Clinical features, diagnosis, and survival analysis of dogs with glioma

Abstract

Background: Gliomas in dogs remain poorly understood.

Objectives: To characterize the clinicopathologic findings, diagnostic imaging features and survival of a large sample of dogs with glioma using the Comparative Brain Tumor Consortium diagnostic classification.

Animals: Ninety-one dogs with histopathological diagnosis of glioma.

Methods: Multicentric retrospective case series. Signalment, clinicopathologic findings, diagnostic imaging characteristics, treatment, and outcome were used. Tumors were reclassified according to the new canine glioma diagnostic scheme.

Results: No associations were found between clinicopathologic findings or survival and tumor type or grade. However, definitive treatments provided significantly (P = .03) improved median survival time (84 days; 95% confidence interval [CI], 45-190) compared to palliative treatment (26 days; 95% CI, 11-54). On magnetic resonance imaging (MRI), oligodendrogliomas were associated with smooth margins and T1-weighted hypointensity compared to astrocytomas (odds ratio [OR], 42.5; 95% CI, 2.42-744.97; P = .04; OR, 45.5; 95% CI, 5.78-333.33; P < .001, respectively) and undefined gliomas (OR, 84; 95% CI, 3.43-999.99; P = .02; OR, 32.3; 95% CI, 2.51-500.00; P = .008, respectively) and were more commonly in contact with the ventricles than astrocytomas (OR, 7.47; 95% CI, 1.03-53.95; P = .049). Tumor spread to neighboring brain structures was associated with high-grade glioma (OR, 6.02; 95% CI, 1.06-34.48; P = .04).

Conclusions and clinical importance: Dogs with gliomas have poor outcomes, but risk factors identified in survival analysis inform prognosis and the newly identified MRI characteristics could refine diagnosis of tumor type and grade.

Keywords: astrocytoma; dog; magnetic resonance imaging; oligodendroglioma; prognosis; tumor grade; undefined glioma.

FIGURE 1

Transverse (A) and dorsal (B) T1‐weighted postcontrast magnetic resonance (MR) images of a ring‐enhancing high‐grade oligodendroglioma (HO) showing the typical features of butterfly glioma with extensive involvement of the corpus callosum leading to bihemispheric spread. Photomicrograph of the same HO as in (A) and (B) occupying the lumen of the lateral ventricle and infiltrating the cingulate gyrus (top of the figure) and the corpus callosum (bottom of the figure) (C). The inset shows neoplastic cells invading the corpus callosum towards the contralateral ventricle (the oval represents an area of higher neoplastic cell density). HE stain. Scale bar = 1 mm (inset 200 μm). Transverse fluid‐attenuation inversion recovery MR image at the level of the tentorium cerebelli demonstrating 2 heterogeneously hyperintense independent foci of a high‐grade astrocytoma (D). Dorsal T2‐weighted images obtained at the level of the red (E) and the yellow (F) dotted lines show the largest tumor in the cerebellum and a second focus in the right occipital lobe, respectively. Both foci were characterized by large sized anisokaryotic cell populations with scant cytoplasm growing in a solid pattern (G). A mitotic figure is present (arrow) as well as glomeruloid‐like vessels (arrowheads). HE stain. Scale bar = 50 μm. Midsagittal T2‐weighted images of a poorly defined, heterogeneously hyperintense HO extending from the fronto‐olfactory area to the diencephalon (H). Note the enlarged and hyperintense pituitary gland (arrow). Severe nonuniform enhancement of the pituitary gland was noted on T1‐weighted postcontrast images whereas this was mild for the intra‐axial tumor. Dorsal view of the unfixed base of the neurocranium in the same dog as (H) demonstrating an expanded pituitary gland (asterisk) (I). Photomicrograph of the pituitary gland of the dog in (H) and (I) revealing severe infiltration of the hypophyseal lobules by the neoplastic cell population (J). HE stain. Scale bar = 500 μm

FIGURE 2

Anatomic distribution of intracranial gliomas in 88 dogs classified according to the Comparative Brain Tumor Consortium diagnostic scheme (A). Specific location of 65 hemispheric gliomas (B). Note there were an additional 4 high‐grade oligodendrogliomas primarily located within the lateral ventricles

FIGURE 3

Midsagittal (A) and transverse (B) T2‐weighted magnetic resonance (MR) images of a heterogeneously hyperintense high‐grade oligodendroglioma at the level of C1 vertebra (arrow) identified as intradural‐extramedullary by both observers. Note the mass extension into the foramen magnum (arrowhead). Photomicrograph of the same tumor as (A) and (B) demonstrating a highly cellular proliferation in direct contact with the thickened pia mater (arrow) in the dorsal aspect of the spinal cord (C). Note the severe hemorrhages ventrally where the mass is compressing the spinal cord parenchyma (asterisk). HE stain. Scale bar = 500 μm. Transverse T1‐weighted postcontrast MR image of an extra‐axial nonuniformly contrast‐enhancing high‐grade astrocytoma ventral to the mesencephalon (arrow) (D). Formalin‐fixed transverse section of the brain at the level of (D) demonstrating the extra‐axial appearance of the tumor (arrow) (E). Photomicrograph of the paraffin‐embedded tumor in (D) and (E) showing a highly cellular proliferation spreading through the subarachnoid space ventral to the mesencephalon (asterisk) with multiple foci of hemorrhage (arrowheads) and necrosis (arrow) (F). HE stain. Scale bar = 500 μm

FIGURE 4

Transverse T2‐weighted magnetic resonance (MR) image of a high‐grade oligodendroglioma (HO) in the right frontal lobe (arrow) with smooth margins and in close contact with the lateral ventricle (asterisk) (A). Transverse T1‐weighted image of a hypointense to gray matter HO in the right temporal lobe (arrow) (B). Dorsal T2‐weighted MR image showing a high‐grade undefined glioma extending from the frontal (arrow) to the temporal lobe (arrowhead) (C). Involvement of the parietal lobe and hippocampus were also noted and gliomatosis cerebri growth pattern was subsequently confirmed on histopathology

FIGURE 5

Kaplan‐Meier survival curve for definitively and palliatively treated dogs with intracranial glioma that survived >1 day (n = 45). Dogs receiving definitive treatment survived significantly longer (P = .03) than did dogs with palliative treatment. Survival time represents the time from diagnosis to death or euthanasia. Shadow areas represent 95% confidence intervals

FIGURE 6

Transverse T2‐weighted magnetic resonance (MR) image of a left temporal lobe high‐grade oligodendroglioma (arrowheads) with poorly defined margins and heterogeneously hyperintense signal extending to the parietal lobe and invading the adjacent lateral ventricle (A). Transverse T1‐weighted postcontrast image at the same level demonstrating moderate non‐uniform contrast enhancement of the parietal portion of the tumor (arrow) (B). Transverse T1‐weighted postcontrast image of the same dog demonstrating a contrast‐enhancing drop metastasis in the right cerebellum (arrowhead), just dorsal to the lateral aperture of the fourth ventricle (C)