Glioblastomas with Oligodendroglial Component – Common Origin of the Different Histological Parts and Genetic Subclassification

Abstract

Abstract.Background: Glioblastomas are the most common and most malignant brain tumors in adults. A small subgroup of glioblastomas contains areas with histological features of oligodendroglial differentiation (GBMO). Our objective was to genetically characterize the oligodendroglial and the astrocytic parts of GBMOs and correlate morphologic and genetic features with clinical data.Methods: The oligodendroglial and the "classic" glioblastoma parts of 13 GBMO were analyzed separately by interphase fluorescence in situ hybridization (FISH) on paraffin sections using a custom probe set (regions 1p, 1q, 7q, 10q, 17p, 19q, cen18, 21q) and by comparative genomic hybridization (CGH) of microdissected paraffin embedded tumor tissue.Results: We identified four distinct genetic subtypes in 13 GBMOs: an "astrocytic" subtype (9/13) characterized by +7/−10; an "oligodendroglial" subtype with −1p/−19q (1/13); an "intermediate" subtype showing +7/−1p (1/13), and an "other" subtype having none of the former aberrations typical for gliomas (2/13). The different histological tumor parts of GBMO revealed common genetic changes in all tumors and showed additional aberrations specific for each part.Conclusion: Our findings demonstrate the monoclonal origin of GBMO followed by the development of the astrocytic and oligodendroglial components. The diagnostic determination of the genetic signatures may allow for a better prognostication of the patients.

Status of O 6 -methylguanine-DNA methyltransferase [MGMT] gene promoter methylation among patients with glioblastomas from India

“…[32] A very recent report that included extensive molecular characterization of both glioblastomas and GBMOs, however, shows that GBMOs are associated with better median survival. [33] Whether molecular mechanisms that result in this histological phenotype have a synergy with the mechanisms that contribute to methylation of the promoter thereby leading to a better outcome, is perhaps a feature worth investigating in a larger set of GBMOs in future.…”

Radiological imaging features of glioblastoma with oligodendroglioma component: a comparison with conventional glioblastoma

“…It is of clinical importance that the prognosis of GBMO is better than that of cGBM because GBMO frequently involves the loss of heterozygosity (LOH) 1p/19q, which is a good prognostic factor in oligodendroglioma, IDH1 mutation, etc. (7–9,20,21). Several studies report that GBMO has a significantly better prognosis than cGBM (5,9,10,22).…”

Synchronous multicentric glioblastoma with PNET and O subtypes: Possible pathogenesis

“…This subtype of GBM represents about 5-18% of all malignant gliomas. [1527] Their molecular alterations include EGFR, p53, IDH1, MGMT, loss of chromosome 1p, 9p21, 10, 19q, and gain of chromosome 7. GBM-Os may resemble GBMs on histology, but at the same time, they contain areas resembling oligodendrogliomas.…”

“…[11] Studies have shown that patients with GBM-O tend to be younger, and the tumours are more chemosensitive, conferring a favorable prognosis. [131229] In view of the inter-tumoral differences within the same patient and, based on our current understanding of GBM, we postulate that the key to our patient's MCGBM lies in the origin of the cells responsible for malignant gliomas.…”