Just heard back from Buster's vet—the growth they removed from his nose is completely benign, and they were able to excise all of it. Poor guy is stuck in the cone of shame for another week until he gets his stitches out, but then he's entirely in the clear.
So happy and relieved! I just don't know how I'd cope if I lost him—I've never been anywhere near as bonded with a pet as I am with him, and I just can't imagine my life with him following me everywhere wagging his tail, snuggling up with me whenever I lie down, and shooting me pointed looks to let me know exactly how silly he thinks I am (I swear to god he got sarcastic with me the other day. It was amazing!).
Yay for healthy puppies!