1p/19q co-deleted fibrillary astrocytomas: Not everything that is co-deleted is an oligodendroglioma

Andrews, Cyril; Prayson, Richard A.

doi:10.1016/j.anndiagpath.2020.151519

Cited by 5 publications

(4 citation statements)

References 22 publications

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“…In 11 cases (6 of 11 harbored IDH1-R132 mutations, the remaining 5 were IDH1/IDH2 wild type) the NGS panel obtained different results (11 of 60 cases; 18.3%) (Table 4). To our knowledge, the overall rate of false-positive FISH 1p/19q codeletion reported in the literature is lower (range, 2% to 8%), 7,9,12,19 however, these studies focused mainly on grade II and grade III diffuse gliomas, substantially ruling out glioblastomas, which are responsible for the doubling of the rate in the cohort analyzed.…”

Section: Discussionmentioning

confidence: 87%

“…15 Less well known is the fact that standard FISH analysis may overdiagnose 1p/19q codeletion cases that have partial chromosome alterations. 12 It is easy to recognize those cases in which the sequencing of IDH1 and IDH2 is wild type in the face of 1p/19q codeletion by FISH. It is difficult to recognize the cases with partial chromosome alterations mistakenly scored 1p/19q codeletd by FISH that are IDH1/IDH2 mutated.…”

Section: Discussionmentioning

confidence: 99%

“…9,10 To date, fluorescence in situ hybridization (FISH) is the most common technique for detection of 1p/ 19q codeletion and currently is considered the gold standard, 11 although the possibility of false-positive FISH results already is known. 12 In this study, a high-density single-nucleotide polymorphism (SNP) panel was developed to analyze 1p/19q codeletion in brain tumors using next-generation sequencing (NGS) combined with IDH1 and IDH2 mutational analysis. The results obtained using this 1p/19q SNP-IDH panel were compared with those from the gold standard FISH analysis.…”

mentioning

confidence: 99%

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Next-Generation Sequencing Panel for 1p/19q Codeletion and IDH1-IDH2 Mutational Analysis Uncovers Mistaken Overdiagnoses of 1p/19q Codeletion by FISH

Biase

Acquaviva

Visani

et al. 2021

The Journal of Molecular Diagnostics

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Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Next-Generation Sequencing Panel for 1p/19q Codeletion and IDH1-IDH2 Mutational Analysis Uncovers Mistaken Overdiagnoses of 1p/19q Codeletion by FISH

Biase

Acquaviva

Visani

et al. 2021

The Journal of Molecular Diagnostics

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“…This genetic alteration results from the combined deletion of entire 1p19q after unbalanced translocation between chromosomes 1 and 19 [t(1:19)(q10;p10)] [8]. Although there are currently no available molecular markers that reliably distinguish oligodendroglial tumours from astrocytomas, 1p19 co-deletion has been considered as one of the hallmark criteria for the diagnosis of oligodendroglioma, based on the 2016 World Health Organization (WHO) Classification of Tumours of the Central Nervous System (CNS) [1,8,10]. Hence, recent clinical trials have approved the associations between 1p19q co-deletion and prolonged overall survival of patients treated with radiation with or without chemotherapy [3,4].…”

Section: Introductionmentioning

confidence: 99%

Can oligodendrocyte transcriptional factor-2 (Olig2) be used as an alternative for 1p/19q co-deletions to distinguish oligodendrogliomas from other glial neoplasms?

Kurdi¹,

Alkhatabi²,

Butt³

et al. 2021

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Aim of the study: Oligodendrocyte transcriptional factor-2 (Olig2) is an essential marker for oligodendrocytes expression. We aimed to explore the expression of Olig2 in different glial neoplasms and to investigate if diffuse Olig2 expression can replace 1p19q co-deletion for the diagnosis of oligodendroglioma. Material and methods: Olig2 was performed on 53 samples of different glial neoplasms using immunohistochemistry (IHC). 1p/19q deletions were investigated using fluorescence in situ hybridization (FISH).Results: Olig2 labelling of different glial neoplasms revealed various expressions, in which 26 tumours showed diffuse expression (≥ 60%) and 23 tumours showed partial focal expression (< 50%). Four tumours showed no expression. Of the 26 tumours, 6 oligodendrogliomas had 1p19q co-deletion and the remaining 3 oligodendrogliomas showed no co-deletion. Three non-oligodendroglial tumours were found to have 19q deletion. The FISH of the remaining tumours (14/26) showed no aberrations. There was no significant difference in the final diagnosis by using 1p19q co-deletion test among glial neoplasms with diffuse Olig2 expression (p = 0.248). Conclusions: Olig2 marker cannot be used as an alternative diagnostic method for 1p19q co-deletion to distinguish oligodendrogliomas from other glial neoplasms. Although some glial tumours showed diffuse Olig2 expression, 1p19q co-deletion testing is the best diagnostic method.

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Frequency of false-positive FISH 1p/19q codeletion in adult diffuse astrocytic gliomas

Ball

Kollmeyer

Praska

et al. 2020

Neuro-Oncology Advances

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Background Oligodendroglioma is genetically defined by concomitant IDH (IDH1/IDH2) mutation and whole-arm 1p/19q codeletion. Codeletion of 1p/19q traditionally evaluated by FISH cannot distinguish partial from whole-arm 1p/19q codeletion. Partial 1p/19q codeletion called positive by FISH is diagnostically a “false positive” result. Chromosomal microarray (CMA) discriminates partial from whole-arm 1p/19q codeletion. Herein, we aimed to estimate the frequency of partial 1p/19q codeletion that would lead to a false positive FISH result. Methods FISH 1p/19q codeletion test probe coordinates were mapped onto Oncoscan CMA data to determine the rate of partial 1p/19q codeletion predicted to be positive by FISH. Diffuse astrocytic gliomas with available CMA data (2015-2018) were evaluated and classified based on IDH1-R132H/ATRX/p53 immunohistochemistry, IDH/TERT promoter targeted sequencing and/or CMA according to classification updates. Predicted false positive cases were verified by FISH whenever possible. Results The overall estimated false positive FISH 1p/19q codeletion rate was 3.6% (8/223). Predicted false positives were verified by FISH in 6 (of 8) cases. False positive rates did not differ significantly (p=0.49) between IDH-mutant (4.6%; 4/86) and IDH-wildtype (2.9%; 4/137) tumors. IDH-wildtype false positives were all WHO grade IV, whereas IDH-mutant false positives spanned all WHO grades. Testing for 1p/19q codeletion would not have been indicated for most false positives based on current classification recommendations. Conclusions Selective 1p/19q codeletion testing and cautious interpretation for conflicting FISH and histopathological findings are recommended to avoid potential misdiagnosis.

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1p/19q co-deleted fibrillary astrocytomas: Not everything that is co-deleted is an oligodendroglioma

Cited by 5 publications

References 22 publications

Next-Generation Sequencing Panel for 1p/19q Codeletion and IDH1-IDH2 Mutational Analysis Uncovers Mistaken Overdiagnoses of 1p/19q Codeletion by FISH

Next-Generation Sequencing Panel for 1p/19q Codeletion and IDH1-IDH2 Mutational Analysis Uncovers Mistaken Overdiagnoses of 1p/19q Codeletion by FISH

Can oligodendrocyte transcriptional factor-2 (Olig2) be used as an alternative for 1p/19q co-deletions to distinguish oligodendrogliomas from other glial neoplasms?

Frequency of false-positive FISH 1p/19q codeletion in adult diffuse astrocytic gliomas

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