Feline glioma: a retrospective study and review of the literature.

Case series summary This study aimed to evaluate the pathologic and diagnostic features of 13 cases of feline glioma diagnosed at two veterinary diagnostic institutions over 16 years. A retrospective search was conducted using the laboratory information system. Selected cases were reviewed, tumors were classified according to the 2007 World Health Organization Classification of Tumours of the Central Nervous System, and tissue sections were submitted to an immunohistochemistry panel for further characterization. Affected cats were adults (average age 8 years), and male neutered (9/13) domestic shorthair cats (12/13) were over-represented. Clinical signs had acute onset and were progressive, lasting from 1-60 days (average course 20.7 days). Euthanasia was elected in all but one case, owing to a poor prognosis or because of a suspicion of rabies. Tumors occurred in the telencephalon (8/13), spinal cord (3/13) and brainstem (2/13). Gross changes in seven cases consisted of well- or poorly demarcated, gray-to-brown, soft, gelatinous masses that often caused secondary changes to the brain. The final diagnosis and classification were made based on histopathology and immunohistochemistry. Diagnoses consisted of oligodendroglioma (six cases), anaplastic astrocytoma (two cases), oligoastrocytoma, anaplastic ependymoma, gliomatosis cerebri, glioblastoma and anaplastic oligodendroglioma (one case each). Relevance and novel information This article confirms the need for a full neurologic and neuropathologic examination in cats with clinical neurologic disease. In addition, it highlights and proposes a complete routine immunohistochemical panel for diagnostic confirmation and differentiation between glioma and other morphologically similar central nervous system neoplasms in cats.