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Background: Intracranial meningiomas are the most common primary brain tumors in dogs. Classification of meningiomas by tumor grade and subtype has not been reported, and the value of magnetic resonance imaging (MRI) characteristics for predicting tumor subtype and grade has not been investigated.Hypothesis: Canine intracranial meningiomas are a heterogenous group of tumors with differing histological subtypes and grades. Prediction of histopathological classification is possible based on MRI characteristics.Animals: One hundred and twelve dogs with a histological diagnosis of intracranial meningioma. Methods: Retrospective observational study.Results: Meningiomas were overrepresented in the Golden Retriever and Boxer breeds with no sex predilection. The incidence of specific tumor grades was 56% benign (Grade I), 43% atypical (Grade II), and 1% malignant (Grade III). Grade I histological subtypes included meningothelial (43%), transitional (40%), microcystic (8%), psammomatous (6%), and angiomatous (3%). No statistically significant (P o .05) associations were found among tumor subtype or grade and any of the MRI features studied.Conclusions and Clinical Importance: Meningiomas in dogs differ from their counterparts in humans mainly in their higher incidence of atypical (Grade II) tumors observed. MRI characteristics do not allow for prediction of meningioma subtype or grade, emphasizing the necessity of histopathology for antemortem diagnosis. The higher incidence of atypical tumors in dogs may contribute to the poorer therapeutic response in dogs with meningiomas as compared with the response in humans with meningiomas.

Strains of Cryptococcus spp appeared to have host specificity in dogs and cats. Differences in lesion distribution between geographic locations may reflect strain differences or referral bias. Antigen assays alone may not be sufficient for diagnosis of cryptococcosis in cats and dogs.

Although histologic examination following stereotactic or surgical brain biopsy is required for definitive antemortem diagnosis of intracranial neoplasms, these tumors are often associated with magnetic resonance (MR) imaging features that warrant a presumptive or prioritized differential diagnosis. The MR imaging features of common canine central nervous system (CNS), adenohypophyseal, and metastatic intracranial neoplasms are reviewed. Characterization of neoplasms by histologic type and biological grade is based on the 2007 World Health Organization classification system for CNS tumors in humans.

Background: Choroid plexus tumors (CPTs) comprise approximately 10% of all primary brain tumors in dogs. The clinical utility of magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) analysis, or both in the presumptive diagnosis of CPTs has not been determined.Objectives: To report MRI and CSF findings in dogs with CPT and determine if there are distinguishing features that allow clinical discrimination between the tumor grades.Animals: Fifty-six client-owned dogs with naturally occurring CPT. Methods: Retrospective case series. The inclusion criterion was histologically confirmed CPT. Blinded review of cranial MRI and cisternal CSF analysis was performed.Results: Thirty-six of 56 dogs had a choroid plexus carcinoma (CPC) and 20 had a choroid plexus papilloma (CPP). Golden Retrievers were overrepresented compared with the hospital population (frequency 3.7 times that expected, confidence interval 95% 5 2.0-6.7, P o .0002). Median CSF protein concentration in CPCs (108 mg/dL, range 27-380 mg/dL) was significantly higher than in CPPs (34 mg/dL, range 32-80 mg/dL) (P 5 .002). Only dogs with CPCs had a CSF protein concentration 480 mg/dL. Cytological evidence of malignancy in CSF was seen in 7 of 15 CPCs. Only CPCs had evidence of intraventricular or subarachnoid metastases on MRI.Conclusions and Clinical Importance: MRI, CSF analysis or both can help to differentiate between CPPs and CPCs, and may provide valuable prognostic and pretreatment information.