Hemangiosarcoma of the third eyelid in a horse

A 12-year-old Belgian Warmblood mare was referred to the equine clinic of the Faculty of Veterinary Medicine (Ghent University) for a mass on the third eyelid of the right eye. The horse had been having a recurrent red-tinged ocular discharge for several months. After complete ophthalmologic examination, a large part of the third eyelid was surgically excised and submitted for histopathologic examination. The histopathologic examination revealed a proliferation of blood-filled vascular spaces lined by a single layer of flattened cells, which were identified as endothelial cells using immunohistochemistry. The tumor was identified as a cavernous low-grade hemangiosarcoma. No complications were reported six months after surgery