Dysembryoplastic neuroepithelial tumor: an immunohistochemical study with myelin oligodendrocyte glycoprotein

Malignant dysembryoplastic neuroepithelial tumour in a zebrafish (Danio rerio)

Neuroectodermal tumours in man, including medulloblastoma, medulloepithelioma, neuroblastoma, esthesioneuroblastoma, primitive neuroectodermal tumour and dysembryoplastic neuroepithelial tumour, typically occur in children and young adults. These tumour types are occasionally observed in juvenile and adult zebrafish (Danio rerio) either as induced tumours in carcinogen-exposed zebrafish or as an incidental finding in zebrafish≥2years of age. An adult zebrafish submitted for routine histological examination was sent for a second opinion consultation after an uncharacteristic brain mass was identified. Microscopically, the expansile and infiltrative extracortical mass arising from the cerebellum had a diffuse microcystic pattern with solid hypercellular regions occupying 80% of the extrameningeal space and effacing the endomeninx and significantly displacing the metencephalon. The mass was composed of dense sheets of oligodendrocyte-like cells, random neurons and pseudocysts containing 'floating neurons' within a scant mucinous matrix. Neoplastic cells demonstrated positive perinuclear and intracytoplasmic expression of S-100. Malignant dysembryoplastic neuroepithelial tumour was diagnosed based on the histological features of the brain mass, which were indistinguishable from the human tumour. To our knowledge, this is the first report of a dysembryoplastic neuroepithelial tumour in a zebrafish.

Dysembryoplastic neuroepithelial tumors: a prospective clinicopathologic and outcome study of 13 children

Dysembryoplastic neuroepithelial tumors (DNETs) are benign intracortical masses that are typically observed in children and young adults and are classified as glioneuronal tumors (WHO grade I). Large and retrospective series of patients with DNETs have been reported, but prospective studies on pediatric cohorts of patients with DNETs have been lacking. In the present study, 13 children (8 boys, 5 girls; age 8-18 years) who had simple (n = 2) or complex (n = 11) partial seizures (seizure duration range, 2-4 years; mean, 1.5 years; mode, 1.2 years) were prospectively enrolled and monitored over 13 years. The DNETs were located in the frontal (n = 2), temporal (n = 9), or occipital (n = 2) cortex. In 11/13 cases, the seizures were resistant to drug therapy, and all the children had surgery consisting of extended lesionectomy coupled with neuronavigation. Pathology examination revealed cortical dysplasia (n = 8), glial nodules (n = 11), calcification (n = 4), cellular atypia (n = 3), endothelial proliferation (n = 1), perivascular inflammation (n = 3), and meningeal involvement (n = 6). All children were seizure free throughout postsurgical follow-up of 2-11 years. This first prospective study with follow-up monitoring of a childhood population with DNETs confirms, on a long-term basis, that the coupled strategy of extended lesionectomy and neuronavigation has good outcome for long-term seizure control.

Newly defined central nervous system neoplasms

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

Extraventricular neurocytoma: morphological and immunohistochemical considerations on differential diagnosis

Neurocytoma is an unusual neuronal tumor especially affecting young people. It commonly arises in the ventricles and has a benign outcome. Herein, we report on a rare case of extraventricular neurocytomas (right parietal lobe) in a young girl admitted to hospital for a cranial trauma subsequent to a seizure. The tumor, radiologically well-circumscribed, cystic and enhancing, was surgically excised. The patient, who received no post surgical treatment, is alive and well after 18 months of follow-up. Pathological examination showed a well-differentiated lesion composed of uniform, round cells with perinuclear halos in a neuropil background and immunohistochemically positive for neuronal markers (synaptophysin, neuron-specific enolase, neurofilaments). The authors emphasize the role of the morphological and immunohistochemical evaluations to recognize this rare tumor.

Chromosome 1p allelic loss by fluorescence in situ hybridization is not observed in dysembryoplastic neuroepithelial tumors

Differentiation of dysembryoplastic neuroepithelial tumor (DNT) from cystic low-grade oligodendroglioma, particularly in a limited biopsy orfragmented specimen, may be impossible. Research has shown that allelic loss of chromosome 1p is a relatively common finding in oligodendrogliomas. Little is known about chromosome 1p status in DNT. We retrospectively evaluated 14 DNTs for loss of heterozygosity (LOH) on chromosome 1p by fluorescence in situ hybridization (FISH) and compared the results with 1p FISH analysis in 57 low-grade oligodendrogliomas (World Health Organization grade II). The 14 DNTs arose in 8 females and 6 males (mean age, 20.9 years at the time of surgery). All 14 DNTs were 1p intact by FISH analysis. The 57 low-grade oligodendrogliomas arose in 31 males and 26 females (mean age, 43.2 years). LOH on chromosome 1p was present in 31 (54%) of 57 tumors; the remaining 26 tumors were 1p intact. LOH on chromosome 1p is not a feature of DNTs. LOH on chromosome 1p may be a useful differential diagnostic feature (favoring oligodendroglioma) in a subset of cases in which specimen fragmentation or size raises the differential diagnosis of DNT vs oligodendroglioma.

MAP-2e, a novel MAP-2 isoform, is expressed in gliomas and delineates tumor architecture and patterns of infiltration

The MAP-2 isoform containing exon 13 (MAP-2e) is expressed in human fetal development as early as 15 gestational weeks and parallels oligodendrocyte maturation. MAP-2e is down-regulated following myelination and is expressed in few cells in the adult central nervous system (CNS). To determine whether CNS tumors express MAP-2e, we screened 122 archival, paraffin-embedded adult and pediatric tumors of the CNS and non-CNS. All oligodendrogliomas were positive and extensive staining was observed in glioblastomas, various malignant gliomas and dysembryoplastic neuroepithelial tumors. MAP-2e was not expressed in non-CNS tumors or neuroblastomas. Thus. neuroectodermal tumors that have glial characteristics express this developmental marker of immature glia. Analysis of oligodendrogliomas demonstrated numerous cell morphologies from round cells with no processes to cells with single or multiple processes. MAP-2e immunostaining also delineated tumor invasion into adjacent gray and white matter, indicating that MAP-2e appears to be a useful marker for examining the infiltration of malignant cells into surrounding tissue.