Solitary (primary) uveal T-cell lymphoma in a horse.

This research paper presents a unique case of a horse diagnosed with a rare form of eye cancer, specifically, a primary solitary uveal T-cell lymphoma. The study suggests not overlooking the possibility of lymphoma in horses with uveitis, even if the inflammation is one-sided, and no other signs of cancer are present.

Introduction and Presentation of the Case

• The study revolves around a 22-year-old Australian stockhorse gelding that showed symptoms of anterior uveitis (a form of eye inflammation) in the right eye, unresponsive to anti-inflammatory treatments.
• Upon examination, professionals observed corneal edema (swelling), vascularization (formation of blood vessels), severe hypopyon (a medical condition where there is pus in the human eye, typically, the anterior chamber), and thickening of the dorsal iris, which was later confirmed by an ultrasound.

Investigation and Diagnostic Process

• To identify any underlying cause, hematologic and biochemical analyses were conducted, alongside abdominal and thoracic ultrasonography, abdominocentesis, and biochemical analysis; however, no significant abnormalities were determined.
• A cytological examination of an aqueous humor sample (a thin, transparent fluid in the eye) was performed, which revealed the existence of large lymphoblasts (immature cells that create lymphocytes), thereby indicating intraocular lymphoma (eye cancer).
• A biopsy of the right submandibular lymph node (situated beneath the mandible) revealed no evidence of cancer invasion.

Results and Conclusion

• The horse was euthanized and a full necropsy was conducted, which revealed no existence of cancerous tissues, except for in the right eye.
• The eye contained extensive, well-defined infiltrates of cancerous lymphocytes, affecting areas such as the ciliary body, iris, ciliary epithelium, pars plana, and peripheral choroid.
• Immunohistochemistry tests confirmed that the cancerous cells were expressing the T-cell marker CD3, thus diagnosing the horse with a primary solitary uveal T-cell lymphoma.
• To the authors’ knowledge, it is the first recorded encounter of such a disease in a horse, thereby making the paper a focal point of new understanding and further studies about uveitis related ailments in horses.
• The study concludes that lymphoma should also be considered in horses showing symptoms of uveitis, even if it’s unilateral or in the absence of any extraocular signs of cancer.