Oral Tumours - Papillomas and Fibropapillomas ('Sarcoids')

These notes are provided to help you understand the diagnosis or possible diagnosis of cancer in your pet. For general information on cancer in pets ask for our handout “What is Cancer”. If not already performed your veterinarian may suggest certain tests to help confirm or eliminate the diagnosis, and to help assess treatment options and likely outcomes. Because individual situations and responses vary, and because cancers often behave unpredictably, science can only give us a guide. However information and understanding of tumours in animals is improving all the time.

We understand that this can be a very worrying time and we apologise for the need to use some technical language. If you do not understand anything, please do not hesitate to ask.

mouth of dog and catsWhat are papillomas and sarcoids?

Oral papillomas are benign tumours of the epithelial lining of the mouth and throat caused by papillomaviruses. The viruses are specific for that species of animal and fairly site specific but can be transmitted to skin or eyes if the protective outer epithelium is damaged. The incubation period is approximately one month and recovery is within 2-3 months with immunity to further infection. The oesophagus (tube connecting the throat and stomach) may also be affected. A few tumours that look clinically similar are malignant cancers of the same epithelium (squamous cell carcinoma) with invasion and destruction of the underlying bone.

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 tumours on the face which we now know are caused by a special type of papillomavirus. These tumours disappear spontaneously but occasionally recur.

Rarely, puppies may have contact with a sheep pox virus that causes ‘contagious pustular dermatitis’ or “orf” and papillomatous masses may result in these pups. The tumours usually disappear spontaneously. Pox viruses are not species specific and this virus may infect people.

What do we know about the cause?

The reason why a particular pet may develop this, or any cancer, is not straightforward. Cancer is often seemingly the culmination of a series of circumstances which come together for the unfortunate individual.

These tumours are probably all associated with virus infections. Papilloma viruses cause most of these but there may be a role for other viruses in cats. Some papilloma viruses specific to people are associated with malignant cancers (the best known probably being cervical cancer in women).

Why has my animal developed this cancer?

Your pet has been infected with a virus.

Are these common tumours?

Oral papillomas are cauliflower-like lesions that are common in young dogs. Papillomas and fibropapillomas (sarcoids) are rare in cats.

How will this cancer affect my pet?

These tumours are usually noticed as single or multiple polypoid swellings on the gums or other parts of the mouth. Some ulcerate and bleed and they may become secondarily infected. Tumours in the throat (pharynx) are painful and may cause difficulty in swallowing.

x-ray machineHow is this cancer diagnosed?

Clinically, these tumours often have a fairly typical appearance. Radiography (x-rays) may be useful in detecting the few that are malignant, (invasive squamous cell carcinomas) because they destroy adjacent bone.

Cytology, the microscopic examination of small samples of cells, rarely helps in the diagnosis of these tumours. Definitive diagnosis, prediction of behaviour (prognosis) and a microscopic assessment of whether the tumour has been fully removed rely on microscopic examination of tissue (histopathology). This is done at a specialised laboratory by a veterinary pathologist. The piece of tissue may be a small part of the mass (biopsy) or the whole lump but only examination of the whole lump will indicate whether the cancer has been fully removed. Histopathology also rules out other cancers.

What types of treatment are available?

Surgical removal is the standard method of treatment for all these tumours but they will also disappear spontaneously. Removal at too early a stage may be counterproductive because the antigen from the papilloma cells that is needed to stimulate protective immunity is not produced until about a month after infection. Reducing inflammation and pain may give symptomatic relief.

Can this cancer disappear without treatment?

These viral cancers can disappear spontaneously in healthy animals due to the activity of the body’s immune system.

How can I nurse my pet?

After surgery, you will probably be provided with an “Elizabethan collar” to prevent your pet from interfering with the operation site. You may be requested not to examine the surgery but inability to eat or significant swelling or bleeding should be reported to your veterinarian. Your pet may require a special diet. If you require additional advice on post-surgical care, please ask.

How will I know how this cancer will behave?

Histopathology will give your veterinarian the diagnosis that helps to indicate how it is likely to behave. The veterinary pathologist usually adds a prognosis that describes the probability of local recurrence or metastasis (distant spread). The completeness of excision will be assessed and other diagnoses ruled out.

microscopeWhen will I know if the cancer is permanently cured?

“Cure” has to be a guarded term in dealing with any cancer.

Most of these tumours are permanently cured by surgery or the body’s own immune system. If there is recurrence, it may indicate the tumour was incompletely removed, is deeper and more malignant (papillomatous squamous cell carcinoma) or the immune system is not fully competent.

Are there any risks to my family or other pets?

These are infectious tumours. With the exception of the rare pox virus infection of contagious pustular dermatitis (‘orf’), transmission from one pet to another is within the same species and requires close contact, damage to the surface of the mouth or lips and lack of immunity (either because the animal has not encountered the virus or because it lacks a fully competent immune system). The tumours are not transmitted from pets to people.

This client information sheet is based on material written by: Joan R. Rest, BVSc, PhD, MRCPath, DipECVP, MRCVS. RCVS

Adapted by Philip H Brain, BVSc, CMAVA, FACVSc (small animal medicine), FAVA © Copyright 2015 LifeLearn Inc. Used and/or modified with permission under license.