Oligodendroglial tumors are heterogenous neoplasms with histologic features shared with other central nervous system tumors, such as dysembryoplastic neuroepithelial tumors.
We examined a series of tumors, identified as possessing oligodendroglial components at the time of intraoperative examination, to see if molecular subsets based on the oligodendroglial component could be recognized.
DNA was extracted from fresh brain tumor tissue and corresponding peripheral blood or normal tissues. Genotypes for multiple loci were determined by polymerase chain reaction amplification using fluorescent-labeled primers for markers on chromosomes 1p, 17p, and 19q.
Of the 12 oligodendrogliomas, 6 (60%) of 10 informative cases for 1p exhibited loss of heterozygosity (LOH). Six (50%) of 12 informative cases for 19q exhibited LOH. Each case also showed LOH at 1p. Three (25%) of 12 informative cases exhibited LOH at 17p for the dinucleotide repeat within the TP53 gene. In oligoastrocytomas, none of 4 informative cases showed LOH at 1p, 1 (25%) showed LOH at 19q, and 2 (50%) at 17p. One case also displayed microsatellite instability at 3 of 8 markers. In the 3 anaplastic oligodendrogliomas, 1 was not informative for 1p and none of the informative tumors exhibited LOH at 1p or 17p; 1 case (33%) exhibited LOH at 19q. Of the 14 informative anaplastic oligoastrocytomas, LOH was seen in 5 (36%) at both 1p and 19q and in 2 (14%) at 17p. Those with allelic loss at TP53 were astrocytoma predominant. No dysembryoplastic neuroepithelial tumors exhibited LOH at any marker on 1p, 17p, or 19q.
These findings suggest that routine screening for allelic losses, in samples intraoperatively determined to have an oligodendroglial component, will reveal prognostically or therapeutically relevant information in the majority of cases.
"Altérations cytogénétiques et moléculaires présentes dans les gliomes                               De nombreuses altérations cytogénétiques ont été retrouvées dans les gliomes, les plus fréquentes étant des délétions de 1p, 9p, 10, 13q, 17p, 19q, 22q et des gains sur le chromosome 7   . Ces altérations sont rares dans les gliomes de bas grade, mais leur fréquence augmente avec la progression tumorale et l'acquisition de caractères d'agressivité biologique. "
[Show abstract][Hide abstract] ABSTRACT: La meilleure connaissance de l'histoire spontanée des gliomes de grade II de l'Organisation mondiale de la santé (OMS), à savoir la croissance régulière, l'infiltration le long des faisceaux de substance blanche et surtout le risque de transformation anaplasique – menaçant ainsi les pronostics fonctionnel et vital – associée à une minimisation des risques de traitements, a transformé l'attitude abstentionniste « classique » en une attitude résolument thérapeutique. Le but est dorénavant de tendre vers l'élaboration de véritables stratégies thérapeutiques adaptées à chaque patient, à savoir de déterminer l'ordre et le moment de chacun des traitements (1 re voire 2 e exérèse chirurgicale, 1 re voire 2 e ligne de chimiothérapie, radiothérapie) en fonction de l'évolution tumorale (mesurée sur les images en résonance magnétiques régulières de contrôle), de l'état clinique et neuropsychologique ainsi que de l'organisation anatomofonctionnelle cérébrale individuelle (étudiée grâce aux méthodes de cartographie), afin d'éviter la transformation maligne le plus longtemps possible tout en préservant la qualité de vie, cette tumeur survenant le plus souvent chez des patients jeunes avec une vie familiale et une activité socioprofessionnelle normales.
[Show abstract][Hide abstract] ABSTRACT: Central nervous system (CNS) neoplasms can be diagnostically challenging, due to remarkably wide ranges in histologic appearance, biologic behavior, and therapeutic approach. Nevertheless, accurate diagnosis is the critical first step in providing optimal patient care. As with other oncology-based specialties, there is a rapidly expanding interest and enthusiasm for identifying and utilizing new biomarkers to enhance the day-to-day practice of surgical neuropathology. In this regard, the field is primed by recent advances in basic research, elucidating the molecular mechanisms of tumorigenesis and progression in the most common adult and pediatric brain tumors. Thus far, few have made the transition into routine clinical practice, the most notable example being 1p and 19q testing in oligodendroglial tumors. However, the field is rapidly evolving and many other biomarkers are likely to emerge as useful ancillary diagnostic, prognostic, or therapeutic aids. The goal of this article is to highlight the most common genetic alterations currently implicated in CNS tumors, focusing most on those that are either already in common use in ancillary molecular diagnostics testing or are likely to become so in the near future.
[Show abstract][Hide abstract] ABSTRACT: Demonstration of the loss of chromosomes 1p and 19q in the presence of a brain neoplasm marks the emergence of genotype as a prognostic indicator. The authors report gene expression data for oligodendroglioma and correlate genotype with response to therapy. Gene expression subgroups may represent distinct types of disease.
Eighty-seven cases of supratentorial oligodendroglioma were selected from 145 cases treated in a single center between January 1990 and December 2001. Fluorescence in situ hybridization was used to determine the status of chromosomes 1p and 19q. Parameters evaluated included clinical data and radiological and histological features. Univariate and multivariate analyses were performed and a probability value less than 0.05 was considered significant. The patients included 48 women and 39 men. The overall mean age at presentation was 45 years for women and 36 years for men (p = 0.006). The univariate analysis identified the following as favorable prognostic factors: younger patient age (p = 10(-5)), female sex (p = 0.0025), seizure as a presenting symptom (p = 10(-5)), normal clinical examination (p = 10(-5)), absence of lesion enhancement on neuroimaging studies (p = 0.0231), lack of histological necrosis (p = 0.0003), absence of mitoses (p = 0.0014), 1p and 19q deletions (p = 0.0001), absence of recurrence (p = 0.0021), and adjuvant radiotherapy and/or chemotherapy (p = 10(-5)). The multivariate analysis identified patient age (p = 10(-5)) and chromosomal anomalies (p = 0.002) as independently linked to survival. Three molecular subtypes emerged: oligodendroglioma with 1p and 19q deletions, oligodendroglioma demonstrating polysomia and a lack of meaningful response to radiotherapy or chemotherapy, and oligodendroglioma with no 1p-9q deletion in which partial response was seen.
According to our data, oligodendrogliomas could be divided into three molecular subtypes. Although chemotherapy seems efficient for managing this tumor, additional studies should be conducted to compare the efficacy of radiotherapy and chemotherapy.
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