Intracranial Transitional Meningioma in a Cat

Background: Meningioma is a tumor that is usually attached to the dura mater. It typically arises from the meningothelial cell of the arachnoid or pia mater. Considered an extra-axial tumor of the central nervous system which can occur on any region of the meninges. The biological behavior tends to be benign and usually is not infiltrative allowing surgical indication, conferring to the patient a better prognosis. Geriatric patients are the most affected and there is no breed predisposition. This paper describes the clinical signs, pathological findings, and immunohistochemical features of a case of transitional meningioma in a cat.Case: A 14-year-old, neutered male mongrel cat was referred to the Veterinary Clinic Hospital. The history was that the cat had anorexia and disorientation. On the day of admission, lethargy and blindness were observed. Full complete blood counts showed leukopenia and lymphopenia. The serum biochemistry tests were unspecific. Thoracic and skull radiographs and ultrasound examination revealed no abnormalities. The cat was hospitalized and the main treatment was based on antibiotics and corticosteroids. The cat tested negative for FIV and FeLV. Toxoplasma gondii serum antibodies were not detected using indirect fluorescent antibody test performed with a commercial kit. The clinical signs progressed to walking in circles, stumbling, wandering, anisocoria, and stupor. On the eleventh day the cat died during hospitalization. The cat was submitted for routine post-mortem examination revealing a rounded mass involving the right occipital cortex and the cerebellum, easily separable from the brain parenchyma. In the brainstem there were moderate diffuse congestion, perivascular edema, and moderate multifocal areas of necrosis, and hemorrhage. Histological examination revealed neoplastic cells sit in tight little whorled clusters, sometimes elongated with abundant collagen intermingled. Sections from the tumor underwent immunohistochemical evaluation for glial fibrillary acidic protein (GFAP), S100, cytokeratin, and vimentin. There was immunoexpression only of vimentin. The diagnosis of transitional meningioma was established from the pathologic features and confirmed by positive staining of vimentin antibody.Discussion: The animals affected by brain tumors present a series of poorly defined or mild neurological signs. Unfortunately, evaluation of cerebrospinal fluid is neither sensitive nor specific test for the diagnosis of meningiomas in dogs and cats. Computed tomography and magnetic resonance imaging are considered the main diagnostic tools available for ante-mortem investigation of several types of brain tumors, but they are also expensive and difficult to obtain in veterinary medicine. The neurosurgery related morbidity and mortality limits the biopsy and surgical treatment to veterinary centers with highly qualified and advanced anesthesia techniques and critical care. In Brazil, there is no report of transitional meningiomas in cats and there are a few controlled studies to better insight into the biological behavior of intracranial neoplasms, prognosis and therapeutic procedures in cats. The meningioma should be included in the differential diagnosis of patients with clinical signs of intracranial diseases. However, as the difficulty of performing imaging tests specific prevents the antemortem diagnosis, definitive diagnosis is restricted, in most cases, to necropsy and histopathology.Keywords: brain tumor, feline, intracranial tumor.