Presumed primary ocular lymphangiosarcoma with metastasis in a miniature horse.

An American Miniature mare was diagnosed with primary ocular lymphangiosarcoma, a rare and aggressive cancer, that eventually metastasized, leading to its euthanasia.

Case Overview

• The subject of the research was a 7-year-old American Miniature mare weighing 153.0 kgs. The horse was brought in due to a case of keratoconjunctivitis in its right eye.
• The initial diagnosis revealed a conjunctival mass (a lump at the edge of the cornea) and stromal keratitis (an inflammatory condition) in the right eye.
• An incisional biopsy was performed, which identified a corneal hemangiosarcoma – a vascular tumor arising from the blood vessels of the cornea.

Post-Biopsy Actions and Findings

• Following the biopsy, enucleation – removal of the eye while leaving the eye muscles and contents in the orbit intact – was performed to manage the tumor.
• However, despite the surgery, the horse developed complications like progressive epistasis (nose bleeds) and orbital swelling (eye socket swelling).

Late-Stage Diagnosis

• Three months after enucleation, the horse was examined again, which showed regrowth of the tumor in the orbit and significant lymphomegaly (enlarged lymph nodes) in the cranial cervical region, suggesting metastasis, or spread of the original cancer.
• Equine euthanasia was ultimately carried out as a more humane alternative given the condition of the horse. A necropsy post-euthanasia confirmed aggressive tumor spread to submandibular tissue (below the jaw), the submandibular lymph node, and the thoracic inlet (the opening at the top of the chest).
• Upon further histopathologic examination, findings were consistent with lymphangiosarcoma, as the neoplastic cells lined the vascular channels devoid of erythrocytes (red blood cells).
• The immune-marking (immunohistochemical) profile of these cells, being strongly positive for PROX-1, vimentin, CD-31, and VEGF, with a weak positive for factor VIII-associated antigen, further supported the final diagnosis of primary ocular lymphangiosarcoma, a cancer of the lymphatic vessels, that metastasized.