What Are The Signs Of Skin Cancer In Dogs?

Updated April 13, 2021

In places like Australia, we all know how dangerous the sun can be. It can be just as bad for our dogs. Here I will help you decide three things:

• Is my dog is at risk of skin cancer?
• What do I look out for?
• What do I do if it happens?

By ‘skin cancer’ I mean only those tumours caused by sun exposure. Visit this page if you want to see a larger list of lumps on dogs’ skin.

Dogs Breeds Prone To Skin Cancer

Any dog with areas of pink skin lacking pigment is at risk. Common examples are:

• American Staffy
• Border Collie
• Boxer
• Bull Terrier
• Dalmatian
• Jack Russell Terrier
• Staffordshire Bull Terrier

The second crucial factor is the amount of ultraviolet exposure. That means skin cancer is rare in dogs in the UK and northern Europe, and common in dogs allowed to sunbathe throughout the Americas, Africa, Australia and New Zealand.

The picture above shows a simple guide to see if your dog is at high risk. Lightly pinch an area of pink skin, and compare the width of the fold to an area of black skin. If the pink skin is thicker, it’s telling you your dog’s skin is being damaged. You need to act.

Types Of Skin Cancer & Pictures

There are only two common types of skin cancer caused by the sun. They mainly occur in areas with little or no hair coverage, mostly on the belly and inner thighs.

Squamous Cell Carcinoma

Squamous cell carcinoma, or SCC, is the most common and serious. Because it rarely forms a lump it fools dog owners into thinking it’s just a wound or injury.

An early stage SCC looks like any small skin cut, except that it doesn’t heal. There is usually a dark scab over the top like the first picture. Note that it sits in the pink, unpigmented area, not the black spots.

As they grow they often become raw and open, with an ulcerated surface. The second image shows the classic appearance of a circular wound with a distinct edge, quite unlike the ragged edge of a cut or scrape.

This photo shows an SCC that has been left too long. Letting it get this big risks it spreading into the local lymph nodes, from where it’s difficult to stop.

Although there’s no guarantee, it should still be OK as long as it’s taken out soon.

Cutaneous Haemangioma

When small, a haemangioma looks like a small red bump or berry. Here’s one pictured on a dog’s leg, again starting in the pink skin.

Unlike SCC, a haemangioma (hemangioma in the USA) rarely spreads to the lymph nodes. However, they are often rapid-growing and can still cause death if left too long.

They also have another unpleasant feature. As haemangiomas enlarge, their surface breaks open and bleeds with even the slightest knock. Such an example is shown in the second image.

Once again, this can still be safely removed. Note also how unhealthy the rest of the pink skin looks due to years of solar radiation.

Other Skin Cancers

Unlike in people, a melanoma on a dog’s skin is rarely caused by sun exposure. They are also far less likely to spread or metastasise. Most should still be removed, especially on sensitive places like the head or legs.

You can read here about melanomas in the mouth of dogs, which have very different behaviour. Other skin lump pictures can be found here.

Prevention Of Skin Cancer

Once skin cancer appears, there is no good alternative to speedy removal, so I won’t discuss this further. Much more important is preventing skin cancer.

Step 1: Get your dog out of the sun. Whenever the UV index is at 3 or greater, skin damage is likely. This is when susceptible dogs should be kept in the shade or inside.

You can’t trust dogs to do the right thing, especially on those cool, sunny days in late spring and early summer. It’s not only smart, it’s cost-effective to build a shady fenced area if your dog is a sunbather. What ends up causing the death of many dogs is the unsustainable financial burden of repeated operations.

Step 2: Use sunscreen. Here’s Loki’s nose. The pink area gets a dab of sunscreen . He also has a lot of pink skin underneath, but it’s not very practical to put creams there due to the way it picks up dirt. However, if you’re prepared to bath your dog each time, it’s fine there too.

Step 3: Sun shirts. Personally, I think these are very hard to do well, as the highest risk area is the hardest to cover. If you can fit one that covers the groin but still allows for urination and doesn’t just ride up each time they lie down, then go for it.

A normal hair coat protects the skin almost as well as a shirt. This is a reminder to be especially careful if you’ve shaved your dog for summer.

The main message is (of course) to get those small lesions checked before they become large ones. Have a safe summer!

Related: Common Pet Emergencies Of The Summer Holidays

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.