The lump turned out in the end to be cancer and because it had taken over his throat and he could no longer eat at all, we had to put him down.
I wonder if, instead of just destroying his eardrums, someone had actually figured out that he had a growth in his throat, it might have been safely removed and he'd still be rubbing his head on my laptop while I type. We'll never know, because we were apparently dealing with less than competent people.