Oral Tumors: Papillomas and Sarcoids

NOTE: When it comes to cancer, your veterinarian may suggest certain tests to help confirm or eliminate diagnosis, and to help assess treatment options and likely outcomes. Because individual situations and responses vary, and because tumors often behave unpredictably, science can only give us a guide. However, information and understanding about tumors and their treatment in animals is improving all the time.

What are papillomas and fibropapillomas?

"Oral papillomas (warts) are benign tumors of the epithelial lining of the mouth and throat."

Oral papillomas (warts) are benign, cauliflower-like tumors of the epithelial lining of the mouth and throat, although the esophagus may also be affected in severe cases. These tumors are caused by papillomaviruses. Papillomaviruses are species-specific and are fairly site-specific, but can be transmitted to the skin or eyes if the protective outer epithelium is damaged. The incubation period is approximately one month and recovery occurs within 2-3 months; after recovery, the pet will be immune to further infection. It is important to distinguish papillomas from other, malignant tumors that may also affect the mouth.

Fibropapillomas have more proliferation of the connective tissue adjacent to the epithelium and resemble "sarcoids" in horses. They may be multiple in the mouths of young cats and are similar to tumors on the face which we now know are caused by a special type of papillomavirus. These tumors disappear spontaneously but occasionally recur.

Rarely, puppies may have contact with a sheep-pox virus that causes “contagious pustular dermatitis” or "orf", and wart-like masses may appear in these pups. The tumors usually disappear spontaneously. Pox viruses are not species-specific and this virus may infect people.

Why has my pet developed a papilloma or fibropapilloma?

The reason why a particular pet may develop this, or any tumor, is not straightforward. Tumors are often the culmination of a series of circumstances that come together for the unfortunate individual. However, these tumors are probably all associated with virus infections. Papillomaviruses cause most of these tumors, but other viruses may play a role in cats. Some papillomaviruses specific to people are associated with malignant cancers (the best known probably being cervical cancer in women).

Are these common tumors?

Oral papillomas are common in young dogs. Papillomas and fibropapillomas (sarcoids) are rare in cats.

How will this cancer affect my pet?

These tumors are usually noticed as single or multiple polyp-like swellings on the gums or other parts of the mouth. Some ulcerate and bleed and they may become secondarily infected. Papillomas in the throat (pharynx) or esophagus are painful and may cause difficulty in swallowing.

How are papillomas and fibropapillomas diagnosed? 

Clinically, these masses often have a fairly typical appearance. Radiographs (x-rays) may be useful in differentiating them from malignant tumors such as invasive squamous cell carcinomas, because the invasive cancers will destroy adjacent bone.

Accurate diagnosis of papillomas and fibropapillomas requires microscopic examination of the tissues. Cytology, the microscopic examination of small samples of cells obtained with a needle, rarely helps in the diagnosis of these tumors. Definitive diagnosis, prediction of behavior (prognosis), and an assessment of the completeness of removal typically requires a biopsy Histopathology also rules out other, more malignant cancers. Your veterinarian will submit either a small part of the mass (biopsy) or the whole lump to a specialized diagnostic laboratory, where a veterinary pathologist will examine and diagnose the lesion.

What types of treatment are available?

Surgical removal is the standard method of treatment for these tumors. Since they will also disappear spontaneously within a few months, surgical removal is recommended for diagnostic purposes (to ensure that the mass is a benign "wart"), or to treat a bleeding or infected growth. Removal at too early a stage may be counter-productive because the antigen from the papilloma cells (needed to stimulate protective immunity by the patient) is not produced until about a month after infection. If surgery is not performed, medication to reduce inflammation and pain may give symptomatic relief. Immune stimulating medications such as interferon alpha or imiquimod (Aldara®) may also be used.

Can papillomas and fibropapillomas disappear without treatment?

These viral tumors can disappear spontaneously in healthy animals due to the activity of the body's immune system. Occasionally, fibropapillomas may recur.

How can I nurse my pet?

After surgery, your pet will need to wear an Elizabethan collar (E-collar or cone) to prevent trauma to the operation site. Your pet may require a special diet. Your veterinarian may request that you do not try to examine the surgery site in the early post-operative period. If your pet is unable to eat or develops significant swelling or bleeding at the surgical site, contact your veterinarian immediately. If you require additional advice on post-surgical care, please ask.

How will I know how this cancer will behave?

The histopathology report will give your veterinarian a diagnosis that helps to indicate how the tumor is likely to behave, and rules out other, more malignant cancers. The veterinary pathologist usually adds a prognosis that describes the probability of local recurrence or metastasis (distant spread). 

When will I know if the cancer is permanently cured?

Most of these tumors are permanently cured by surgical removal or by the body's own immune system. If there is recurrence, it may indicate the tumor was incompletely removed, that it is deeper and more malignant (papillomatous squamous cell carcinoma), or that the pet's immune system is not fully competent.

Are there any risks to my family or other pets?

"These are infectious tumors....The tumors are not transmitted from pets to people."

These are infectious tumors. With the exception of the rare sheep-pox virus infection of contagious pustular dermatitis, these tumors are species-specific. Transmission occurs between animals within the same species and requires close contact with an infected pet, damage to the surface of the mouth or lips, and a lack of immunity (either because the animal has not encountered the virus or because it lacks a fully competent immune system). The tumors are not transmitted from pets to people.