Can you tell the glial tumors apart?

The Veterinary Journal 2013

January 29, 2025

R.T. Bentley, C.P. Ober, K.L. Anderson, et al.

Background
The study investigates the relationship between magnetic resonance imaging (MRI) criteria and the histopathological type and grade of gliomas in dogs. It aims to identify specific MRI features that can help differentiate tumor types (astrocytomas vs. oligodendrogliomas) and grades (low-grade vs. high-grade), given the limited ability to predict these characteristics ante-mortem in veterinary medicine.

Methods
A retrospective analysis was conducted on 31 dogs diagnosed with gliomas through histopathology. MRIs were performed prior to histological confirmation, and imaging data were interpreted by five blinded investigators. Standardized grading instructions were used to assess 18 MRI criteria. Statistical analyses included univariate and multivariate methods to evaluate relationships between MRI features and tumor characteristics.

Results
Key findings include:

-Tumor Grade: Grade II gliomas were more often associated with mild or no contrast enhancement, absence of cystic structures, and superficial locations relative to the internal capsule. High-grade gliomas displayed more extensive contrast enhancement and cystic regions.

-Tumor Type: Astrocytomas were linked to moderate-to-extensive peritumoral edema, lack of ventricular distortion, and isointense or hyperintense T1-weighted signals. Oligodendrogliomas were more likely to distort ventricles.

-Overall inter-observer agreement on MRI evaluation was moderate, with some criteria (e.g., tumor origin, T1-weighted signal intensity) showing excellent agreement.

Limitations
The study's retrospective nature introduces potential variability in imaging protocols and therapeutic interventions prior to MRI. Limited sample size precludes detailed subtype analysis (e.g., comparing specific grades of astrocytomas and oligodendrogliomas). Histological confirmation via biopsy may underestimate tumor grade due to sampling limitations.

Conclusions
MRI features can help predict glioma grade and type in dogs, aiding clinical decision-making. Mild contrast enhancement and absence of cystic regions suggest a lower tumor grade, while significant peritumoral edema and minimal ventricular distortion favor astrocytoma diagnoses. These findings enhance the utility of MRI in non-invasive glioma assessment in veterinary practice. Further studies are needed to refine these criteria and validate their diagnostic reliability.

Canine intracranial gliomas: grade II (A – astroctyoma), grade III (B – olidodendroglioma) and grade IV (C – glioblastoma). From left to right: Hematoxylin and eosin stained photomicrographs, T1W and T1W post-contrast transverse magnetic resonance images. The grade II astrocytoma is non-enhancing and superficially located (arrow). Histopathologically, it displays no microvascular proliferation or necrosis. The grade III oligodendroglioma is in a deeper location, contains multiple intra-tumoral fluid accumulations, and is severely enhancing in a ring-like pattern. Histopathologically, it is intermediate, displaying microvascular proliferation. The glioblastoma displays severe ring enhancement and a single cyst. Histopathologically, necrosis and cavitation, microvascular proliferation and profound pleomorphism are present

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