That is a tough one Ralph. Not sure what kind of blood tests were run. If they were run checking for cancer markers or just for standard liver, kidney, and other such labs. When the doctor says the blood work came out all okay, what does that mean exactly?  What checked out okay?  If it is solid and not caused from an abscess then it could very well be a type of tumor. But keep in mind tumors are not necessarily malignant. It could be benign. 12 years! Congratulations to you both. But that is getting up there. In being honest with you I had a relatively unnoticeable flat mole on my eyelid all of my life that all of a sudden in my late late 40’s decided to grow like crazy in a very short period of time. Of course I thought the worst but it was benign. Benign can still be a fast growing structure.  And it was. I had it removed and I am no worse for the wear.

All that to say it seems like a growth. The growth could be malignant or benign. And both types of growth can be aggressive. So I would want to know specifically what tests were run on the blood. What was checked? So if I were you I would ask more specific questions. Since it is seems more superficial, large, and easily accessible why wouldn’t the vet do a biopsy to check? Again I am not a vet. Just some questions I am throwing out.

The one big caveat of this whole deal of course is the age of your bunny. Undergoing anesthesia at any age has risks but obviously the older a bunny the more the risks. So that is definitely a concern. So (this is just me – again not a vet) I would want to have a better diagnosis of what that lump is before going through the risk of anesthesia. It may very well be that is the only course of action after all. But I would want to exhaust all avenues of diagnosis before taking that chance. I would also think that if they did do the surgery to remove it then they would send it in to be checked for malignancy as well. But me being me, again I would exhaust all avenues of diagnosis before any major surgery. Whatever questions you have in the back of your mind, present those questions to the doctor. Even if you think those questions may be stupid. Get your questions answered. All of them. Make sure you understand the answers fully. You need to feel as comfortable and confident as you can with whatever direction you choose to go with the care of your bunny. Keep us posted.

I agree with Gordo and Janice, the best test that needs to be run is a biopsy or an aspiration( needle proding it and putting it on a slide and looking at it under a microscope and see what cells it is. That will tell you what treatment can or can’t be done. Congrats on 12 years!