Eye melanomas may originate in the iris or the vascular middle layer of the eye.

Melanomas were also described in the vicinity of the eye: pigmented masses arising from melanocytes in the sclera or the connective tissue underneath the eyelids may stand out.

Melanomas may also appear on the haired skin, sole of the feet, nailbed and oral cavity, the gastro-intestinal system and transitions between mucosae and the skin (such as the lip and anus). Depending on the location melanomas have a less or more malignant behaviour.

Behavior

Iris melanoma: a discrete, dark lumpy mass emerges from the iris.

Ciliary body melanoma: appears as a dark mass in the eye that distorts the pupil and protrudes through it.

Choroidal melanoma: affects the choroids and the retina. Initially no visual abnormalities or inflammations are observed. At a later stage, the patient may experience complications such as blindness, glaucoma, retinal detachment.

For melanomas in the vicinty of the eye, sometimes local invasion of the cornea may be present, as well as increased tear flow and mild mucous membrane irritation. These injuries have so far been described as benign, but prompt medical intervention is always advisable.

Prevalence

Melanomas near the eye are mostly found in dogs as of 5-6 years of age. Melanomas in the eye are mostly found in dogs as of 7 years of age.

Breed predisposition

Melanomas near the eye are mostly seen in German Shepherds.

First and foremost, an extensive eye examination must be performed. This can consist of an examination with a slit lamp microscope, gonioscopy, tonometry, fundoscopy and/or eye ultrasound. A fine needle aspiration of the tumour can be considered for a definitive diagnosis, but carries risks of infection, inflammation and/or bleeding.

A tumour in the eye of a dog is usually carefully monitored (e.g. by regularly taking pictures of the eye to assess possible changes in the tumour’s appearance). Because most intraocular melanomas are benign and have a low risk of metastasis, eye removal is not automatically recommended. Removal of the eye can be considered in case of tumour growth and/or when complications such as increased eye pressure and inflammation occur.

The prognosis is good. Most of these tumours are benign with a minimal risk of metastasis.