WHO. METHOD OF APPRAISAL: This classification was revised and published in its second version. In the revision, some tumours were regrouped histogenetically and some tumour variants were added. Radiologically relevant changes of the classification include the differentiation of four new tumour entities that are easily distinguished by MR imaging. These four tumours belong to the group of childhood tumours or tumours occurring in early adulthood and are characterized by a good prognosis after extirpation. RESULTS OF APPRAISAL: Central neurocytomas are small-cyst ventricular tumours associated with the foramen of Monroi and show moderate contrast enhancement. Infantile desmoplastic gangliogliomas/astrocytomas commonly consist of a solid tumour portion related to the leptomeninges with pronounced contrast enhancement and a typically very large cyst. Pleomorphic xanthoastrocytomas are circumscribed cortical tumours and usually show very moderate gyriform enhancement with only slight signs of a mass effect. Dysembryoblastic neuroepithelial tumours, which originate in the cortical/ subcortical region, likewise show no mass effect; they are characterised by thickening of the cortex from surrounding dysplastic tissue and erosion of the calotte.