Meningothelial meningioma in a Malayan sun bear (Helarctos malayanus)

Abstract

A 24-year-old, spayed female Malayan sun bear ( Helarctos malayanus) in the Taipei Zoo (Taipei, Taiwan) showed clinical signs of slowly progressive anorexia, dullness, compulsive pacing, and circling. The animal subsequently developed acute severe stupor and persistent recumbency. Postcontrast study of computed tomography revealed a spheroid, extra-axial mass with strong but heterogeneous hyperattenuation in the left temporal lobe of the cerebrum. At necropsy, a solitary, well-circumscribed intracranial mass measuring 3 cm × 2.5 cm × 2 cm was attached to the left pyriform lobe with compression of the adjacent neuroparenchyma. Cytological examination obtained from the mass revealed large clumps and sheets of cohesive polyhedral cells with round nuclei, wispy cytoplasm, and indistinct cell borders. Microscopically, the mass was composed of densely packed round to polygonal cells arranged in lobules and small nests. Psammoma bodies, xanthomatous change, and cholesterol deposition were also noted. Immunohistochemical staining of the tumor was positive for vimentin, pancytokeratin, cytokeratin (CK)34BE12, neuron-specific enolase, and epithelial membrane antigen, but negative for glial fibrillary acidic protein and S100 protein. The cytological, histological, and immunohistochemical features were compatible with a meningothelial meningioma.