Immunohistochemical study on spinal cord ependymal cells and ependymomas in dogs

Abstract

Spinal cord ependymoma is a glial tumor that originates from progenitor cells lining the central canal in humans. The histopathological features and origin of canine spinal cord ependymomas remain unclear because of the limited number of cases. In this study, spinal cord ependymomas in two dogs were immunohistochemically examined and compared with normal spinal cord ependymal cells in a dog. A nine-year-old Pomeranian and a nine-year-old Maltese presented with hindlimb paraplegia. Magnetic resonance imaging revealed intramedullary T2-weighted hyperintensity lesions in the thoracic spinal cord of the dogs. Histopathological examination of biopsy samples revealed that the lesions were composed of elongated, bipolar neoplastic cells arranged in pseudorosette and rosette patterns. The neoplastic cells were positive for vimentin, glial fibrillary acidic protein (GFAP), sex-determining region Y-box transcription factor (SOX) 2, SOX9, and zonula occludens-1 (ZO-1). In the control dog, spinal cord ependymal cells consisted of three cell types: cuboidal ependymal cells, tanycytes, and cerebrospinal fluid-contacting neurons, all of which were positive for SOX2, a neural stem cell (NSC) marker. Tanycytes were characterized by vimentin-positive bipolar processes and immunopositivity for SOX2, SOX9, and ZO-1, which were comparable to the features of ependymoma cells. These findings suggest that the spinal cord ependymal layer provides a niche for NSCs and that tanycytes may be the origin of canine spinal cord ependymoma. The present study suggests that vimentin, GFAP, SOX2, SOX9, and ZO-1 are useful immunohistochemical markers for the diagnosis of canine spinal cord ependymoma.