You notice a skin lesion on your dog. Could it be skin cancer? Learn why skin cancer in dogs might occur, what it looks like, what treatment is possible, and steps for preventing it in the first place.
woman with light pigmented dog outdoors; skin cancer in dogs
Credit: Rushay Booysen / EyeEm / Getty

The threat of skin cancer has many of us carefully applying sunscreen and watching out for any odd spots or growths that could signify the signs of this common and sometimes deadly form of cancer. But humans aren't the only ones who need to keep a close watch on our skin—dogs can be affected by skin cancer, too. And since our canine companions are often out in the sun alongside us, it's important to find out how and why skin cancer affects dogs, and what steps we can take to help prevent skin cancer in dogs. 

How Do Dogs Get Skin Cancer?

It is possible for dogs to get skin cancer. But why, exactly, is a bit of a mystery. Michael Childress, DVM, MS, DACVIM, and Head of the Oncology Section at Purdue University's College of Veterinary Medicine says the cause of most skin cancers in dogs is unknown. "However, just as is true in people, excessive exposure to ultraviolet (UV) light from the sun is linked to the development of some skin cancers in dogs. These include squamous cell carcinoma and cutaneous hemangiosarcoma."

Aside from sun exposure, another possible cause for squamous cell carcinoma in dogs is infection with canine papillomavirus, or warts, Childress says. Although there is a vaccine for human papillomavirus that prevents cancers associated with this virus, Childress notes there is not a vaccine that exists for canine papillomavirus, and that cancers induced by canine papillomavirus are not common.

What Does Skin Cancer Look Like in Dogs?

Just as we watch for odd occurrences on our skin, Childress says the most obvious sign of skin cancer in dogs is a mass or tumor growing on the skin. But there is some good news: He says about 50 to 70 percent of skin tumors in dogs are benign.

Childress says there are some factors that can help pet parents be on the lookout for skin cancer early on, like types of dog breeds. "Specific breeds tend to be predisposed to specific types of cancer rather than predisposed to skin cancer in general," he says, including boxers, Boston terriers, and pugs. Those breeds, Childress says, "are at higher risk for mast cell tumors than other breeds." Poodles, on the other hand, have a higher risk of squamous cell carcinoma.

A dog's age can also be a factor in whether or not he gets skin cancer, but not always. "Skin cancers, like most other cancers, tend to be diagnosed in older dogs. However, in rare cases, skin cancers can be identified in young dogs, including dogs under a year of age," Childress says.

When Should Take Your Dog to the Vet for Skin Issues?

If you've noticed a new area on your dog's skin that you suspect might be a tumor or lesion, Childress says a few things can help you gauge your level of worry. "Benign tumors tend to grow to a certain size and then stop growing, are usually small, and generally do not seem to bother most dogs," he says. "Signs that a skin tumor might be cancerous include rapid or persistent growth, redness, itchiness, bleeding, or feeling attached to tissues underneath this skin."

If you suspect that your pup's skin condition or growth is concerning, call your veterinarian to set up an examination. 

Is it Possible to Treat Skin Cancer in Dogs?

If your veterinarian diagnoses your dog with skin cancer, usually surgical removal of the growth is recommended. Childress says cancers that are too large to be surgically removed or that have metastasized can sometimes be treated with radiation therapy or chemotherapy "in such a way that a dog's life is extended or its quality of life improved." Your veterinarian can help you navigate the right way to approach treatment.

There are other medical innovations that can help as well. "A newer therapy called electrochemotherapy is also useful for some skin cancers," Childress says. "In electrochemotherapy, an electric current is applied across a cancer at the same time that chemotherapy is given. The electric current improves penetration of chemotherapy into the cancer, thereby allowing the chemotherapy to kill the cancer more effectively." 

Can Skin Cancer on Dogs Be Prevented?

We humans luckily have SPF at our fingertips to block harmful UV rays, but that same sunscreen can be dangerous for your dog (though there are pet-specific sunscreens that can help keep your pet from getting sunburned). Childress says in order to prevent skin cancer, we have to know what causes it, "which is difficult since we don't know what causes most skin cancers." 

One step is to consider those dogs who are more highly at risk. "Breeds of dogs with thin hair and lightly pigmented skin (e.g. greyhounds, whippets, beagles, white boxers, and pitbull terriers) are at increased risk for developing cancers caused by UV light, such as squamous cell carcinoma or hemangiosarcoma," Childress says. "These cancers tend to form on the areas of the body where the hair coverage is thinnest, like the underside of the belly and the insides of the thighs. Dogs that develop these cancers often have a history of sunbathing while rolled over on their backs. Discouraging this type of behavior is an effective way of preventing these skin cancers." 

Knowing it's possible for dogs to develop skin cancer, if you ever see a suspicious new growth on your dog's skin, make an appointment with your vet, because as with all health issues, early diagnosis is the key to a more successful outcome.