Equine intraocular melanocytic neoplasia.

Objective: To describe the clinical appearance, histopathology, and treatment of equine intraocular melanocytic neoplasia in adult horses.

Animals and procedure: A retrospective review of medical records was conducted. Data recorded included signalment, ocular examination findings, physical examination findings, therapeutic interventions, and case outcomes. Histopathologic characteristics of enucleated globes were evaluated. A Student's t-test was used to evaluate differences in the interval from diagnosis to last known outcome between horses receiving therapeutic interventions and horses undergoing monitoring alone.

Results: Of the 55 horses included, Arabian was the most common breed (15/55, 27%). Gray was the most common coat color (85%). Physical examination was completed for 75% of horses at time of diagnosis, and of those, 67% had cutaneous melanoma. The interval from diagnosis to last known outcome was not different (P = 0.312) between horses that underwent monitoring alone (median: 2.0 y) and those that received treatment (mean: 2.25 y).

Conclusion: Equine intraocular melanocytic neoplasms are highly associated with cutaneous melanoma and gray coat color, and they are more prevalent than previously published reports suggest.

Clinical relevance: A complete ophthalmic examination is indicated for all horses with cutaneous melanoma. Additional research into the timing and rationale for treatment of intraocular melanocytic neoplasia is necessary.