Vancouver Feline Hospital - Cat Veterinary Clinic

Feline Mammary Cancer (Cat Breast Cancer)

Cancer is scary - if your cat has been diagnosed with cancer, please refer to our support pages - there is LOTS that you and your veterinarian can do to ensure compassionate quality of life for your cat.

This article is written to provide information. You will find a lot of medical information here, not all of it "dumbed-down" - it may be overwhelming and scary at first, but we have found that once over all the hairy humps, the information really does help! Remember, there is no such thing as a dumb question, so keep asking until you feel you understand as much as you want to about what is going on with your cat.

The first time your veterinarian examines your cat because of the lump(s), he/she will probably tell you that the lump(s) can be caused by a number of things:

1. Malignant mammary cancer
2. Benign mammary tumours
3. Mammary hyperplasia (FMH)
4. Mastitis
5. Foreign body or abcess-like infection
   

The last two are fairly simple to rule-out. To differentiate between the first three, the veterinarian may suggest doing a Fine Needle Aspirate of the lump and sending the slides to the lab for cytology. In FMH, cytology is of a non-inflammatory or non-diagnostic type. If any fluid can be expressed, that may also be sent for analysis.

If the veterinarian is concerned because sometimes FMH can be a precursor to mammary cancer, a biopsy may be suggested - this involves surgery and the risks and benefits of that will be discussed then. Biopsy results will definitely confirm the diagnosis.

For all breast lumps, veterinarians prefer to collect a "minimum data base" - basic information that can significantly help in diagnosis, staging and decision-making. This data-base includes a complete blood count, biochemistry screen, FeLV and FIV test, thyroid hormone test and chest x-rays (3 views). You need to discuss costs with your veterinarian so that decisions can be made that allow a diagnosis to be made and you to provide optimum care for your cat.

Mammary gland neoplasia is the third most common form of cancer in cats. It is more common than in humans but less common than in dogs. Older female cats (average age 11 years) are at most risk, and there are reports that Siamese are also at increased risk.

Cats that are spayed have a significantly reduced risk (less than half) of developing mammary cancer compared to sexually intact or late-spayed cats. Cats that have been treated with progestins (birth control or for skin disease, male or female) have increased risk.

These are aggressive cancers. There is often more than one lump, it may have already spread to the lymph nodes and lungs, and they often ulcerate (burst open into bleeding sores).

Prognostic factors: (trends - individuals can buck the trends)

• Breed - Domestic shorthairs (DSH) survive longer
• Age - Younger cats survive longer
• Tumour size - The larger the tumour the poorer the prognosis
• Metastasis - Never good news - poor prognosis
• Well-differentiated tumours - longer survival
• Low AgNOR counts - longer survival
• Histologically complete surgical resection - longer survival
  

Once cancer is suspected, your veterinarian will want to stage the cancer - this process gives critical information and helps with those hard decisions. (e.g. is surgery or chemotherapy an option or should we opt for pain relief only?) Staging is based on the physical examination, minimum data base, examination and/or biopsy of inguinal lymph nodes. Chest x-rays are important because spread to the lungs are most common. Abdominal ultrasound may show spread to other organs.