Angiosarcomas arising in ocular tissues of four aging horses are described. Tumors were locally invasive and eventually metastasized via the mandibular and cervical lymph nodes. Pathologically, the tumors contained well-differentiated regions, in which vascular channels were lined by pleomorphic endothelial cells, as well as poorly-differentiated regions, in which vascular channels were either rudimentary or absent. Red blood cells were scarce in vascular structures formed by the tumors. Factor VIII related antigen (VIII:RAg), a blood vascular endothelial marker, was demonstrated by immunohistochemistry in tumor cells in both the well-differentiated and poorly-differentiated regions. The results suggest that ocular tumors arose in blood vascular endothelium and represented true hemangiosarcomas although a lymphatic endothelial origin could not be excluded. Immunohistochemical demonstration of VIII:RAg is a valuable adjunct to conventional stains in the diagnosis of equine vascular neoplasia.
ASJC Scopus subject areas