My Dog Has a Breast Tumor (Experience? Advice? Thoughts?)

So, about a week or two ago, we noticed that my chihuahua had this growth of sorts on her stomach. It was right where one of her...teets?...should be, and it's purplish in color and just really weird looking. We'd initially decided to wait and see if it would go away, but it hasn't, so today we took her to the vet.

Well, we just got back, and the vet informed us that Sasha has a breast tumor. They're going to operate on her to removed it on October 31st, and then send the tumor away to be tested to see if it's a "good" tumor or a "bad" tumor.

I really have no experience with this type of thing, so I was wondering if anyone on here has dealt with a situation like this with their dog. If some of you have, can you fill me in on what went on and the overall outcome? Whether it's bad or good, I really just want to know what I can expect. I know every dog is different, but if I could just hear some first-hand accounts, it may make me feel less worried and anxious.

If you have a few moments, please head over to the comment section and let me know! It would be much appreciated.

xoxo.