Canine Primary Intracranial Cancer: A Clinicopathologic and Comparative Review of Glioma, Meningioma, and Choroid Plexus Tumors

Abstract

In the dog, primary intracranial neoplasia represents ~2-5% of all cancers and is especially common in certain breeds including English and French bulldogs and Boxers. The most common types of primary intracranial cancer in the dog are meningioma, glioma, and choroid plexus tumors, generally occurring in middle aged to older dogs. Much work has recently been done to understand the characteristic imaging and clinicopathologic features of these tumors. The gross and histologic landscape of these tumors in the dog compare favorably to their human counterparts with many similarities noted in histologic patterns, subtype, and grades. Data informing the underlying molecular abnormalities in the canine tumors have only begun to be unraveled, but reveal similar pathways are mutated between canine and human primary intracranial neoplasia. This review will provide an overview of the clinicopathologic features of the three most common forms of primary intracranial cancer in the dog, delve into the comparative aspects between the dog and human neoplasms, and provide an introduction to current standard of care while also highlighting novel, experimental treatments that may help bridge the gap between canine and human cancer therapies.

Keywords: canine; choroid plexus tumor; glioma; immunohistochemistry; meningioma; pathology.

Figure 1

Glioma. (A) Canine; MRI-High-Grade Oligodendroglioma. Transverse, post-contrast T1W image illustrating heterogeneously hypointense and ring-enhancing intra-axial mass in the right parieto-temporal lobes. The mass is markedly attenuating the right lateral ventricle. (B) Canine, High-Grade Oligodendroglioma. Corresponding necropsy specimen of (A) illustrating a well-demarcated mass is present in cerebral cortex causing compression of the thalamus and dilation of the lateral ventricles. (C) Canine, High-Grade Oligodendroglioma. Sheets of neoplastic oligodendrocytes embedded in a loose matrix. Hematoxylin and eosin (HE). Inset: Areas of microvascular proliferation. HE. (D) Canine, High-Grade Astrocytoma. Discrete areas of necrosis (asterisk) with pseuopalisading by neoplastic cells. HE. (E) Human, Grade II Oligodendroglioma. Abundant peri-neuronal satellitosis (secondary structure) is present in this neoplasm. HE. (F) Canine, High-Grade Oligodendroglioma. Diffuse intranuclear immunolabeling for Olig2 immunohistochemistry (IHC).

Figure 2

Meningioma. (A) Canine; MRI. Transverse, post-contrast T1W image of a well-demarcated, ring-enhancing extra-axial mass in the ventral aspect of the left frontal lobe. Mass effect is present as manifested by the falx shift to the right. (B) Canine, Meningioma. Corresponding necropsy specimen of (A) illustrating a large, multilobular, white to tan mass that invades the neuroparenchyma. Inset: subgross histologic representation of the meningioma characterized by peripheral sheets of meningothelial cells centered on a core of necrosis. Hematoxylin and eosin (HE). (C) Canine, Transitional Meningioma, Invasive. Markedly invasive whorls and clusters of neoplastic meningothelial cells. HE. (D) Canine, Transitional Meningioma. Tightly packed whorls and clusters with an associated focus of neutrophils. HE. (E) Canine, Meningothelial Meningioma. Sheets of meningothelial cells that surround blood vessels with an acellular perivascular halo. HE. (F) Human, Anaplastic Meningioma. Large area of necrosis (asterisk) with sheets of meningothelial cells with increased mitotic figures (arrows). HE.

Figure 3

Choroid plexus tumor. (A) Canine; MRI. Transverse, post-contrast T1W image demonstrating a uniformly and markedly enhancing, sharply defined mass lesion in the lateral aperture of the 4th ventricle causing compression of the overlying cerebellum. (B) Canine, choroid plexus tumor. Corresponding necropsy specimen of (A) illustrating a tan, fleshy, slightly granular neoplasm arising at the level of the lateral aperture. (C) Canine, choroid plexus tumor. Arborizing trabecular and papillary fronds lined by a single layer of choroid plexus epithelium. Hematoxylin and eosin (HE). (D) Canine, Choroid Plexus Carcinoma. Marked invasion into the underlying neuroparenchyma by tubular-like structure of choroid plexus epithelium. HE. (E) Human, Choroid Plexus Papilloma. Ribbons, cords, and papillary fronds of choroid plexus epithelium. HE. (F) Canine, Choroid Plexus Papilloma. Robust surface immunoreactivity for Kir7.1. Immunohistochemistry (IHC).