Choroidal melanocytic tumors in dogs: A retrospective study.

Objective: To describe clinical features of dogs diagnosed with choroidal melanocytic tumors at a veterinary teaching hospital.

Animals Studied: Retrospective case series of 13 dogs (14 melanocytic tumors) with choroidal melanocytic tumors.

Procedures: Medical records of dogs evaluated by the Cornell University ophthalmology service with a clinical diagnosis of a choroidal melanocytic tumor between 2008 and 2020 were reviewed. A choroidal melanocytic tumor was clinically defined as any well-demarcated, raised pigmented choroidal lesion underlying the retina. Histopathology results were consulted when available. Signalment and clinical features were recorded, including fundoscopic location, histopathologic findings, treatment, and outcome.

Results: Choroidal melanocytic tumors were identified in 14 eyes of 13 dogs. The mean (±standard deviation) of dogs was 8.6 (±3.5) years. Seven different breeds were represented, with Labrador/Labrador mix being the most common. Ten of the 14 melanocytic tumors were diagnosed incidentally. Four dogs presented for vision loss and ocular discomfort, and diagnosis was made on histopathology examination following enucleation. Pulmonary metastasis was suspected in one dog with an incidentally found choroidal melanocytic tumor OD. Fundoscopic location was available for 8 melanocytic tumors, with 6 (75%) located in the tapetal fundus. Histopathologic diagnosis was melanocytoma for 3 and malignant melanoma in 1 globe, with optic nerve head invasion in 50%. Local recurrence was not seen in any orbit following enucleation.

Conclusion: Choroidal melanocytic tumors are uncommon in dogs. Metastasis appears to be rare and was only suspected in one dog, but intraocular tumor growth can lead to retinal detachment, glaucoma, and necessitate enucleation.