Yes he was, but that was because they also had to remove several mast cell tumors that had also shown up. I do think that even if it were only the growths on his penis they still would have had to put him under because they were fairly large.
On the other hand, when I first got him he had a melanoma on his butt cheek that was a lot bigger than your horse’s and a few smaller ones on his neck. The vet removed those while he was standing. They have never come back.
I wouldn’t ignore the one on his butt cheek. It sounds small enough that the vet could remove it under sedation. That might be the end of it. If the ones elsewhere are stable I don’t think I would have them removed. My horse still has lumps under his tail and on his penis but they are out of the way and are growing very slowly if at all.
Especially given our horses’ ages, I don’t think it is realistic to think that we can make them completely bump free. Genetics are powerful! But we do now have tools to keep the worst of it at bay.
Whatever you choose, I hope it all works out well for you and the horse. Keep us posted!
