I'm happy to say the vet called this evening and the news is all good.
Mabel's little growths were benign and once she has her stitches out
next week everything should be a-okay. (The bright purple stitches are
hiding on the back of her neck--conveniently out of her reach. Thus no
need for a kitty cone :-)
Mabel is now paying forward her good kitty karma to her kitten pal Otis, who has a lump of his own.