13-year-old, male neutered Border terrier

• A large, rounded, and homogeneously echogenic mass is located within the posterior aspect of the right vitreous chamber, measuring 1.2 cm in diameter. This mass is poorly vascularized on color Doppler interrogation.
• The right retina is detached, displaced anteriorly by the intraocular mass. Moderately echogenic fluid is located within the right vitreous chamber, surrounding the mass.
• The right lens is unremarkable, however the right iris bows anteriorly, with its medial aspects being adhered to the lens.
• The left globe is normal
• No retrobulbar lesions are identified

1. Homogeneous intra-ocular (sub-retinal) mass OD. Given that the lesion is poorly vascularized, this mass could represent a benign granuloma, hematoma, or abscess. A neoplastic process (e.g. melanoma) is just as likely.
2. Secondary retinal detachment, OD.
3. Iris bombe, OD.

See labeled image and legend below

A transpalpebral enucleation of the right eye was performed. Histopathology confirmed the presence of an intra-ocular mass, arising from the posterior uvea, consistent with a choroidal melanoma. Secondary keratitis and optic nerve degeneration associated with chronic glaucoma were also present (see supplemental information below).

Ocular tumors are rare in dogs, with the most common intraocular tumors being benign or malignant melanoma. The most common location for these tumors is within the anterior uvea, which includes the ciliary body and iris (1,2). The choroid is a vascular tissue that resides between the retina and sclera within the optic fundus. Primary choroidal melanoma is less common (previous studies documenting 4% of diagnosed patients). Similar to human cases, most are benign in dogs (to be contrasted with ocular tumors in cats).

Surgical removal (enucleation) is controversial with patients with normal ocular pressure and no findings consistent with inflammation (2). In regards to other modalities, MRI images of melanomas are characterized by high signal intensity on T1- weighted images and low signal intensity on T2 weighted images due to the presence of melanin. Fat suppression techniques are helpful to delineate these lesions (2).

1. Penninck, D., d’Anjou, M.-A., Mellor, B., & d\’Anjou, M.-A. (2015). Atlas of small animal ultrasonography. John Wiley & Sons Incorporated.
2. Miwa, Yasutsugu, et al. “Choroidal melanoma in a dog.” Journal of veterinary medical science 67.8 (2005): 821-823.

• Chronic keratitis, with neutrophils scattered throughout the the corneal stroma
• Iris leaflets have a small numbers of lymphocytes and plasma cells
• Extending from the choroid along the posterior aspect of the vitreous chamber is a poorly demarcated mass that fills the vitreous chamber. This is composed of sheets of spindle to polygonal cells with moderate to abundant cytoplasmic melanin.
• The optic nerve demonstrates spheroids and digestion chambers (Wallerian degeneration).Microscopic Interpretation:

• Intraocular mass, posterior uvea (choroid): Melanocytic neoplasm, excised
• Mitotic count: 3 per 10 high-powered fields
• Secondary chronic keratitis, optic nerve degeneration (chronic glaucoma)

Additional ultrasonographic findings not confirmed histologically:

• The iris bombe and retinal detachment were not observed histologically as the iris and retina were incompletely included in the examined biopsy sections.