I saw the vet today. The woman vet was wonderful... she was so kind and adoring to The Cheat, and The Cheat was a real trooper, what with two strangers poking and prodding and feeling and weighing her. The senior vet said that he doesn't want to do anything right now, because the one on the left seems to be going away, but to keep an eye on them for a few weeks. He says that on the off chance that it's malignant, it'll be virtually inoperable because it's bilateral.
My dad acted all pissy and insensitive when he was with me, but my mom said he told her on the phone that he feels really bad because he knows how much I love and care for the rats... Baby steps, people. Baby steps.