Mammary Masses in Female Dogs and Cats
Finding a lump near your pet’s mammary glands can be alarming. Mammary masses are relatively common in female dogs and cats, especially those that are older and unspayed. While some are benign, many are cancerous, so it’s important to take any mass seriously and seek veterinary evaluation.
What Are Mammary Masses?
Mammary masses are growths that develop in the mammary (breast) tissue. These may present as a single lump or multiple nodules along the mammary chain, which runs from the chest to the groin area. Masses may be firm or soft, and they can grow slowly or rapidly. In some cases, they may ulcerate or ooze if left untreated.
Risk Factors
Spay status: The biggest risk factor is being unspayed or spayed later in life. Spaying before the first or second heat cycle drastically reduces the risk.
Age: Middle-aged to older pets are more likely to develop mammary tumors.
Species: Mammary tumors are more likely to be malignant in cats than dogs.
Hormonal exposure: Repeated exposure to estrogen and progesterone increases the risk.
Signs to Watch For
New lumps or bumps along the mammary chain
Swelling, redness, or warmth in the area
Discharge or ulceration of the skin
Changes in size or shape of a known lump
Discomfort when touched
If you notice any of these signs, schedule a veterinary visit as soon as possible. Early detection improves treatment options and outcomes.
What Happens at the Vet?
Your veterinarian will perform a physical exam and may recommend:
Fine needle aspiration (FNA): A small sample of cells is collected for evaluation.
Biopsy or surgical removal: Masses are often removed and sent for histopathology to determine if they are benign or malignant.
Chest x-rays or abdominal imaging: These help check for spread (metastasis), especially to the lungs or lymph nodes.
Bloodwork: To assess overall health and surgical readiness.
Treatment Options
Surgical removal: This is the most common and often most effective treatment. Depending on the number and location of masses, a partial or full mastectomy may be recommended.
Spaying: If the pet is not already spayed, this is often done at the same time to reduce hormone-driven tumor growth.
Chemotherapy: Recommended in some cases, especially if the mass is aggressive or has spread.
Palliative care: If surgery isn’t an option, pain management and wound care may be provided.
Prognosis
Prognosis depends on the size of the tumor, whether it is benign or malignant, and whether it has spread. Benign tumors that are removed early often carry an excellent prognosis. Malignant tumors caught early and surgically removed can also have good outcomes, though more aggressive cancers may require additional treatment.
Prevention and Monitoring
Spay your pet early (before the first or second heat cycle, if possible)
Regularly check your pet’s mammary area for new lumps
Schedule annual veterinary exams
Conclusion
Mammary masses in female dogs and cats are treatable, especially when caught early. Spaying remains the most effective preventive measure. If you find a lump, don’t wait—early action gives your pet the best chance for a healthy outcome.
If you’ve recently discovered a mammary mass on your pet, contact your veterinarian to schedule an exam and discuss the next steps.
