Oh my gosh, poor little guy! Please, let me know if there's anything I can do. I remember you mentioning a tumor boy to me when I was first looking to add to my group. If nothing else, at least the lady cared enough to to hand them over to the rescue. Did you contact her and suggest it to her or did she find it on her own?
If that Cheerio picture is any indication, at least the tumor itself seems pretty mobile if he can get his arms up over it, which should be a good sign. How do they seem otherwise, healthy?