My last cat had eye cancer that looked like this. We watched it for years and eventually had the eye removed when it started to deform. The pathology came back benign though. My cat did perfectly fine with the surgery and was back to his normal doofy self within 2 weeks. He lived another 3 years and passed last Christmas from another unrelated cancer at a ripe old age. I'd say don't worry too much just give your buddy their best life.