Brain tumors in small animals are relatively common, occurring at an age-standardized incidence rate of 20 cases per 100,000 dogs per year~1. In dogs, meningiomas and gliomas are most common, whereas in cats meningiomas predominate. Other primary brain tumors include choroid plexus tumors, primary CNS lymphoma or histiocytic sarcoma, and primitive neuroectodermal tumors2'3.Pituitary tumors are most often included with secondary brain tumors. Secondary brain tumors include hemangiosarcoma (especially in dogs), secondary CNS lymphoma and intravascular lymphoma, carcinomas, nasal tumors, secondary histiocytic sarcomas, and melanomas.Occasionally, the simultaneous occurrence of a meningioma with a glioma, a choroid plexus tumor or another meningioma in the same dog is reported, and while cats sporadically present with a meningioma concurrent to lymphoma or another secondary brain tumor, it is slightly more common for cats to present with 2 to 4 or even more concurrent meningiomas4'11.The outcome of dogs and cats treated for brain tumors with supportive therapy only has not been closely studied. In 45 dogs with brain tumors receiving either no treatment or supportive therapy, a median survival of only 0.2 months was reported.
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