Uveal melanoma associated with Nevus of Ota in a German Shepherd dog

A 4-year-old male German Shepherd dog was presented with a 3-day history of ocular pain in the right eye. The owner reported facial skin hyperpigmentation on the right side since puppyhood, consistent with a congenital condition known as Nevus of Ota or (oculo)dermal melanocytosis. Ophthalmological examination of the right eye revealed diffuse corneal oedema, vascular scleral congestion, diffuse iris hyperpigmentation, iris bombè and dyscoria; intraocular pressure was markedly elevated (41 mmHg). Ipsilateral facial skin was diffusely hyperpigmented along ophthalmic and maxillary branch innervation. The left eye showed no abnormalities. Ultrasonography of the right eye revealed severe iris thickening. Despite medical management consisting of topical anti-inflammatory and antiglaucoma therapy, clinical signs progressively worsened over the following 4 months, and enucleation was ultimately performed; the globe was subsequently submitted for histopathological examination. Preoperative thoracic radiography and abdominal ultrasonography were declined by the owner. Histopathologically, the anterior uveal architecture was completely affected by an infiltrating neoplasia, with transscleral extension to surrounding orbital tissues. An anterior uveal mixed cell type, scarcely melanotic melanoma was diagnosed. The dog died because of suspected pulmonary metastases 2 months after enucleation. To the best of our knowledge, this is the first report of a uveal melanoma associated with the nevus of Ota in a dog.