I'm curious and you don't have to tell me if you'd rather not to but where is that tumor located?
Also personally I never see doctors so they can't give me bad news, but that's just me.
I also have OCD and I loathe going to hospitals and seeing doctors. First they cost way too much money for my taste and second, they always find a way to make you take some kind of painful tests that make me totally uncomfortable. And that's when they don't want to cut you open through some surgical operation. I don't think getting cut open is natural or even something you are supposed to want.
I've never undergone surgery and I'm fine despite a doctor telling me that I must be operated cause of gall stones that hurt me bad a long time ago. When he told me that, I told him, I'm sorry but the person that it going to cut me open isn't born yet. So in short he was like: If you don't get operated you can't eat normally anymore as most foods contain fat that will hurt you really bad and also you could die if a fragment of one of those stones gets into, I don't remember where inside my body...
Well that was some 20 years ago and I'm alive and kicking, eating anything I want and haven't felt any pain again.
I won't say that doctors don't know what they're talking about but I'll say they love to get you spending money in tests and operations that make them cash in a little too easily in my opinion. I believe the human body is more resilient than people give it credit for.