I would speak at length with the vet. He really should not have to be anesthetized very long to have that thing removed. Just be sure to have labs drawn prior to make sure there is not a problem where anesthesia could be an issue. Usually with the older pups, they give them IV fluids.
I would definitely get it removed if it were my pup. My George who is approximately 12 (could be older..he was a rescue) just had a dental a few months ago and had some growths removed at the same time. As he has gotten older, he has started to develop them and I have her remove them during his dentals so that there is not an extra procedure. The risk of a pup dying from anesthesia is very, very low. We always have to balance risks...what if you leave that growth? It could become much worse. As I said, best to have a discussion with your vet.
Please keep us posted. He is a cutie.
