tumor? abscess?

You guys are not going to believe this but now I think Maggie is developing
a tumor! I noticed it this week and thought maybe it was the way her skin
was folding (she's hairless so she has a lot of skin folds). Over the past
two days the mass has grown. It's about the size of a small pea, flatish,
but not hard at ALL, very squishy and white just under her skin. It's under
her right armpit. It moves with the skin.

I've been reading Debbie Ducommon's Rat Health Book, but I can't figure out
if it's the beginning of a mammary tumor or an abscess. She's about 11
months old.

Of course, Maggie will be seeing a vet next week, but the issue is that even
the vet I found which is an hour and a half away does not do rat surgery.
So if it is a tumor, who knows - I guess I'll have to go to another state!
I'd just like to know if anyone can give me an idea of what I might be
dealing with here, and if she might end up needing surgery.

The good news is Jacques is making a major comeback from his near-death
myco/infection last week. Now if I could only keep all 3 healthy at the
same time.

Meghan