These large iris masses are highly likely to be neoplastic. It is conceivable that they could be metastases from a distant neoplasm such as a mammary carcinoma but lymphoma is the top of my differentials list. In fact as you can see here there were smaller lesions in the iris of the other eye and cutaneous masses too. They didn’t look anything like as spectacular as the eye signs to me (or maybe that’s just an ophthalmologist’s biased perspective!) but if you wanted to have a look at one of them send me an e-mail by clicking on the button on the homepage and I’d be happy to send you a jpeg of a fairly non-descript skin mass! Incidentally the cat was FeLV/FIV negative. The COP protocol was effective in resolving the iris lesions but obviously not the generalised disease as on cessation of treatment the iridal lesions recurred and a more aggressive regime including doxyrubicin has been initiated.