Skin cancer happens when cells in the skin begin to grow in an uncontrolled way, forming a lump, sore or change on the skin. Some skin cancers grow slowly and stay local, while others can spread more quickly if left untreated.
Checking your dog’s skin regularly is one of the simplest and most effective ways to spot problems early. Many lumps and bumps are harmless, but if a growth does turn out to be cancerous, finding it early can make a big difference to your dog’s outcome.
There are several types of skin cancer seen in dogs. Each behaves a little differently, which is why veterinary assessment is so important.
These are the most common skin tumours in dogs. They develop from mast cells, which play a role in the immune system. Mast cell tumours can appear almost anywhere on the body and may change in size over time, sometimes growing very quickly.
Some breeds are more prone, including bulldogs, Boston terriers, pugs, Staffordshire bull terriers and retrievers. Mast cell tumours range from slow-growing and mild to more aggressive forms.
Melanomas develop from pigment-producing cells. On the skin, they often appear dark brown or black and, in dogs, many skin melanomas are benign (non-cancerous).
However, melanomas found in the mouth, under the nailbed or around the lips and anus are more likely to be malignant and can spread. Unlike in people, sunlight is not thought to be the main trigger in dogs, and genetics may play a role.
This type of skin cancer is sometimes linked to sun exposure, particularly in dogs with light skin, thin coats or areas with little fur. Squamous cell carcinoma can be tricky to spot early, as it may look like a small patch of red, sore or scabby skin at first.
Over time, it may form a firm or ulcerated lump and can spread into surrounding tissue, making early treatment especially important.
These tumours arise from connective tissues and can vary in how aggressive they are. They are often round, fleshy lumps that may feel soft or firm and are commonly found on the legs, chest or head. They tend to occur more often in older dogs, particularly medium and large breeds.
Skin cancer doesn’t have one single appearance.
Changes to look out for include:
These changes can be black, brown, grey, pink or red. Any new lump, or an existing one that changes in size, shape or colour, should be checked by your vet.
Not all skin cancers are linked to sun exposure, but sunlight can increase the risk of squamous cell carcinoma, particularly in dogs with pale skin or sparse fur. Sunburn at any point in a dog’s life may increase this risk.
Genetics also appear to play a role, with certain breeds being more susceptible to specific tumour types.
Sunburn in dogs may cause:
Commonly affected areas include the nose, ear tips, belly, inner thighs, lips and any areas with little pigmentation or fur.
Reducing sun exposure is the best way to protect your dog from sunburn and sun-related skin cancers. Keeping dogs indoors or in the shade during peak UV hours (usually between 10am and 3pm) can help.
For dogs at higher risk, a pet-safe sunscreen can be useful. Always choose a product made specifically for dogs and follow the instructions carefully.
If your vet is concerned about a lump or skin change, they may take a small sample of cells using a fine needle or recommend a biopsy. These samples are examined under a microscope to determine whether the growth is cancerous.
In some cases, a surgical biopsy may be needed to reach a clear diagnosis. Your vet will talk you through the options and what’s best for your dog.
Many skin cancers can be treated successfully, particularly when caught early. Surgery to remove the lump is often the main treatment and can be curative in many cases.
Depending on the type and stage of cancer, radiotherapy or chemotherapy may also be considered. These treatments aren’t suitable for every dog, especially older pets or those with other health concerns, so decisions are always made with your dog’s comfort and quality of life in mind.
The outlook varies depending on the type of skin cancer and how early it’s diagnosed. Thankfully, many dogs go on to make a full recovery and enjoy a normal, happy life after treatment.
If you ever notice a new lump, sore or skin change on your dog, don’t ignore it. Your vet is there to help, and early advice can make all the difference.
