Neuro Oncology Diagnosis

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Questions and Answers

What is the approximate percentage of cases where incidental diagnosis is reported?

20%

30%

10% (correct)

What is the typical location of IDH-mutant and 1p/19q-codeleted oligodendrogliomas on CT?

Cerebellum

Cortex and subcortical white matter (correct)

Brainstem

Spinal cord

What is the significance of calcifications in IDH-mutant and 1p/19q-codeleted oligodendrogliomas?

They are a sign of poor prognosis

They are diagnostic

They are not diagnostic (correct)

They are a sign of favourable prognosis

What is the approximate percentage of CNS WHO grade 3 oligodendrogliomas that show gadolinium contrast enhancement?

70% Signup and view all the answers

What is the characteristic of IDH-mutant and 1p/19q-codeleted oligodendrogliomas on T1-weighted MRI?

T1-hypointense Signup and view all the answers

What is the characteristic of IDH-mutant and 1p/19q-codeleted oligodendrogliomas compared to IDH-mutant diffuse astrocytomas of corresponding grade?

Higher microvascularity Signup and view all the answers

What is the significance of intratumoural haemorrhages in IDH-mutant and 1p/19q-codeleted oligodendrogliomas?

They are not diagnostic Signup and view all the answers

What is the characteristic of IDH-mutant and 1p/19q-codeleted oligodendrogliomas on T2-weighted MRI?

T2-hyperintense Signup and view all the answers

What is the common feature of IDH-mutant and 1p/19q-codeleted oligodendrogliomas on imaging?

Indistinct tumour margins Signup and view all the answers

What is the significance of areas of cystic degeneration in IDH-mutant and 1p/19q-codeleted oligodendrogliomas?

They are not diagnostic Signup and view all the answers

What is the primary limitation of magnetic resonance spectroscopy and radiomics in differentiating 1p/19q-codeleted and 1p/19q-intact low-grade diffuse gliomas?

Limited sensitivity and specificity Signup and view all the answers

What is a new means of non-invasively detecting IDH-mutant gliomas using magnetic resonance spectroscopy?

Detection of 2-hydroxyglutarate levels Signup and view all the answers

What is the potential use of PET imaging in IDH-mutant gliomas?

Distinguishing between CNS WHO grade 2 and 3 IDH-mutant gliomas Signup and view all the answers

What is a characteristic pattern of spread of IDH-mutant and 1p/19q-codeleted oligodendrogliomas?

Gliomatosis cerebri pattern Signup and view all the answers

What is a rare occurrence in some patients with IDH-mutant and 1p/19q-codeleted oligodendrogliomas?

Extracranial metastases Signup and view all the answers

What is a common feature of patients with progressive IDH-mutant and 1p/19q-codeleted oligodendrogliomas?

Slow clinical deterioration despite large enhancing lesions Signup and view all the answers

What is a limitation of magnetic resonance spectroscopy in detecting IDH-mutant gliomas?

Technical challenges Signup and view all the answers

What is a characteristic of IDH-mutant and 1p/19q-codeleted oligodendrogliomas?

Diffuse growth pattern Signup and view all the answers

What is a potential application of PET imaging in IDH-mutant gliomas?

Grading IDH-mutant gliomas Signup and view all the answers

What is a feature of IDH-mutant and 1p/19q-codeleted oligodendrogliomas?

Diffuse growth pattern Signup and view all the answers

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.