Mammary Tumors in Cats


Mammary Tumors

Question: I found out on july 8 that my cat boo, has mammary cancer. He's had a radical unilateral mascetomy and the biopsy shows that its in his lymph glands but not in his lungs which was the reason i chose to put him through the surgery in the first place because they were clear. so far, I have chosen not to do chemo or radiation etc . I am waiting for my vet to find out which lymph nodes it was found in and the size of it. because i want to possibly track the most likely course it will take so i can prepare for his end days to make him as comfortable as possible. I am being a realist about this and know how dismal the outlook for boo is ,and to put him through treatment seems selfish .although if my vet said to me that a certain treatment would give him quality and quanity, quanity in my head being 2-3 years i'd take the chance because i love him so and i know he loves living life. they gave him a few months. last summer he weighed 19 pounds and now he ways 10 pounds although he does'nt look emmeciated because he is a big cat and his appetite for the most part is pretty hardy. By the way he's a long haired black brown bear of a cat and just happens to have a little siamese in him, read its prevelent in them although its extremly rare in male cats of any distiction. I quess I'm writing to you for any insight on this matter ,and conformation on my decision that ya miracles happen, but is it worth the risk, expense, and disappointment if all fails. looking forward to hearing from you doc. karen

Answer: Karen-

Mammary tumors occur less commonly in male cats than in female cats, as you are aware. Prior use of megestrol acetate (Ovaban Rx) in a male cat can predispose to mammary tumors. I do not know if this would change the prognosis if it were found to be the problem, but I think a veterinary oncologist might know.

The prognosis for mammary tumors in cats varies the most based on the size of the tumor when it is removed. For tumors less than 2cm in diameter the prognosis is best. Cats with tumors of this size at the time of the surgery have a median survival time post-surgery of about 3 years. For tumors greater than 3cm in diameter, the median survival time is less than one year. This is from MacEwen EG et al, "Prognostic factors for feline mammary tumors" Journal of the American Veterinary Medical Association, 1984.

Sometimes the pathologist gives an indication that the tumor type appears to be especially aggressive and this should be factored into decision making, as well. As you have done, X-rays of the chest and examination of any fluid found in the chest to look for metastases prior to doing surgery is best. Removal of regional lymph nodes at the time of surgery is generally recommended, as well.

The most common recommendation for dealing with mammary tumors in cats at this time, in the references I have, is to do a radical mastectomy of both mammary gland chains and to spay females who have not been spayed already. (I know that doesn't apply to Boo).

If the tumor was less than 2cm in diameter I think that surgery alone may be all that is necessary. For tumors over 3cm in diameter chemotherapy will benefit approximately 50% of cats and in that circumstance it seems worthwhile to consider it. The decision is hardest when the tumors are 2 to 3 cm in diameter. In this case, the lymph node examination and pathologist's opinion may help in decision making.

It is best to consult with an oncologist about chemotherapy since chemotherapeutic profiles change somewhat frequently. At the present time, I think that combinations using two or more medications among adriamycin, cyclophosphamide, mitoxantrone and/or carboplatin are the most common recommendations.

If this doesn't cover the questions entirely, please feel free to write for clarification.

Mike Richards, DVM 8/4/2000

Mammary Tumor in cat

Question: My 8 yr. old cat has a mammary tumor and is having surgery next week. I want as much info on this subject as possible. I have other pets, too, and keeping up with VET news will keep me "on the cutting edge!" Elizabeth-

Answer: Mammary tumors in cats are malignant approximately 90% of the time. This makes it very important to try to remove them as early as possible, so it is good that you are going ahead with surgery.

It is a good idea to have X-rays taken of the chest of cats prior to surgery for mammary tumors, since some cats already have metastatic tumors in their chest at the time that the tumors are found. In cats, the tumors in the chest may look like interstitial pneumonia due to many small tumors, rather than a large mass that is easily seen.

Tumors that are less than 2cm in diameter have a much better prognosis than tumors that are over 3cm in diameter. In between, the prognosis must be really variable because it doesn't seem to get reported. For tumors less than 2cm, the mean life span after surgery is supposed to be about three years. For tumors over 3cm in diameter the mean survival time is supposed to be about 6 months.

Most surgical texts recommend doing a unilateral mastectomy in cats with mammary tumors affecting a gland on one side. Cats usually have 4 pairs of mammary glands and a unilateral mastectomy is removal of all 4 glands on one side. If there are tumors in the other mammary gland line (sometimes these are hard to find prior to surgically prepping the patient) it may be possible to remove the mammary glands on both sides at the same time but usually it is necessary to remove the most severely affected side and wait three to four weeks for that side to heal before removing the mammary glands on the other side. "Lumpectomy" is not a recommended procedure for cats for most cases of mammary gland cancer. I do think that a case can be made for removing the lump if there is some reason to question what it is during the surgery (if it just doesn't look like cancer) and then submitting it for histopath and going back and removing the whole mammary line if it does turn out to be an adenocarcinoma but not many veterinary surgeons agree with that approach, based on the literature.

It is a really good idea to have a pathologist examine the tumors after removal. Each individual tumor found should be examined, if possible. In cats, lobular hyperplasia and fibroepithelial hyperplasia can be mistaken for mammary tumors, according to Dr. Fossum's book, "Small Animal Surgery". The pathologist can also give some idea of the likelihood of malignancy and the prognosis based on examination of the tissues.

At the present time there is not a lot of enthusiasm for chemotherapy as a primary treatment and not much more for it as an follow up to surgery, either. However, this information changes rapidly and if the lumps do turn out to be mammary adenocarcinoma (most common type of mammary tumor in cats) it would be a good idea to ask your vet to check with the oncologist he or she refers cases to for the latest information on chemotherapy for this condition.

The last "mammary tumor" we removed from a cat turned out to be a granuloma ( a benign mass), so there are some times when a good outcome occurs. I hope that you have this kind of luck.

Mike Richards, DVM 4/29/2000

Mammary tumor

Question: Hello,

I just recently subscribed to this service because I have a question about my 12 year old Siamese cat.

I took her in to the vet about three weeks ago because I found a growth that appeared near her mammory glad. The vet said that it was probably a mammory glad tumor and that it was probably bad news. She did testing that day - blood work and a some sort of sample of the gland or of the growth. When she called me she told me that it could be good news because it was more liquidy than tumors and more like a cyst. When the tests came back, she seemed to think that it was benign. She recommended that I still remove it though, just in case. We made an appointment two weeks later for surgery. When I took her in for surgery, they called me after they did the x-ray. They said that it actually did look like cancer and it looked like it had spread to her lungs. They said that there was really nothing that they could do. They said that surgery would not help the cancer go away, but it might alleviate pain related to possible ulceration that could occur later to the tumor. Because the tumor is not ulcerated now and they said that there were also great risks of going into surgery when cancer had progressed that far, I decided not to have it removed.

What I want to know, if you can help, is did I make the right decision? And, most importantly, is there really not anything that can be done now? Also, did waiting two weeks to go into surgery cause it to spread to the lungs? Please help me if you can - I love my cat so much and I don't know how to deal with this. What can I expect and how can I make it easier for my kitty. She does not seem to know what is going on now, but I assume that she will soon?

Thank you very much, C. M.

Answer: C-

I think it would be a good idea to ask that the X-rays be evaluated by a veterinary radiology specialist. While there are many veterinarians who are quite skilled at reading X-rays, general practitioners just don't see as many X-rays as specialists. Getting a second opinion on an X-ray of this importance is warranted.

Surgical excision of mammary tumors is recommended if they have not spread. Radical surgical excision is usually best in cats due to the high rate of malignancy of mammary tumors in cats. Chemotherapy is helpful in some cats, usually using adriamycin, but it does not appear to help in all cases. If the tumors have spread to the lungs, the prognosis is very bad. If you wish to try to treat, anyway, then chemotherapy is probably the way to go. There are veterinary oncology specialists and it is worthwhile to have one consult with your vet, or possibly see your cat, to give you the best evaluation of the possibilities for therapy.

This is a very tough situation to be in. It is not likely that the delay of two weeks made a significant difference. There are no statistics that I know of to evaluate the risks of waiting between initial clinical signs and treatment, in cats, but for similarly aggressive tumors in humans a wait of this time period doesn't seem to affect the outcome much.

I am sorry that I can't be much more help. I really do think it would be best to have the X-rays looked at. They can be sent by overnight delivery to a radiologist and you can have a second opinion pretty quickly.

As time goes on, concerns such as appetite maintenance, pain relief, complications of chemotherapy or other things related to this problem may come up. Please feel free to write and ask questions about any of these matters.

Mike Richards, DVM 12/16/99

Last edited 01/30/05


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...