Cat Eye Tumors: Seventy-five percent of feline eye tumors in cats are malignant, aggressive forms of cancer (in dogs the ratio is reversed, 75 percent of tumors are benign and do not spread or become life-threatening).
An Iris melanoma is the most common type of tumor affecting cat’s eyes. Older cats may develop a visible brown or black spot on the iris of their eye.
The Iris is the colored part of the eye. The spots may be single or multiple and are pigmented cells called Melanocytes that have overgrown. Examination involves the use of a slit-lamp bio-microscope, which determines whether or not the tumor is cancerous. If the pigmented area on the iris is flat, the lesion is referred to as Iris Melanosis. This is considered to be pre-cancerous and should be rechecked at six-month intervals.