Primary leptomeningeal gliomatosis in a domestic shorthaired cat.

A 15-y-old neutered male domestic shorthaired cat was presented with a 16-d history of hindlimb paralysis in conjunction with 1-wk duration of inappetence and lethargy. Given intractable clinical signs, development of seizures, and poor prognosis, euthanasia was elected. Gross examination revealed mild, chronic, multifocal intervertebral disk disease; however, no gross abnormalities were noted in the spinal cord. Histologic examination of the cervical, thoracic, and lumbar spinal cord and the myelencephalon revealed diffuse and variable expansion of the meninges by sheets of neoplastic round-to-polygonal cells. The cells formed sheets and clusters, supported by a variably eosinophilic, fibrillar-to-basophilic, homogeneous matrix, and contained a small amount of eosinophilic cytoplasm. The nuclei were round with finely stippled to hyperchromatic chromatin and 1-2 small nucleoli. Mild white matter degeneration was present in the dorsal and ventral funiculi multifocally throughout the spinal cord, but was most severe in the ventral lumbar sections. Immunohistochemistry revealed strong intranuclear immunoreactivity for Olig2, and intracytoplasmic immunoreactivity for glial fibrillary acidic protein, MAP2, and vimentin in the neoplastic glial cells. To our knowledge, primary leptomeningeal gliomatosis has not been reported previously in a cat.