Benign intraocular teratoid medulloepithelioma causing glaucoma in an 11-year-old Arabian mare.

The research paper investigates the case of an 11-year-old Arabian mare with a benign intraocular teratoid medulloepithelioma, a rare eye tumor originating from the ciliary body and iris, causing secondary glaucoma. The study, through treatment and detailed pathological examination, provides the first report and characterization of such a tumor in an adult horse.

Background and Clinical Presentation

• An 11-year-old Arabian mare was brought in for examination due to a visible, pale-colored intraocular mass in its right eye. The mass was suspected to be contributing to a condition known as secondary glaucoma.
• The intraocular mass was confirmed through clinical examinations and ultrasonography, revealing origination from the superior temporal quadrant of the ciliary body and iris. The mass had spread to the majority of the vitreous chamber and extended into the anterior chamber.
• The horse’s left eye did not show any abnormalities and was deemed normal.

Therapeutic Action and Histopathological Findings

• The recommended course of action for treating this particular case was enucleation, a surgical process meant for both therapeutic and diagnostic purposes. No additional treatment was provided.
• Following enucleation, a histopathological examination of the eye was conducted. The examination established the intraocular mass as a benign teratoid medulloepithelioma located at the ciliary body.
• The examination involved immunohistochemical studies as well. Neoplastic cells showed positive reactions to certain proteins and enzymes including vimentin, S-100 protein, neuron-specific enolase (NSE), nestin. However, these tumor cells were negative for glial fibrillary acidic protein (GFAP).

Characteristics of the Neoplastic Cells

• Upon further investigation through electron microscopy, the cellular matrix consisting of abundant blood vessels surrounding the tumor cells was revealed. The tumor cells themselves displayed indented, round, or oval nuclei.
• Unique characteristics such as the presence of apoptotic bodies and cells containing different sizes and shapes of melanosomes were also noted.
• Eight years post-surgery, no recurrence of the tumor has been observed in the horse. Additionally, the eyesight in the horse’s left eye remains normal.

Conclusion

• This research paper concludes with a significant contribution towards understanding eye-related tumors in horses. In this case, a benign intraocular teratoid medulloepithelioma in an adult horse was reported and characterized in detail for the first time.
• The study emphasizes that early diagnosis, a detailed pathological examination, and timely treatment can effectively prevent vision loss and disease recurrence in horses affected by such benign eye tumors.