All you need to know about skin cancer in dogs

We all hate the thought of our pets being unwell, and any sort of cancer is a particularly scary prospect. Luckily, many cancers, including skin cancer, are very treatable if detected early – and by understanding the signs to look for and what to expect from treatment, you’ll be in the best position to cope with any diagnosis and help your dog recover.

Yes – skin cancer happens when the cells inside a dog’s skin start to divide and grow abnormally. Over time, this can lead to a mass or tumour that can then spread (metastasise) to other parts of the body.

‘While skin cancer in people is often caused by overexposure to the sun, this is much rarer in dogs,’ says Petplan veterinary expert Brian Faulkner. ‘Instead, dogs that develop skin cancer are predisposed to developing these tumours as a result of their genes.’

There are many different kinds of skin tumour. Some form within the skin, while others develop just beneath it. Either type can be benign (not usually harmful) or malignant (faster growing and usually harmful). Although many lumps and bumps that dogs develop are harmless, it’s always important to get them checked out by your vet as soon as possible.

Skin cancer is relatively common, with the British Small Animal Veterinary Association (BSAVA) suggesting it can affect 25% of dogs.

‘One of the most common – and the most serious – skin cancers in dogs is known as a mast cell tumour. This occurs when mast cells (normal cells that release histamine in the skin) become malignant,’ says Brian. While these tumours can affect any breed, Boxers and Golden Retrievers seem to be particularly susceptible. ‘These tumours come in many forms, ranging from a raised lump on the skin to a wart-like growth or even an angry, red, raised area on the skin’s surface. I have seen lumps which owners assumed were simply tick bites turn out to be mast cell tumours. Unfortunately, we still don’t know what causes these normal cells to suddenly become cancerous, although genetic factors often play a role.’

While any dog can develop skin cancer, your dog’s breed and age do play a part. Genetics is a leading cause of canine cancer, with certain breeds more likely to develop it. ' Senior dogs are also at a higher risk, as old age brings an increased probability of tumours and cancer,’ explains Brian.

'It may be possible to help minimise the risk of environmentally caused tumours, such as squamous cell carcinoma, a form of skin cancer linked to sun exposure,’ says Brian. Skin cancers due to sunburn are much more common in cats than dogs, as cats generally like to sunbathe more. Even so, Brian recommends taking extra precautions on particularly sunny days, to prevent your dog being exposed to the sun when it’s at its strongest. ‘Consider keeping your dog inside during the hottest and sunniest period of the day, go for walks early or late, and use a dog-friendly sunscreen to protect their skin.’

The most useful thing you can do to protect your dog from skin cancer is to regularly check for changes to their skin. Early detection and treatment can make all the difference.

Cancerous skin lesions on dogs vary enormously. Skin cancer on a dog’s nose might look very different from cancerous skin lesions on a dog’s flank. ‘The best way to spot any possible signs of skin cancer is to groom your dog regularly,’ says Brian. ‘In addition to helping you consistently check your dog’s skin for any lumps or changes, this is a great way to bond with your dog and keep their skin and coat in great condition.’

Signs of skin cancer in dogs include:

• Bumps or lumps on the skin
• Red or crusty areas
• Changes in skin colour
• Scabs on the ears or nose
• Unexplained wounds that don’t heal

‘While grooming your dog, pay attention to areas that aren’t normally stroked, touched or looked at, including their armpits, inside the groin, between their shoulder blades, down the back of their neck, under the tail and the anus,’ says Brian.

Any bumps or skin tags you find might not be anything to worry about – but it’s essential to get them checked over by your dog’s vet. As Brian explains, ‘There are misconceptions out there, including the idea that if a lump is freely moveable, or isn’t painful to the touch, it must be benign – which isn’t always the case. It’s vital to get your vet’s professional opinion whenever you spot something out of the ordinary.’

If your vet suspects a lump could be cancerous, your vet will want to perform some simple tests to explore this. ‘Cells can easily be extracted using a procedure called a fine-needle aspirate,’ explains Brian, ‘although delicate areas, like the tips of the ears, may require a biopsy under sedation. Once acquired, the cells are placed on a slide and examined under a microscope. Depending on the findings, the vet may then recommend a tissue biopsy, where part of the tissue is removed for examination, to confirm the diagnosis. This is usually done under deep sedation or general anaesthetic.’

If there are signs of skin cancer, surgery is usually recommended – with or without chemotherapy, depending on the stage of cancer. ‘Keep in mind that if it’s caught early, most dogs with skin cancer have a good chance of recovery, and the condition can be managed well enough to ensure it doesn’t affect your dog’s quality of life.’