Equine intraocular melanocytic neoplasia

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

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.

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).

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

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.