Papillomaviruses (PVs) are viruses that infect the skin and mucous membranes. Canine papilloma virus (CPV) infections commonly result in warts known as papillomas. Papillomas can appear on your dog’s skin or in the mucous linings, including the mouth, nose, eyelids, lungs, digestive tract, and urinary tract. In dogs, papillomas appear to have a rough surface that resembles a cauliflower or a sea anemone. Not all CPV infections cause papillomas; your dog may carry this virus without clinical signs. If you have a puppy, an older dog, or a dog with a weakened immune system, they may be at risk of developing papilloma warts. In a healthy dog, the immune system fights the disease by producing antibodies against CPV, which can mean your dog will not have papillomas or other symptoms.

How does a papilloma turn into a tumor?

In humans, there is a well-established link between human papilloma virus (HPV) and malignancies such as cervical cancer. In dogs, the role of CPV in the development of cancerous lesions is not entirely understood. Reports suggest that papillomas may turn cancerous if a dog has a poor immune response to the CPV infection. A more severe illness may result, with the potential to cause serious dysregulation in cell growth and division. CPV infection may “turn on” genes associated with cancer progression (known as oncogenes) and “turn off” genes that protect against cancer development (known as tumor suppressors).

It is unlikely that a healthy dog will develop a tumor following a CPV infection but understanding the associated risks will help you make the best decisions for your pet’s health.

How does CPV increase cancer risk in dogs? 

Numerous studies have reported that papillomaviruses can cause benign tumors in dogs. While many cases of CPV result in benign skin lesions, CPV infections can also be associated with cancers such as squamous cell carcinoma (SCC). SCC is a type of skin cancer that can occur anywhere on your dog’s skin, including the paws and nail beds, and inside their mouth and nose. In healthy dogs, papillomas generally do not spread around the body. However, severe CPV infections in dogs with a compromised immune system may result in metastatic SCC that can spread beyond the primary tumor to the lungs, liver, and bone.

If the SCC growth is on your dog’s skin, the best and most common treatment is surgery to remove the tumor. Sometimes complete tumor removal isn’t possible. In these cases, radiation therapy is used in addition to surgery because SCC may not respond well to chemotherapy.

If your vet diagnoses your dog with CPV, discuss the extent of the infection and learn about the treatment options. Your vet can help you find a course of treatment that best suits you and your dog

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Last Updated: September 16, 2021

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The following sources were referenced to write the content on this page:

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Ghim, S, Newsome, J, Bell, J, Sundberg, JP, Schlegel, R & Jenson, AB 2000, ‘Spontaneously regressing oral papillomas induce systemic antibodies that neutralize canine oral papillomavirus’, Exp Mol Pathol, vol. 68, no. 3, pp. 147-151.

Meuten, DJ 2002, Tumors in Domestic Animals, 4 edn, Blackwell Publishing, Ames, Iowa.

Munday, JS, Thomson, NA & Luff JA 2017, ‘Papillomaviruses in dogs and cats., Vet J, vol. 225, pp. 23-31.

Munday, JS, Tucker, RS, Kiupel, M & Harvey, CJ 2015, ‘Multiple oral carcinomas associated with a novel papillomavirus in a dog’, J Vet Diagn Invest, vol. 27, no. 2, pp. 221-225.

Nicholls, PK & Stanley, MA 2000, ‘The immunology of animal papillomaviruses’, Vet Immunol Immunopathol, vol. 73, no. 2, pp. 101-127.

The Pet Cancer Foundation’s medical resource for pet owners is protected by copyright.

For reprint requests, please see our Content Usage Policy.