Could Eye Melanoma That's Been There for Years Be Malignant?

Most melanomas inside a dog's eye are benign. About 80% are the benign type, called melanocytomas, and spread outside the eye happens in only around 1 in 20 cases. Your vet is right that spread to the lymph nodes or lungs is unlikely. Fast growth makes the malignant type more likely, so slow change over two years is reassuring, but only a lab test of the removed eye can say for sure which type it is.

Even benign tumors can keep growing inside the eye and cause glaucoma, inflammation, bleeding and pain. That's why removing the eye is often recommended once a tumor is large or affecting the eye. Removal is usually curative if it's done before any spread. Many specialists also check the chest and belly with imaging beforehand, and send the eye to a pathologist afterward.

Dogs adapt very well to life with one eye, and most owners are happy with their dog's quality of life after the surgery. It's reasonable to ask your specialist what they saw that made them suspect the malignant type, and whether the eye is already painful or its pressure is raised.

See melanoma inside the eye and eye removal.

This is general information, not a diagnosis. Please follow your own vet's advice.