Vet checking dog with stethoscope with owner present

Breast cancer in dogs

Breast (mammary) tumours in dogs appear as cancerous lumps of varying shapes and sizes in the mammary glands - these glands can be found around your dog’s nipples.

Breast cancer or ‘mammary cancer’, as it’s known in dogs, is much more common in female dogs.

Symptoms of breast cancer in dogs

Your dog’s symptoms will vary depending on what stage their mammary cancer is at.

Symptoms can include:

  • lumps by their nipples (mammary glands)
  • discharge from the nipple
  • inflammation and sore looking skin over the lump

Where the cancer is more advanced you may see:

  • coughing (spread to the lungs)
  • weight loss
  • weakness
  • appearing unwell
Important: Some unneutered dogs can have swelling of the breast tissue as a normal event after their season (female dog’s period) which is called a ‘false pregnancy’ – speak with your vet for advice on this.

How to check your dog for breast cancer

Find your dog’s mammary glands

To do this, you need to 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. Please don’t force them to show you their tummy, this is very stressful for dogs.

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. 

Give them lots of praise

Praise them calmly and gently while you are doing this and give them a good fuss or a treat to thank them when you are done. It should only take a minute or so. 

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 will my vet identify breast cancer in my dog?

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)

If cancer is suspected, your vet will discuss next steps with you. They may want to sample the lump/s, others may book your dog in for removal of the lump/s and sometimes surgery may not be possible.

What is a malignant tumour?

A malignant tumour is an aggressive form of cancer. These tumours quickly spread to other parts of the body and grow rapidly.
They are hard to treat because they may have already spread by the time your vet has identified them and, if surgery is carried out, they may grow back afterwards.

What is a benign tumour?

Easier to treat, these tumours are less likely to grow back after surgery and do not spread to other parts of the body.

Treatment of breast cancer in dogs

Alison Thomas - Head of Veterinary Services in Blue Cross uniform
This advice has been approved by our Head of Veterinary Services at Blue Cross


Surgery is the best option for your dog. The earlier the tumour is removed, the better.

The operation will involve removing the cancerous cells from your dog’s body. In some advanced cases, your vet will need to remove the whole chain of mammary glands on one side of their body.

Unfortunately, if your dog has multiple tumours or a very large tumour, then surgery may not be recommended. This is because the cancer may be too advanced and may have spread or be likely to regrow after surgery.

Your vet will discuss the options with you, keeping in mind how advanced the cancer is, and what is best for your dog. We know this can be an extremely upsetting time and are 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. They can usually come home the same day, though they do sometimes need to stay in hospital overnight. 

It is normal for your dog to have some bruising post-surgery due to the delicate area that has been operated on.

Your vet may ask you to bring your dog to follow-up appointments so they can check them over for new tumours and any regrowth from the removed tumour/s. 

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 many tablets 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.
  • make sure your dog is resting and is not exercising – this can mean placing your dog on crate rest, especially if you have an active pooch

Can neutering help prevent breast cancer?

Evidence suggests neutering (spaying) your dog, especially when they are young, significantly reduces the risk of breast cancer.

On average, one in every four unneutered female dogs is affected by breast cancer. We recommend neutering bitches to help prevent this, and other potentially fatal diseases.

If your dog has been diagnosed with cancer and has not yet been neutered, your vet may recommend this, as it helps to reduce the risk of more tumours developing after surgery.

— Page last updated 30/05/2023