Unusual Psammoma Bodies in an Extracranial Syncytial Meningioma from a Dog

Abstract

An epidural neoplasm was removed from the right side of the third cervical vertebra of a Blue Tick Hound dog. By light microscopy the tumor was classified as a syncytial meningioma containing psammoma bodies that were histochemically positive for calcium salts, but negative for reticulum fibers and collagen. Ultrastructurally, the tumor cells had numerous processes and desmosomes. Cytoplasmic fibrils were sparse. Coated cytoplasmic vesicles frequently were fused with plasma membranes. The psammoma bodies were not within the cytoplasm, but were in spaces continous with the extracellular space. The bodies were composed of a medium electron-dense matrix; a crystalline, highly electron-dense center; and, sometimes, short fibrils embedded in the granular matrix.