Abstract
We have previously published a study on the reliable detection of 2-hydroxyglutarate (2HG) in lower-grade gliomas by magnetic resonance spectroscopy (MRS). In this short article, we re-evaluated five glioma cases originally assessed as isocitrate dehydrogenase (IDH) wildtype, which showed a high accumulation of 2HG, and were thought to be false-positives. A new primer was used for the detection of IDH2 mutation by Sanger sequencing. Adequate tissue for DNA analysis was available in 4 out of 5 cases. We found rare IDH2 mutations in two cases, with IDH2 R172W mutation in one case and IDH2 R172K mutation in another case. Both cases had very small mutant peaks, suggesting that the tumor volume was low in the tumor samples. Thus, the specificity of MRS for detecting IDH1/2 mutations was higher (81.3%) than that originally reported (72.2%). The detection of 2HG by MRS can aid in the diagnosis of rare, non-IDH1-R132H IDH1 and IDH2 mutations in gliomas.
Highlights
Isocitrate dehydrogenase (IDH)-mutant gliomas produce the oncometabolite2-hydroxyglutarate (2HG)
We previously reported on the reliable detection of 2HG by 3.0-tesla magnetic resonance spectroscopy (MRS) in a cohort of 52 lower-grade glioma patients (WHO grades 2 and 3) [1]
We re-evaluated five gliomas initially assessed to be of IDH wildtype but showed a high accumulation of 2HG and were thought to be false-positive
Summary
Isocitrate dehydrogenase (IDH)-mutant gliomas produce the oncometabolite2-hydroxyglutarate (2HG). We previously reported on the reliable detection of 2HG by 3.0-tesla magnetic resonance spectroscopy (MRS) in a cohort of 52 lower-grade glioma patients (WHO grades 2 and 3) [1]. A cutoff of 1.489 mM for 2HG yielded 100% sensitivity and a 72.2% specificity for the detection of IDH1 or IDH2 mutations was reported. A high level of 2HG was detected in 5 of 27 (18.5%) gliomas that were determined to be IDH-wildtype. These were thought to be false-positive results or a failure to detect rare IDH1 or IDH2 mutations by DNA sequencing [1]. An analysis of IDH1/2 mutations using Sanger sequencing revealed an IDH2 mutation. We re-evaluated IDH1 and IDH2 status in the remaining “false-positive”
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