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What is the approximate percentage of cases where incidental diagnosis is reported?
What is the typical location of IDH-mutant and 1p/19q-codeleted oligodendrogliomas on CT?
What is the significance of calcifications in IDH-mutant and 1p/19q-codeleted oligodendrogliomas?
What is the approximate percentage of CNS WHO grade 3 oligodendrogliomas that show gadolinium contrast enhancement?
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What is the characteristic of IDH-mutant and 1p/19q-codeleted oligodendrogliomas on T1-weighted MRI?
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What is the characteristic of IDH-mutant and 1p/19q-codeleted oligodendrogliomas compared to IDH-mutant diffuse astrocytomas of corresponding grade?
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What is the significance of intratumoural haemorrhages in IDH-mutant and 1p/19q-codeleted oligodendrogliomas?
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What is the characteristic of IDH-mutant and 1p/19q-codeleted oligodendrogliomas on T2-weighted MRI?
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What is the common feature of IDH-mutant and 1p/19q-codeleted oligodendrogliomas on imaging?
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What is the significance of areas of cystic degeneration in IDH-mutant and 1p/19q-codeleted oligodendrogliomas?
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What is the primary limitation of magnetic resonance spectroscopy and radiomics in differentiating 1p/19q-codeleted and 1p/19q-intact low-grade diffuse gliomas?
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What is a new means of non-invasively detecting IDH-mutant gliomas using magnetic resonance spectroscopy?
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What is the potential use of PET imaging in IDH-mutant gliomas?
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What is a characteristic pattern of spread of IDH-mutant and 1p/19q-codeleted oligodendrogliomas?
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What is a rare occurrence in some patients with IDH-mutant and 1p/19q-codeleted oligodendrogliomas?
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What is a common feature of patients with progressive IDH-mutant and 1p/19q-codeleted oligodendrogliomas?
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What is a limitation of magnetic resonance spectroscopy in detecting IDH-mutant gliomas?
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What is a characteristic of IDH-mutant and 1p/19q-codeleted oligodendrogliomas?
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What is a potential application of PET imaging in IDH-mutant gliomas?
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What is a feature of IDH-mutant and 1p/19q-codeleted oligodendrogliomas?
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Study Notes
Diagnosing Oligodendrogliomas
- Proliferation markers like Ki-67 (MIB1) and clinical/neuroradiological features (e.g. rapid symptomatic growth and contrast enhancement) may provide additional information in borderline cases.
- Homozygous deletion involving the CDKN2A and/or CDKN2B locus is found in a small subset (~30%) of oligodendrogliomas.
- Immunohistochemical detection of IDH1 p.R132H expression and preserved nuclear ATRX expression is not sufficient to diagnose an IDH-mutant and 1p/19q-codeleted oligodendroglioma, even with classic histology.
Molecular Characteristics
- Most IDH-mutant and 1p/19q-codeleted oligodendrogliomas carry TERT promoter mutations.
- Detection of a TERT promoter mutation in an IDH-mutant glioma is not sufficient for an oligodendroglioma diagnosis, as rare cases are TERT-wildtype.
- TERT promoter mutations are also observed in a subset of 1p/19q-intact IDH-mutant astrocytomas.
DNA Methylation Array Analysis
- DNA methylation array analysis reveals a diagnostic molecular profile by combining the detection of an oligodendroglioma-associated methylation signature and 1p/19q codeletion.
Pathogenesis
- The cell (or cells) of origin of IDH-mutant and 1p/19q-codeleted oligodendroglioma remains unknown.
Imaging
- IDH-mutant and 1p/19q-codeleted oligodendrogliomas usually appear on CT as hypodense or isodense mass lesions that are typically located in the cortex and subcortical white matter.
- Calcifications are commonly seen, but they are not diagnostic; some tumours show intratumoural haemorrhages and/or areas of cystic degeneration.
- MRI typically shows a T1-hypointense and T2-hyperintense mass with indistinct tumour margins.
- Gadolinium contrast enhancement can be detected in ~70% of CNS WHO grade 3 oligodendrogliomas, where it is associated with microvascular proliferation and less favourable prognosis.
Diagnostic Features of IDH-Mutant and 1p/19q-Codeleted Oligodendrogliomas
- Ki-67 (MIB1) and clinical/neuroradiological features may provide additional information in borderline cases
- Homozygous deletion of CDKN2A and/or CDKN2B locus is found in a small subset (~30%) of cases
- IDH1 p.R132H expression and preserved nuclear ATRX expression are not sufficient for diagnosis without 1p/19q codeletion
- 1p/19q analysis is critical for accurate molecular diagnosis in IDH-mutant gliomas with preserved nuclear ATRX expression
- Most IDH-mutant and 1p/19q-codeleted oligodendrogliomas carry TERT promoter mutations
- Detection of TERT promoter mutation is not sufficient for oligodendroglioma diagnosis, as rare cases are TERT-wildtype
Imaging Features
- IDH-mutant and 1p/19q-codeleted oligodendrogliomas typically appear as hypodense or isodense mass lesions on CT
- Calcifications are commonly seen, but not diagnostic
- MRI typically shows a T1-hypointense and T2-hyperintense mass with indistinct tumour margins
- Gadolinium contrast enhancement is detected in ~70% of CNS WHO grade 3 oligodendrogliomas, associated with microvascular proliferation and less favourable prognosis
- IDH-mutant and 1p/19q-codeleted oligodendrogliomas show higher microvascularity and higher vascular heterogeneity than IDH-mutant diffuse astrocytomas
Additional Diagnostic Techniques
- Magnetic resonance spectroscopy and radiomics can identify differences between 1p/19q-codeleted and 1p/19q-intact low-grade diffuse gliomas, but have limited sensitivity and specificity
- Demonstration of elevated 2-hydroxyglutarate levels by magnetic resonance spectroscopy is a new means of non-invasively detecting IDH-mutant gliomas
- PET imaging may allow the distinction between CNS WHO grade 2 and 3 IDH-mutant gliomas, but reported series tend to be small and unvalidated
Spread of Oligodendrogliomas
- IDH-mutant and 1p/19q-codeleted oligodendrogliomas characteristically extend into adjacent brain in a diffuse manner
- They occasionally have a gliomatosis cerebri pattern
- Distant leptomeningeal spread may occur in some patients, especially in late-stage disease
- Rare cases of extracranial metastases of oligodendrogliomas, mostly CNS WHO grade 3, have been reported
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Description
Assessing diagnosis of neuro-oncological conditions using proliferation markers, clinical features, and genetic testing. This quiz covers the role of Ki-67, CDKN2A, CDKN2B, IDH1, and ATRX in diagnosis.
