Genetically Defined Oligodendroglioma Is Characterized by Indistinct Tumor Borders at MRI

Area of Science:

• Neuro-oncology
• Radiology
• Molecular Pathology

Background:

• The 2016 World Health Organization (WHO) classification of brain tumors redefined oligodendroglioma based on IDH mutation and 1p/19q codeletion.
• Previous imaging characteristics were associated with morphologically defined oligodendrogliomas, necessitating evaluation for genetically defined tumors.

Purpose of the Study:

• To assess if established MR imaging features are still applicable to genetically defined oligodendrogliomas according to the 2016 WHO classification.
• To correlate 1p/19q codeletion status with specific imaging findings and apparent diffusion coefficient (ADC) values.

Main Methods:

• Retrospective analysis of 148 adult patients with WHO grade II/III infiltrating gliomas and oligodendroglial morphology.
• Evaluation of preoperative MR imaging features, including tumor borders and signal heterogeneity, and ADC values in relation to 1p/19q codeletion status.

Main Results:

• Sixty-one percent (90/148) of patients had 1p/19q codeleted tumors (genetically defined oligodendrogliomas).
• Genetically defined oligodendrogliomas predominantly showed noncircumscribed borders (92%) and heterogeneous signal intensity (99%) on T1- and/or T2-weighted imaging.
• Lower mean ADC values were predictive of 1p/19q codeletion (P = .0005).

Conclusions:

• Imaging characteristics of genetically defined oligodendrogliomas differ from those previously associated with morphologically defined tumors.
• Genetically defined oligodendrogliomas are frequently poorly circumscribed and exhibit heterogeneous signal intensity.
• These findings highlight the importance of integrating genetic information with imaging for accurate brain tumor classification.