Mammary Tumors in Dogs and Cats: Part II

Read about mammary tumors in dogs in Part I.  

Feline Mammary Tumors 

About 80-90% of mammary tumors in cats are malignant adenocarcinomas, a type of cancerous tumor. The good news is that cats that are spayed before six months of age have a 91% reduced risk of developing this cancer. However, cats spayed after two years of age have no risk reduction. This is why early spaying is highly recommended in cats.  

Next Steps 

After your family veterinarian or a board-certified veterinary oncologist diagnoses your cat with malignant adenocarcinomas, they will discuss treatment options, including: 

• Surgery
  • A staged bilateral chain mastectomy is a surgery where all mammary glands on one side are removed and then 2-4 weeks later, the surgery is repeated on the opposite side. 
    • This surgery is recommended in cats because it significantly reduces the chance of tumor recurrence compared to traditional surgeries that only remove the mass itself. 
    • With a staged procedure, there are fewer complications with wound healing compared to removing both mammary chains in a single procedure. Survival time is also improved in cats with bilateral surgery compared to those treated with unilateral mastectomy (where both sides are removed at the same time).  
• Chemotherapy
  • After recovering from surgery, chemotherapy is recommended to reduce the risk of metastasis (the spread of the cancer). 
  • Similar to dogs, several studies support the use of chemotherapy while others reveal no significant survival benefit. At Animal Emergency & Referral Center of Minnesota, our Oncology Service recommends chemotherapy since mammary carcinomas have a high risk of spreading. 
  • The vast majority of cats tolerate chemotherapy with zero to minimal side effects. 
• NSAIDs
  • Low doses of NSAIDs may be prescribed if surgery and/or chemotherapy are not pursued. 

Prognosis  

Tumor size, histologic grade, and if the cancer has spread all play a role in your cat’s prognosis. Your family veterinarian or board-certified veterinary oncologist will consider the following factors: 

• Cats with tumors <2cm that are removed with aggressive surgery have a median survival time of over 3 years – meaning half of these cats live longer than three years while half do not. 
• Cats with tumors 2-3 cm have median survival times of about 2 years.
• Cats with tumors >3cm have median survival times of only six months.
• If the cancer has spread, this reduces the anticipated survival time further.  

Finding a lump anywhere on your pet is an alarming discovery, which is why it’s important to consult with your family veterinarian. If you suspect your dog or cat has a mammary lump, or if you have any other concerns about your pet’s health, consult with your family veterinarian. Once a diagnosis is determined, they may choose to refer your pet to a board-certified veterinary oncologist for guidance on your pet’s specific type of cancer, as well as treatment and management options.  

Learn more about Animal Emergency & Referral Center of Minnesota’s Oncology Service here.  

More Reading: 

• Chemotherapy and Quality of Life in Dogs and Cats  
• Debunking Pet Cancer Myths   
• Early Detection of Cancer in Dogs and Cats: 5 Things Pet Owners Can Do  
• 5 Most Common Pet Surgeries at AERC