Oral Tumors in Dogs - Fibrosarcoma

What are oral fibrosarcomas?

Oral fibrosarcomas are rapidly growing, malignant tumors originating from the fibrous connective tissue of the mouth and may be cured by surgical removal. Recurrence in the mouth and spread to other parts of the body (metastasis) are common.

How are oral tumors caused?

Although the exact cause is unknown, cancer is often the culmination of many factors including heredity, diet, and environment.

Why has my dog developed fibrosarcoma?

Some breeds have a greater tendency (genetic susceptibility) to develop cancer. With fibrosarcoma, the Golden Retriever’s upper jaw is commonly affected.

Are fibrosarcomas common?

In dogs, oral fibrosarcomas represent between 17 percent and 26 percent of all mouth tumors. A quarter of these tumors are recorded in dogs less than five years of age, with some even occurring in dogs less than a year of age. Larger dogs, particularly Golden Retrievers, are more predisposed to develop fibrosarcomas than smaller breeds. Tumors are also more common in male dogs and can occur on the palate (roof of the mouth) and, occasionally, in the tongue.

"In dogs, oral fibrosarcomas represent
between 17 percent and 26 percent of all
mouth tumors."

How will fibrosarcoma affect my dog?

Fibrosarcoma tumors usually appear as swellings on the gums. They frequently ulcerate and bleed, and may become secondarily infected, causing a foul odor. Other common clinical signs include drooling, difficulty eating, displacement or loss of teeth, facial swelling, and painful swelling of the local lymph nodes.

Fibrosarcoma upper jawHow is an oral fibrosarcoma diagnosed? 

Swelling on the gums or hard palate is common and noticeable, while X-rays may be used to detect whether the tumor has invaded the bones and to guide surgical decisions. If there’s bone loss adjacent to the tumor, the prognosis is usually poor as malignant gum tumors destroy bone; benign tumors tend to make the adjacent bone grow.

An accurate diagnosis of fibrosarcoma tumors requires microscopic examination of tumor tissue. Cytology, the microscopic examination of cell samples, is not usually diagnostic for these tumors.

For a definitive diagnosis, prediction of behavior (prognosis) and an assessment of the completeness of tumor removal, veterinarians will rely on the results of a microscopic examination of tissue (histopathology). Your veterinarian will submit either a small part of the mass (biopsy) or the whole mass 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.

"An accurate diagnosis of fibrosarcoma
tumors requires microscopic examination
of tumor tissue."

Most fibrosarcomas invade the jaw bone. For complete removal, they need wide surgical margins usually including substantial parts of the jawbone. Tissue samples that contain bone will need decalcifying, so it may take a few weeks before the final histopathology results are available.

What types of treatment are available?

Surgical removal is the standard method of treatment for all oral tumors. If the tumor is invasive, it may be difficult to remove completely so large pieces of the adjacent jawbone may need to be removed. Dogs respond well to this type of surgery. If your dog requires one of these complex and extensive surgeries, your veterinarian may refer you to a specialist.

"Surgical removal is the standard method
of treatment for all oral tumors."

Fibrosarcomas do not respond to chemotherapy and there’s only a short-term response to radiotherapy.  

 Swelling of the face due to tumor    After surgery, swelling subsided

Can this cancer disappear without treatment?

Treating infections and healing ulcers will help reduce swelling, but it will not cure the cancer. The body's immune system is not effective at making these tumors regress.

How will I know how this cancer will behave?

The histopathology report indicates how it 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 fibrosarcoma is permanently cured?

Major, radical surgery can result in tumor-free time for as long as 32 months, although the median survival is seven months and about half of all cases will survive beyond one year. Fibrosarcomas located closer to the front of the mouth are usually easier to treat and have a better prognosis.

Are there any risks to my family or other pets?

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

This client information sheet is based on material written by: Jan Bellows, DVM, Dipl. AVDC, ABVP

© Copyright 2013 LifeLearn Inc. Used and/or modified with permission under license.

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