Lumps on mammary glands.

Fraya is a rescue we have had for a month. We are not sure of her age, but we think she is 8-10 years old. She was rescued from a breeder and was spayed about a month and a half ago. Last week on Monday we noticed an odd shaped form on her belly by one of her nipples. I mad an appointment for her to see the vet on Friday. By the time of the appointment she had several odd shaped hard lumps all along her left mammary chain and a round lump on her one of her right nipples. The vet wants to do surgery and remove the entire left mammary chain and the lump on the right. We will do xrays before the surgery. Our concern is that more of the hard odd shaped spots are appearing on her. She now has them along her her belly under her spay site and 2 on her right side. She has also developed another round small mass under another nipple on her right side. I am concered with how fast this is all spreading and was curious with out having bloodwork what your opinion of this is. The doctor wants to remove the right side when Fraya heals from the first on her left. My concern is that since it seems to be speading rapidly (within 1 to 1 1/2 weeks) that it may be a very aggressive cancer that is hard to treat. Since we can not remove both mammary chains at once, waiting for her to recover to remove the other side seems like she will be riddle with the cancer by that time. Have you seen cancer spread this fast and what options are there? We want to help but are also not sure of the finacial part of all this as it seems to be rather expensive for the surgery. Any help you can give we be wonderful. How long can a dog live with treatment with this kind of cancer? Thanks.

I just wanted to give you an update about Fraya. After consulting more with our vet on monday, he felt that while this was an aggressive cancer we caught it early enough. The bumps under her spay site were from the spay, we just had not noticed them before. We did the surgery on wednesday and she is doing wonderful. We are havng a hard time keeping her quite. The doctor removed the entire right mammary chain and little Fraya doesn't seem to know anything happened. Thanks for your help and input on this.