Cerebral angioendotheliomatosis in a dog.

A 6-year-old dog which presented with weakness of the hind limbs progressed to a cerebral disorder with altered sensorium. The cerebrospinal fluid (CSF) protein was elevated, but no cells were found. Autopsy revealed severe hemorrhages in the basal nuclei and diencephalon. Histology of the lesions showed many meningeal and parenchymal blood vessels filled with neoplastic mononuclear cells. Electron microscopy of the tumor cells demonstrated ribosomes, granular endoplasmic reticulum, mitochondria, and a few lysosomes. Immunocytochemical procedures to demonstrate Factor VIII-related antigen were negative. This appears to be the first recorded case of cerebral angioendotheliomatosis in domestic animals and closely resembles the syndrome in man.