Neuropathology of Canine Hemangioblastoma

Hemangioblastoma is a benign, slow-growing, highly vascular human neoplasm (WHO grade I). The tumor most commonly arises in the cerebral hemispheres and cerebellum, where it is more frequently observed in patients with von Hippel-Lindau disease. Only 7.5 to 25% of all hemangioblastomas occur in the spinal cord, and cases of extraneural localization are exceedingly rare. In veterinary medicine, hemangioblastoma has only been described in the central nervous system of dogs and in the skin of a lamb. Cases of canine hemangioblastoma have been reported in the spinal cord (5 cases), forebrain (1 case), and brainstem (1 case). Dogs treated surgically had a good prognosis. Our study aimed to characterize the neuropathological features of 6 cases of canine spinal cord hemangioblastoma and one case of sciatic nerve localization. The dogs were 4 males and 3 females aged between 6 and 12 years. The histological staining panel included H&E, Luxol Fast Blue, and Goldner trichrome staining; immunohistochemistry included the following markers: NSE, VIM, factor-VIII, GFAP, inhibin-α, carbonic anhydrase IX (CAIX), and Ki67. The tumor was composed of numerous, haphazardly arranged capillaries lined by plump endothelium and interstitial fusiform to stellate stromal cells with slightly eosinophilic cytoplasm, occasionally containing small lipid vacuoles. Mitotic activity was low. Frequently, surrounding the capillaries were moderate to prominent perivascular aggregates composed of plasma cells and fewer lymphocytes. Immunohistochemically, the stromal cells were strongly immunolabeled with NSE and were negative for factor-VIII in all cases. Inhibin-α was negative, whereas stromal cells expressed CAIX in most cases. Although the predominant location of canine hemangioblastoma is the spinal cord, its morphological and immunohistochemical features are comparable to the human counterpart. This is the first report of peripheral nerve hemangioblastoma in animals.