Retrobulbar Fibrosarcoma in a Sheep

This report describes a case of a retrobulbar fibrosarcoma in a 4-year-old female sheep. A big tumor was protruding from the orbit but not invading the surrounding tissue and was easily removed surgically. The grayish colored mass was 19×13×8 cm in size and hard. The surface of the tumor was irregular and ulcerated. Marked hemorrhage and necrotic areas were present across the whitish cut surface. Histopathologically, the mass was composed of spindle shaped, anaplastic pleomorphic cells. Masson’s trichrome staining revealed a collagenous matrix in the tissue. Immunohistochemically, the mass was positive for vimentin and proliferating cell nuclear antigen but negative for smooth muscle actin, desmin, glial fibrilar acidic protein and S100 protein antibodies. According to histopathological and immunohistochemical findings the tumor was diagnosed as fibrosarcoma. To the authors’ knowledge, this is the first report of ocular fibrosarcoma in a sheep.