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Oral Tumors - Epulis Basal Cell Carcinoma, Ameloblastoma

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". 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 cancers 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.

We understand that this can be a very worrying time. If you have any questions please do not hesitate to ask us.

 

What are these tumors?oral_tumors_epulis_basal_cell_carcinoma_ameloblastoma-1

Anepulis (plural epuli) is the clinical name for a swelling on the gums. Several different tumors share this name, often of different origins including the tooth-socket lining and lining epithelium of the mouth. Most epuli are not cancerous but overgrowths (hyperplasias) as a reaction to trauma. These are fibrous (fibrous hyperplasia orfibromatous epulis). If they are more active, often with bone formation, they are called peripheral odontogenic fibroma (POF) or fibromatous and ossifying epulis). These originate from the tooth forming tissue. A few of this type are cancerous but benign. Occasionally, these become more malignant and invade locally. Rarely, there is spread to lymph nodes as fibrosarcomas.

Cancers that are more aggressive and invade the bone of the jaws include basal cell carcinomasthat originate from the epithelium of the gum surface and a tumor of tooth (odontogenic) epithelium called ameloblastoma or adamantinoma. Other types of very rare tumors that arise from the tooth tissues include amyloid producing 'odontogenic' or calcifying epithelial odontogenic tumor. These other tumors tend to recur after surgery.

 

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 the culmination of a series of circumstances that come together for the unfortunate individual.

Most epuli are hyperplasias (overgrowth) as a reaction to trauma. Cancer is essentially the result of non-lethal genetic damage to cells with "external" contributory factors that may be chemical, physical and/or traumatic. The mutated cells upset the normal regulation of cell death and replacement. They do this by activating growth-promoting oncogenes (cancer genes), inactivating suppressor genes and altering the genes that regulate normal, programmed cell death (apoptosis).

 

Why has my pet developed this cancer?

"Multiple extensive gingival hyperplastic lesions occur mainly in Boxers and other short-nosed breeds."

Some animals have a greater tendency (genetic susceptibility) to cancer. Some breeds have far more cancers than others, often of specific types. Multiple extensive gingival hyperplastic lesions occur mainly in Boxers and other short-nosed breeds.

 

Are these common tumors?

"The non-cancerous epuli are common in older dogs but rare in cats."

The non-cancerous epuli are common in older dogs but rare in cats. Some dogs, particularly Boxers and other short-nosed dogs have multiple growths called 'gingival hyperplasia'. This is present in almost a third of Boxers. Basal cell carcinomas are far less common. Ameloblastomas are unusual in dogs and even rarer in cats. They can occur at any age.

 

How will these tumors affect my pet?

These tumors are usually noticed as swellings on the gums around the teeth. They frequently ulcerate and bleed, and may become secondarily infected. Other common clinical signs include drooling saliva, difficulty in eating, displacement or loss of teeth and facial swelling. Epuli are rarely painful.

 

How are these tumors diagnosed?

Clinically, the tumors often have a typical appearance. X-rays may be useful to detect whether tumors have invaded the bones and to guide surgery. Loss of bone adjacent to the tumor usually means a poorer prognosis because malignant gum tumors destroy bone whereas benign ones tend to make the adjacent bone grow.

"Malignant gum tumors destroy bone whereas benign ones tend to make the adjacent bone grow."

Accurate diagnosis of these tumors requires microscopic examination of tumor tissue. Cytology, the microscopic examination of small cell samples, is not diagnostic for these tumors. Definitive diagnosis, prediction of behavior (prognosis) and an assessment of the completeness of tumor removal rely on microscopic examination of tissue (histopathology). Histopathology also rules out other cancers. Your veterinarian will submit either a small part of the mass (biopsy) or the whole lump to a specialized laboratory, where a veterinary pathologist will examine and diagnose the lesion. If your veterinarian submits the entire mass, the pathologist may be able to indicate whether the cancer has been completely removed.

Sixty percent of epuli have bone in them. Although this does not affect behavior, the tissue sample may need decalcifying before it examination, delaying the final histopathology report on the tumor.

 

What types of treatment are available?

Surgical removal is the standard treatment for all oral tumors. If the tumor is invasive, it may be difficult to remove completely, and it may be necessary to remove a large piece of the jawbone (hemimaxillectomy or hemimandibulectomy). Dogs (particularly when young) respond well to this radical surgery. If your pet requires one of these complex and extensive surgeries, your veterinarian may refer you to a specialist at a veterinary referral center.

 

Can these cancers disappear without treatment?

If the epuli formed as reactions to trauma, they may reduce in size if the stimuli are removed. Treating secondary infections and healing ulcers will help reduce inflammation. Basal cell carcinomas and ameloblastomas are more aggressive and do not disappear. Very occasionally, spontaneous loss of blood supply to the cancer can make parts of it die but the dead tissue will still need surgical removal. The body's immune system is not effective at making these tumors to regress.

 

How can I nurse my pet?oral_tumors_epulis_basal_cell_carcinoma_ameloblastoma-2

After surgery, your pet will need to wear an "Elizabethan collar" to prevent damage to the surgical site. If your pet also requires a special diet, this will be discussed with you. Your veterinarian may request that you do not try to examine the surgery site in the early post-operative period. However, if your pet is unable to eat or develops significant swelling or bleeding, you need to contact your veterinarian immediately. If you require additional advice on post-surgical care, please ask.

 

How will I know how these tumors will behave?

"The histopathology report will give your veterinarian the diagnosis that helps to indicate how the tumor is likely to behave."

The histopathology report will give your veterinarian the diagnosis that helps to indicate how the tumor is likely to behave. The veterinary pathologist usually adds a prognosis that describes the probability of local recurrence or metastasis (distant spread) and, if the entire mass was submitted for examination, will usually assess the completeness of excision.

 

When will I know if the cancer is permanently cured?

'Cured' has to be a guarded term in dealing with any cancer.

Epuli rarely recur if the cause of the proliferation and inflammation is removed. A few of the most active ones do regrow and require more extensive surgery. This may be indicated in the histopathology report.

Basal cell carcinomas recur in about half the cases with significant bone destruction and tooth loss. Ameloblastomas also tend to recur and invade and destroy bone. Both will need extensive surgery for complete cure but they do not metastasize to other parts of the body. Survival for more than a year is not uncommon after radical surgery.

A mildly guarded prognosis is usually suggested for all these tumors because they can be multiple. Occasionally the clinically apparent lump occurs above a different and more malignant tumor. A few epuli will progress to more invasive types. However, most of these gingival growths are benign.

 

Are there any risks to my family or other pets?

No, these are not infectious tumors and are not transmitted from pet to pet or from pets to people.

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

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