Hemangiosarcoma and squamous cell carcinoma in the third eyelid of a horse.

This research details a rare case of a horse diagnosed with both hemangiosarcoma and squamous cell carcinoma in its third eyelid, which could not be distinguished without histopathology. Despite surgical intervention, the horse developed recurrence and metastasis, leading to euthanasia.

Presentation and Initial Diagnosis

• The subject of the study was a 12-year-old Belgian draft horse. It was brought to the attention of the researchers due to a mass in the right eye’s third eyelid. The mass had been present for about three months and was accompanied by a red-tinged ocular discharge.
• The third eyelid was surgically removed and sent for histopathology, which is the study of changes in tissues caused by disease.

Histopathological Findings

• Upon histopathologic examination, it was revealed that the mass was not a single type of tumor but a combination of two separate neoplastic processes, namely hemangiosarcoma and squamous cell carcinoma.
• These two kinds of cancers are quite different. Hemangiosarcoma is a form of cancer that primarily affects blood vessels, while squamous cell carcinoma affects the squamous cells, which form the majority of the horse’s skin surface.
• These tumorous components within the same mass were impossible to differentiate grossly, or by visual inspection alone, making this case unusual.

Post-Surgery Developments and Outcome

• About 16 months after the surgical removal of the mass, the horse exhibited thickened eyelids and hemorrhagic ocular discharge from the right eye. These symptoms indicated the resurgence of the disease, prompting the decision to euthanize the horse.
• Postmortem examination and histopathology confirmed that the hemangiosarcoma had not only recurred locally, but it had also metastasized regionally. This means the cancer had spread from the initial location to nearby tissues or lymph nodes.