My rabbit has had mastocytoma for quite a few years. Quite large on his side. His eating and pooping habits are normal. He seems to have chewed off some of the mass, as he is a fistey little guy and it was impeding his movement. He is neutered, of course. I am not wanting to get into surgery on this as we have already gone through this with a cat and it only led to an add'l year on his life. He is an inside rabbit, given the best food and hygenic care. Any suggestions - Is he in pain?