Dog with cancer lump on the head
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Dog cancer lumps

By Alice Lang Copywriter

Updated on the

Unfortunately, cancer is the leading cause of death in dogs aged 10 and over. The good news is that half of canine cancer is curable when caught early - so it’s essential to understand dog cancer lumps, what to look for and how to detect the early signs of cancer.

There’s nothing that puts more fear in the hearts of pet owners than the words “Your dog has cancer”. And when you’re stroking your canine buddy, only to detect a strange lump or mass, it’s easy to go straight into panic mode and assume the worst.

Thankfully, most lumps, bumps and masses on dogs are benign - but that doesn’t mean you should just ignore it or hope it goes away. If you’re a dog owner, it’s so helpful to understand the different types of dog cancer lumps and cancer symptoms, so you can get your pup checked out at the earliest opportunity if needed.

What is dog cancer?

The Kennel Club explain that “Cancer means an abnormal growth of cells and, unfortunately, it's a common disease of all dogs. It may be benign (slow-growing, removable) or malignant (aggressive, spreading throughout body) with roughly one in four dogs eventually succumbing to the disease.”

“For dogs over 10 years of age, approximately 50% of deaths are cancer-related; and like us, there are many different types of cancers resulting in a huge variation in clinical signs observed.”

Dog cancer lumps

Dog cancer can be treated. But just like human cancer, the results come with varying success. The best chance your pup can get at surviving cancer if it were to get it, is early detection. Catching cancer early means it wouldn’t have spread to other parts of the body - making it much easier to treat.

One of the most common ways of catching dog cancer in its early stages is by finding a lump, bump or mass which wasn’t on your pooch before or spotting changes in an existing lump.

Types of dog cancer lumps and tumours

There are many types of dog cancer©Pexels

Skin cancer

The most common form of cancer in dogs, skin cancer is often caused by overexposure to the sun and sunburn - especially in dogs with shorter or lighter coats. The AKC notes that the most common types of skin cancer in dogs include:

  • Malignant melanoma
  • Mast cell tumours
  • Squamous cell carcinoma
  • Histiocytic cell tumours
  • Fibrosarcoma

Check your dog’s skin for scabs, lumps, bums or slow healing wounds and sores. Skin cancer could present itself as black, brown, red, pink or grey in colour. Anything abnormal should be checked over by your vet.

Hemangiosarcomas (blood vessel)

This type of cancer can develop as a skin cancer but is normally linked to the spleen. Hemangiosarcomas is cancer of the blood vessels which is more common in dogs than any other species. Common symptoms are pale gums and difficulty breathing, as well as a drop in energy.


This slow-growing dog cancer lump is found in the connective tissue of a dog’s skull, spine, rib and pelvis. If you’ve got a large-breed or old dog, keep an eye out for this one, as it’s common in these types. The lump can often be felt with the hands when it first appears - hence why it’s so important to get lumps checked at the earliest opportunity.


“Unspayed female dogs are at risk for mammary or breast tumours. In dogs, there is a 50-50 chance that a mammary mass is cancerous/benign. This is the reason why veterinarians often insist on the importance of spaying your dog,” explains Pet Health Network.

“Mammary tumours develop because of spikes in female hormone (estrogens) that take place during a dog’s heat cycle.”

Symptoms include a palpable dog cancer lump or bump in the mammary tissue, which might produce a discharge or secretion.


An oral tumour can start from the bone, teeth or soft tissue structures of the upper or lower jawline. Most oral tumours are, unfortunately, malignant. Watch out for blood in your dog’s saliva, smelly breath, a swelling in the face and of course, a lump or mass in the mouth.


Nasal tumours are pretty rare in dogs, but generally, don’t have a good prognosis.

The National Canine Cancer Foundation notes that: “Some of the most common clinical signs may include bloody nasal discharge, nasal discharge containing mucus and pus, facial deformity from bone erosion and subcutaneous extension of the tumour, sneezing, shortness of breath, abnormal protrusion of the eye”.

Osteosarcoma (bone)

Greyhounds, Great Danes and other large breeds are prone to developing bone cancer, which is often found on a dog’s legs. If your dog is limping with no clear reason, it could be a sign of bone cancer.

Sometimes, you’ll be able to physically see a dog cancer lump on the body or a severe inflammation around the site of a tumour. Other symptoms include pain and arthritis-like symptoms. Other types of dog cancer lumps and tumours include:

  • Abdominal
  • Lung
  • Lymphoma
  • Apocrine Gland Carcinoma (anal)
  • Transitional Cell (urinary)

Symptoms of dog cancer

The National Canine Cancer Foundation says there are 10 warning signs your dog might have cancer:

  • Abnormal swellings (dog cancer lumps) that persist or continue to grow
  • Sores that do not heal
  • Weight loss
  • Loss of appetite
  • Bleeding or discharge from any body opening
  • Offensive odour
  • Difficulty eating or swallowing
  • Hesitation to exercise or loss of stamina
  • Persistent lameness or stiffness
  • Difficulty breathing, urinating, or defecation

What to do if you find a lump on your dog

Most of the time, a lump or bump on your dog will be nothing to worry about. It's important to remember that not all lumps are dog cancer lumps. However, as we said, it’s best to get lumps checked out at your next vet’s appointment as a precautionary measure. Some lumps, in particular, should be considered as more of an emergency. If the lump:

  • Is particularly large,
  • Appeared or grew quickly,
  • Is bothering your pet (scratching, licking),
  • Is an open sore,
  • Has changed in feel or texture,
  • Is black or purple,
  • Is leaking discharge or pus.

Then please get the lump checked out immediately by your vet. So, now that you're familiar with dog cancer lumps and what to look out for, you can keep your dog safe and get him checked out at the earliest opportunity - well done!

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