Histological and immunohistochemical study of 30 cases of canine meningioma.

This report describes the incidence, location and histopathological and immunohistochemical features of 30 canine meningiomas, of which 22 were intracranial, three were retrobulbar and five were located in the spinal canal. Nine types of meningioma were diagnosed: transitional (9), meningothelial (5), psammomatous (3), anaplastic (3), fibroblastic (2), angioblastic (2), papillary (2), microcystic (1) and meningiomas arising from the optic nerve (3). One of the optic nerve tumours had a granular cell component. All tumours were examined immunohistochemically with antibodies against vimentin, S100, neuron-specific enolase (NSE), cytokeratin (CK) and glial fibrillary acidic protein (GFAP). Vimentin was demonstrated in all tumours, and concentric whorls of cells showed more intense labelling than did bundles of fibroblastic cells. S100 labelling was detected in all tumours except a single angioblastic meningioma. The intensity of labelling for S100 was lower than that for vimentin, and bundles of fibroblastic cells showed particularly strong positivity. NSE labelling was highly variable, but most tumours displayed moderate positivity. CK expression was observed in five of the 30 meningiomas, and was stronger in areas of microcystic differentiation. Most of the tumours were GFAP-negative, but two fibroblastic meningiomas were strongly positive.