Secondary infections can
occur as the consequence of tumors, but even an abcess can recur. So if it doesn't heal, the vet would likely want to remove it, even if it isn't
cancerous. Sometimes dogs develop cysts that will keep reinfecting and not heal--since any infection can be dangerous, it's often necessary to remove them to get rid of them.
that your dog's abcess heals up on its own and doesn't recur!