Mammary Gland Tumours
Common in intact and late-spayed females; roughly half are malignant.
What is Mammary Gland Tumours?
Mammary tumours are strongly linked to lifetime exposure to reproductive hormones. In dogs spayed before their first heat, the lifetime risk is under 1%; after multiple heats, risk rises to around 25%. About half of mammary tumours are benign and half are malignant, and the two often can't be told apart without biopsy.
Common signs and symptoms
Signs vary between dogs and can be subtle at first. Watch for the following, especially if several appear together or persist for more than a few days:
- One or more firm lumps along the mammary chain (belly)
- Ulceration or discharge from a mammary lump
- Rapidly growing or fixed masses (concerning features)
- Swelling, warmth, or discomfort across a whole gland (inflammatory carcinoma — urgent)
Risk factors
Certain dogs are more predisposed. Understanding risk helps you screen earlier and act sooner.
- Intact or late-spayed females
- Age 8+
- Certain breeds: Poodle, Dachshund, Spaniel breeds
- Obesity in early life
When to see a vet
Use this as general triage guidance, not a substitute for veterinary advice.
- Book a routine appointment if: you feel any lump along the mammary chain, even a small one.
- Seek urgent care if: a mammary lump is red, painful, or growing rapidly — inflammatory mammary carcinoma needs immediate assessment.
Diagnosis and management
Surgical removal is the mainstay; the extent (lumpectomy vs. chain mastectomy) depends on number, size, and location. Histopathology guides whether further treatment is needed. Concurrent spay is often recommended. Early spay remains the strongest preventive measure.