Tumor, cancer & pockets of milk

Mizzy has a mammary tumor and a large pocket of milk growing on her lower abdomen. Actually, the vet said it's many small pockets of milk, which is why we can't drain it with a syringe, and that there are cancer cells. Has anyone dealt with this before? If so, how did you treat it? We have her on bromo and pred, hoping the bromo would stop milk production, but it's still growing. It's almost to the point where tough decisions will have to be made. I'm thinking about asking if we can try tamoxifen. I think she feels pretty crappy on her current meds, though she may just be feeling horrible from the cancer/pouch. I hate to add another med and make her feel worse if there's no hope. I'm also wondering if I should stop the bromo if she's still producing milk anyway after several weeks on it.

What do you guys think?

Edit: I've decided to go ahead with the tamoxifen. Now I just need to decide whether or not to discontinue the bromo. I've read that bromo can reduce prolactin levels from the pituitary gland, but it has no effect on prolactin created in other parts of the body, including mammary tissue. So, is the overall reduction in prolactin beneficial, or is the bromo pointless? I'm thinking it's pointless, but tamoxifen looks at least somewhat promising.

"The local production of prolactin cannot be controlled by conventional dopamine agonists that act at the pituitary level. This failure of bromocriptine (the most commonly used dopamine agonist in cancer studies) to reduce local PRL levels resulted in the failure of this drug in cancer studies.
...

Recent research has indicated significant interaction between estrogen and prolactin systems. Estrogen stimulates prolactin secretion and can also up-regulate human prolactin receptor gene expression and stimulate growth of tumorigenesis.[8] Prolactin has been shown to exert some of its effects on mammary tumor cells via the estrogen receptor. Anti-estrogens like tamoxifen have also been found to block the prolactin receptors. This could represent another pathway of cancer therapy, discrete from the anti-estrogenic effects of these drugs."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3603025/

We've had mammary tumours removed which contained milk and that seemed to be the end of it. The rat lived just fine after removal.

We had a large one that was filled with milk removed from Mizzy a couple of months ago, and almost immediately after, her abdomen started filling up with what we thought was fluid. It turned out to be a bunch of little pockets of milk and cancer cells under the skin. I'm not sure how or why she formed all of these pockets, and I can't find any other instances of it online. She also has several small tumors under the pouch of milk and in other spots. Surgery isn't really an option.

We discontinued the bromo and started tamoxifen. I debated a lot on the tamoxifen because of how toxic it is, mostly for the sake of the two boys she lives with, but I couldn't let her go without trying.

I've heard of a lot of people using Tamoxifen with success.