A Secretory Variant of Cerebral Meningioma with Partial Spontaneous Regression in a Cow.

A 3.5-year-old Holstein cow presented with a 2-week history of weakness, ataxia and difficulty in rising, followed by recumbency. At necropsy, a 3 × 2.5 cm tumour mass was found in the subdural area of the left parietal lobe of the cerebrum. Histopathology revealed the tumour to be a variant of secretory meningeal tumour. Immunohistochemically, all of the neoplastic cells expressed vimentin and some were immunopositive for cytokeratin. There were variably sized, scattered pseudocysts containing eosinophilic material that stained positively with Alcian blue and periodic acid-Schiff stains. The marginal zone of the tumour exhibited regressive change characterized by lymphocytic infiltration and extensive fibrotic areas enclosing large numbers of tumour cell nests in which most tumour cells were apoptotic. This tumour was considered to be a secretory variant of cerebral meningioma with partial spontaneous regression.