Extraneuraxial Canine Meningioma

A tumor mass removed from the subcutaneous tissue of the shoulder of a dog had the light and electron microscopic features of extraneuraxial meningioma. The neoplasm probably arose from arachnoid cap cells displaced during embryogenesis. Although intracranial canine meningiomas are common [ 141 no primary meningioma, to our knowledge, has been reported outside the central nervous system in dogs or other animal species. Extraneuraxial meningiomas occur occasionally in man and are predominantly in the head and neck area [13]. We are aware of only one such neoplasm in man in which the meningiomatous nature of the lesion was confirmed by electron microscopy [13]. There is no similar ultrastructural study in the veterinary literature.