Choroid plexus tumors in 56 dogs (1985-2007).

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%= 2.0-6.7, P < .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 = .002). Only dogs with CPCs had a CSF protein concentration > 80 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.