Breast cancer in dogs: FAQ
Find out how to check your dog for signs of breast cancer, and what to do if you find lumps.
What is breast cancer in dogs?
Breast (or mammary) tumours in dogs appear as lumps of varying shapes and sizes in the mammary glands. These glands can be found around your dog’s nipples. Some lumps are benign and harmless, whereas others may be malignant (cancerous). These can spread to other parts of the body and make your dog unwell.
Mammary gland tumours are typically found in older dogs (around 7 and older), and dogs who are not spayed or are spayed later in life. Breast cancer is much more common in female dogs than male dogs.
What are the signs of breast cancer in dogs?
Your dog’s symptoms will vary depending on what stage their mammary cancer is at.
Symptoms can include:
- lumps in their mammary glands (breasts)
- discharge from the nipple
- inflammation and sore looking skin over the lump
Signs of advanced breast cancer in dogs can include:
- coughing (if cancer has spread to the lungs)
- weight loss
- weakness
- depression
- reduced appetite
These symptoms don't always indicate breast cancer, but if you notice any of them, you should contact your vet.
Important
Some unneutered dogs can have swelling of the breast tissue after their season (a female dog’s period) which is called a false pregnancy – speak with your vet for advice on this.
How do I check my dog for lumps?
- Find your dog’s mammary glands
To do this, look at your dog’s chest and belly. You should see five pairs of nipples running in a line along their underside, from their chest area towards their back legs. Their nipples show where their mammary glands are. Some dogs only have four pairs of nipples, but this is normal.
The easiest time to look is when your dog is enjoying a belly rub and is relaxed. Don’t force them to show you their tummy, as this is very stressful for dogs.
2. Feel for lumps
With your dog in a position that is comfortable for them, gently feel the area around each of your dog’s mammary glands. You should be able to move the nipple and skin gently from side to side and there should be no solid lumps on or around the nipples.
Your dog might let you examine them while they are lying down, or they might prefer you to do this when they are standing.
3. Give your dog lots of praise
Praise them calmly and gently while you are doing this and give them a good fuss or a treat when you are done.
If you do find a lump – whether it is hard or soft – on your pet’s mammary gland, book them an appointment with your vet to get it checked out.
How is breast cancer in dogs diagnosed?
Your vet will check any lumps for:
- size
- swelling
- whether it’s solid or can be moved around
- any ulcers (cuts or scabs on the skin)
Your vet will discuss next steps with you. This may involve checking for any signs of spread of cancer by taking x-rays of your dog's chest, taking samples, and/or advising surgical removal of the mass or the entire mammary gland. Sadly, not all masses will be removed, particularly if they are cancerous and have already spread to other parts of the body.
There are two different types of mass that your vet may diagnose:
Benign tumour
Benign tumours are a non-cancerous tumour. They are less likely to grow back after surgery and they do not spread to other parts of the body.
Malignant tumour
A malignant tumour is an aggressive form of cancer. These tumours quickly spread to other parts of the body and sometimes grow rapidly. They are difficult to treat because they may have already spread by the time you or your vet has found them. If surgery is carried out, they may grow back afterwards.
How is breast cancer in dogs treated?
Surgery is the main method of treatment for breast cancer in dogs. But there may be other options available depending on the tumour and it's location.
Surgery for breast cancer in dogs
Your vet will discuss with you if surgery is the best option for your dog. The earlier the tumour is removed, the better.
The operation may involve removing the lump, the entire mammary gland, or multiple mammary glands. If your dog has many masses throughout their mammary glands, your vet may need to remove the whole chain of mammary glands on one side of their body.
Unfortunately, if the cancer has already spread, or if your dog has a very large tumour that would be very difficult to remove, it is unlikely that surgery will be recommended.
Your vet will discuss the options with you, keeping in mind how advanced the cancer is, and what is best for your dog.
Note
We know dealing with cancer can be an extremely upsetting time. Our Pet Loss Support service is here to help you through if you need to speak to someone.
What happens after surgery?
After your dog has come out of surgery, they will stay in hospital until they are fully recovered from their anaesthetic. Most dogs usually come home the same day, though they sometimes they need to stay in hospital overnight.
It is normal for your dog to have some bruising post-surgery.
How to take care of your dog after surgery
Your vet will talk you through how to look after your dog at home. They will usually ask you to:
- keep an eye on the wound for swelling and discharge
- give your dog pain relief – you’ll have specific instructions on how much medication and when to give them. Do not give your pet any human pain relief unless specifically advised to do so by your vet – some human medications are toxic to pets.
- allow your dog to rest and recover – this often means no exercise until their stitches have been removed
Can neutering help prevent breast cancer?
It's thought that there is a hormonal link to the development of breast cancer. We recommend neutering bitches to help prevent this, and other potentially fatal diseases.
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Reviewed
• 20 May 2025
Next review
• 19 May 2028
