If you have lived with a cancer cat, you know many issues can arise regarding diagnosis, treatment, and monitoring. This question and answer regarding mammary cancer illustrates some of the dilemmas facing the owner.


We have a 16 1/2 year old Siamese who had one lump removed two months ago that was cancerous. Now there is another lump that is less than 2cm. Do you reccommend a unilateral mastectomy of this one chain or just another lump removal? She has kidney issues and is fine and creatinine levels are fine but kidneys are in decline. She handled the first surgery great but is a unilateral mastectomy too much for an almost 17 year old cat?

She has no signs of problems and still plays and runs. She did very well after the lumpectomy but don't know if the mastectomy is too much. The lump was sent off and it was an adenocarcinoma. She has issues with using a litter box most days but we seem to think that is due to kidney issue instead of cancer cat symptoms. Are we correct about that?


Hi. Randy,

There is no clear cut answer to your question. Part of your decision will have to made from your own instincts, beliefs, and assessment of your kitty during day to day life at home.

The general recommendation for a mammary cancer cat is to do a unilateral mastectomy for even just one lump. Otherwise it is very likely to develop into another tumor on the same side which is what happened to your cat.

Theoretically, then, complete excision of the rest of that chain should be done. However, that sounds good on paper, but there's more to the picture. Her age, the status of her kidneys, her health in general, and the proficiency of your surgeon and type of anesthetic used. She's in the older group, but many 16-year-old cats are very healthy and do very well during surgery.

I don't know enough about her kidney issues to say specifically if the surgery will have an effect on them. You said her kidneys are declining, but you said her creatinine was normal. How were the kidneys assessed? I'm assuming the specific gravity of her urine is why you were told her kidneys are declining or perhaps ultrasound. The cats that we treat that are 16 and have normal creatinines and are on IV fluids before, during, and after the surgery do fine.

I believe you are correct in that her litter box behavior has nothing to do with the cancer.

Regarding the mammary cancer cat surgery itself: certainly removal of a complete chain is a longer surgery and involves disruption of a larger part of the body than the lumpectomy. If your vet uses only gas for anesthesia and is a very proficient surgeon, checks bloodwork prior to the procedure, checks chest x-rays to make sure there hasn't been metastasis already, gives IV fluids and administers pain relief, things could go fine. If, however, you choose the lumpectomy, you can almost be positive that there will be malignancy developing again in the future.

You see why I can't give you a definite answer. There are too many "ifs" for me to be the one to decide. I think, if she were my cat, and she was otherwise healthy and the creatinine was still within normal limits and all the parameters I referred to above were followed, I would choose the unilateral mastectomy. A 16-year-old cat can live many more years these days.

I hope I have given you some additional information to help you with your decision or to clarify some questions you may want to ask your doctor. I wish the best for her and everyone that loves her.

Dr. Neely

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