Meningioma in the fourth ventricle in 2 cats.

Feline meningiomas typically arise on the surface of the brain but can occur in the third ventricle. Meningiomas in the fourth ventricle have not been reported in cats, to our knowledge. Here, we describe the clinical and pathologic findings of meningioma in the fourth ventricle in 2 cats. Both affected patients (1 castrated male, 1 spayed female) were 15-y-old. Case 2 had neurologic signs, including absent menace response, head tilt, and ataxia. Grossly, both tumors were well-demarcated and firm, expanded the fourth ventricle, and compressed the adjacent neuroparenchyma. Cytology of the ventricular mass in case 1 revealed a spindle-cell neoplasm. Based on histology, the neoplasms were classified as WHO grade 1 fibrous meningioma (case 1) and transitional meningioma (case 2). Immunohistochemistry revealed diffuse, robust cytoplasmic E-cadherin and vimentin immunolabeling in both cases and multifocal, weak cytoplasmic pan-cytokeratin AE1/AE3 immunolabeling in case 2. Our findings indicate that meningiomas should be included as a differential diagnosis for tumors of the fourth ventricle in cats.