Skin cancer in dogs: causes & prevention

Back in 2019, the genetic risk factors in one of the most common cancers in dogs – mast cell tumours – were identified by researchers at the Animal Health Trust, in association with the Broad Institute in the UK, Utrecht University and Uppsala University.

The research team studied over 800 DNA samples from Labradors and Golden Retrievers. It’s been long known that these two popular breeds are the most susceptible to developing the disease.

Their findings showed that 70% of Labradors and Golden Retrievers carry the genetic marker for mast cell tumours.

Now that we know what genes cause it, there is hope that scientists will be able to create preventative and diagnostic tests.

What are mast cell tumours?

Mast cell tumours (MCTs) are one of the most common skin cancers in dogs. They occur in mast cells, which are normally involved in immune response. They mutate and start proliferating uncontrollably.

Mast cell tumours appear on the skin and very rarely in internal organs. They're usually noticed during physical examination at the vet.

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They vary in size and appearance. They can look like a lesion, hairless, or simply feel like a lump or a soft movable mass just underneath the skin. Most frequently they are around 3cm large but can grow up to around 20cm to 30cm.

Mast cells are involved in immune response and contain a substance called histamine, which is released when the immune system detects an allergen that it needs to attack. This can lead to uncontrollable allergic reactions when the cells begin malfunctioning due to cancer.

The prognosis and treatment depend on the grade of MCT. Some of the lower grades are removed surgically. A higher grade, meaning a more malignant type of MCT, may require a combination of surgical intervention, chemotherapy and other forms of treatment.

How likely is a dog to get mast cell skin cancer?

The Animal Health Trust’s team compared DNA from healthy dogs to DNA from dogs with mast cell tumours. The results showed that a dog that has two copies of the risk factor DNA is three to four times more likely to develop the disease.

Which dog breeds get mast cell tumours?

In just one year, between July 2021 and June 2022, we saw 951 dog insurance claims for mast cell tumours. These are the dog breeds most commonly affected according to our data:

1. Labrador Retriever (13% of all mast cell tumour claims)

2. Staffordshire Bull Terrier (12%)

3. French Bulldog (7%)

4. Golden Retriever (7%)

5. Boxer (5%)

Some breeds are more susceptible to it than others.

Other breeds thought to be prone to developing the disease are Schnauzers, Boston Terriers, Pugs, Terriers, English Bulldogs, Cocker Spaniels, Beagles, Rhodesian Ridgebacks, Weimaraners and Shar Peis.

How common is cancer in dogs?

One in four dogs will develop cancer throughout its lifetime, according to the Animal Health Trust.

Between July 2021 and June 2022 the most common cancers in dogs that we saw pet insurance claims for were mast cell tumours followed by lymphoma.

Other common types of cancers found in dogs are: skin cancer, osteosarcoma, breast cancer and cancer of the blood vessels.

All breeds can be affected by cancer, but some breeds are more susceptible to particular types of cancer.

If you are considering buying a certain breed or wonder about the types of cancer your dog is susceptible to, consult with a veterinary professional to learn more.

Symptoms of cancer in dogs?

Cancer symptoms depend on the type of cancer, but common signs of cancer are:

• Swelling or a lump

• Wounds or sores that don’t heal

• Bleeding from a body orifice

Other signs can be difficulty breathing, going to the toilet or swallowing; lameness, loss of appetite.

You can feel your pet's body for lumps if you're worried, but bear in mind that not all lumps mean tumour or cancer.

Always take your dog to a vet if you suspect something’s wrong.

What causes cancer in animals and can it be prevented?

The causes of cancer can be genetic, environmental or viral.

Not much is known about the exact causes of cancer, but it is known that environmental carcinogens like pesticides, UV light, asbestos, radioactive materials, environmental cigarette smoke can increase the risks.

It is hypothesised that some low quality pet foods can also contribute to the development of cancer. Certain artificial preservatives and ingredients usually used in kibbles are believed to cause cancer.

In addition, we know that genetic predisposition plays a role, too, as it does with MCTs.

Hormones can also have an impact. Although the evidence is inconclusive, many veterinary professionals believe that chipping a female dog before her first heat reduces her risks of developing mammary cancer.

The older a dog is, the more likely they are to develop cancer. As dogs live longer today, more of them get cancer, which is why more cases are recorded.