Hemangiosarcoma of the third eyelid in a dog.

A case of hemangiosarcoma of the third eyelid in a 7-year-old Caucasian Sheepdog is reported. A voluminous red mass protruding from the free edge of the third eyelid in the right eye was present. The mass and the free edge of the third eyelid were surgically excised. On histopathologic examination the tumor was seen to infiltrate the propria of the third eyelid and was composed of neoplastic mesenchymal cells forming irregular channels containing blood. These plump cells showed moderate anisocytosis and anisokaryosis with a low mitotic index. The surgical wound healed successfully and after 9 months there had been no recurrence. To the authors’ knowledge, this is the first hemangiosarcoma of the third eyelid reported in the dog.