Fibrosarcomas are most commonly seen in the upper jaw (maxilla) but can also be present in the lower jaw (mandible).
Although locally invasive, these tumors have lower metastatic potential (spread to other organs) compared to oral
melanomas. Because these tumors tend to be locally invasive, recurrence (coming back) after surgery can be as high as

What are the symptoms of oral fibrosarcomas in cats and dogs?
Most cats and dogs with oral cancer have a mass in the mouth noticed by the owner. Pets with oral tumors will typically have
symptoms of increased salivation (drooling), facial swelling, mouth bleed, weight loss, foul breath, oral discharge, difficulty
swallowing, or pain when opening the mouth. Loose teeth could be indicative of bone destruction due to the tumor.

How is the diagnosis of oral fibrosarcoma made in cats and dogs?
A thorough diagnostic evaluation of oral tumors is critical due to the variety of different tumors that could be present.
Sedation or anesthesia is often required in order to examine the pet's mouth, especially if the suspected tumors are located
in the back of the mouth or on the tongue. If the tumor is suspected to be malignant, chest X-ray can be done prior to
to check for metastasis (spread) to the lungs. Bone destruction is not typically seen on X-rays of the mouth until >40% of the
bone is destroyed so what appears to be a normal X-ray cannot exclude the tumor's bone invasion.
Advanced imaging such
as CT (computed tomography) or MRI (magnetic resonance imaging) can be valuable tools in staging the disease
(determining how advanced it is), especially for evaluating bone invasion and tumor's potential extension into the nasal
cavity, pharynx or the eye. The use of CT may eliminate the need for regular X-rays but CT/MRI imaging is more expensive.

Regional lymph nodes should be carefully assessed for any abnormalities, although lymph node size is not an accurate
predictor of metastasis. In a study of 100 dogs, 40% showed normal sized lymph nodes despite being positive for cancer
cells, and 49% of dogs who showed lymph node enlargement did not actually have lymph node metastasis. Lymph node
aspirates (isolation of cells for microscopic analysis to check for the presence of any cancer cells) are, therefore,
recommended for pets with oral cancers.

The final diagnostic step, which is done under anesthesia, is a large incisional
biopsy. Biopsy is preferred over cytology to
definitively differentiate between benign (noncancerous) and malignant (cancerous) tumors and determine the exact type of
the tumor present. This is important in order to plan treatment that will best maximize the pet's response and survival.

Does cancer cause pain in pets?
Pain is common in pets with cancer, with some tumors causing more pain than others. In addition to pain caused by the
actual tumors, pets will also experience pain associated with cancer treatments such as surgery, radiation therapy or
chemotherapy. Untreated pain decreases the pet's quality of life, and prolongs recovery from the illness, treatment or injury.
It is, therefore, essential that veterinary teams that are taking care of pets with cancer should also play a vital role in
educating pet owners about recognizing and managing pain in their pets. The best way to manage cancer pain in pets is to
prevent it, a term referred to as preemptive pain management. This strategy anticipates pain ahead of time and administers
pain medication before the pet actually experiences pain, thus ensuring the pet's maximum comfort.

To learn more about which tumors are likely to cause a lot of pain, how to recognize pain in pets with cancer and what
cancer pain management options are available for your pet, please visit the
Cancer Pain Management section.

How important is nutrition for pets with cancer?
Cancer cachexia (a term referring to progressive severe weight loss) is frequently observed in pets with cancer. Pets with
cancer lose weight partly because of lack of appetite and partly because of cancer-induced altered metabolism. Some of the
causes for decreased appetite are related to the cancer itself (for example, tumors may physically interfere with food
chewing, swallowing, and digestion process) and some may be related to the side effects of cancer treatment (for example,
some chemotherapy drugs cause nausea and vomiting, and radiation therapy can cause mouth inflammation).

Proper nutrition while undergoing cancer treatment is essential to maintain your pet's strength, improve survival times,
quality of life and maximize response to therapy. Adequate nutritional support was shown to decrease the duration of
hospitalization, reduce post-surgery complications and enhance the healing process. Additionally, pets with cancer need to
be fed diets specifically designed to provide maximum benefit and nutritional support for the patient. To learn more, please
visit the
Cancer Nutrition section.

What are the treatment options for oral fibrosarcoma in cats and dogs?
Surgical removal of oral fibrosarcoma is the primary method of treatment whenever possible. The exact type and extent of
surgery depends on the tumor's size and location. If an aggressive surgery is needed, it may affect the cosmetic and
functional appearance of the pet; however, cosmetic appearance is generally good after most upper or lower jaw surgeries.
For an overview of the surgical treatment of oral cancers as well as possible post-surgery complications, please click

In 19 dogs whose oral fibrosarcoma in the lower jaw was removed by partial mandibulectomies (where part of the lower jaw
was removed), median survival time was 10.6 months (range 3-33 months), and 50% of dogs were alive after one year.
Twelve of the 19 dogs were euthanized due to recurrent or metastatic disease (
Kosovsky, Vet Surg, 1991). Other studies
showed that dogs with oral fibrosarcoma treated with surgery had median survival of 11 months.

In two studies reporting on outcomes in 29 dogs whose oral fibrosarcoma in the upper jaw was removed by surgery (where a
part of the upper jaw was removed), median overall survival was 9.5-12.2 months. Of these 29 dogs, 17 died due to their
disease and 14 (48%) had local recurrence. In a third study with 14 dogs treated with surgery for lower or upper jaw
fibrosarcoma, the one-year survival rate was 50%, local recurrence occurred in 36% of the dogs and 14% of the dogs
developed metastases.

In a more recent (2008) study of 38 dogs with oral fibrosarcoma treated with surgery alone, the dogs had median survival of
1024 days - much improved over earlier reports. It is thought that better imaging prior to surgery along with improved
techniques led to these outcomes.

Radiation therapy
Radiation therapy can be used as a primary treatment for oral tumors, with either the intention to cure or simply provide
relief, or in combination with surgery for tumors that were not completely removed by surgery. Oral fibrosarcomas are
generally considered to be resistant to radiation therapy so the use of radiosensitizers (drugs that make cancer cells more
sensitive to radiation) is a new way to try to improve the pets' response to radiation therapy.

In a study of 28 dogs with oral fibrosarcoma treated with radiation, the disease did not progress for 26 months. However, the
progression-free time period decreased as the stage (size) of the tumor increased: for dogs with T1 stage (tumors <2cm
diameter), median progression-free survival (PFS) was 45 months; for dogs with T2 stage (2-4cm in diameter), the PFS was
31 months; and for dogs with T3 stage (>4 cm in diameter), the PFS was 7 months. In a separate study of seven dogs
whose oral fibrosarcomas were treated with radiation therapy after surgery was not able to completely remove the tumors,
the median survival time was 18 months.

Chemotherapy is used for oral tumors that have a high metastatic potential, especially oral melanoma in dogs and tonsillar
squamous cell carcinoma in cats and dogs. Since oral fibrosarcomas are not generally metastatic, chemotherapy does not
play an important role in their treatment.

How do I find a qualified veterinary oncologist?
To locate a qualified veterinary oncologist worldwide who can discuss with you appropriate cancer treatment plan for your
pet's cancer condition, please visit the "
Locate a veterinary oncologist" section.  

Are there any clinical trials investigating new treatments for oral fibrosarcomas in cats and dogs?
There are several clinical trials ongoing for dogs with soft tissue sarcomas, which are partially funded by the institutions. To
learn more about these trials, please visit the
Clinical Trials for Soft Tissue Sarcoma in Dogs section.

Additionally, there are several clinical trials available for cats and dogs with any tumor type for which your pet may qualify.
To learn more these trials (which are partially or fully funded by the institutions), please visit the
Dog Clinical Trials (any
tumor type) or Cat Clinical Trials (any tumor type) section.  

To learn more about veterinary clinical trials in general, please visit the
Pet Clinical Trials section.

What is the prognosis for oral fibrosarcoma in cats and dogs?
Oral fibrosarcomas are very aggressive in local invasion. Combination therapies seem to best control the tumor such as
surgery with radiation therapy, or radiation therapy with hyperthermia.

Surgery is the most common treatment for oral fibrosarcoma; however, 1-year survival rates rarely exceed 50% with surgery
alone. The median survival of dogs with lower jaw surgery was ~11 months, local recurrence occurred in 59% of the dogs
and a 1-year survival rate was 50%. A similar outcome was observed with surgery of the upper jaw, with local recurrence in
~40% of dogs, and a median survival time of 12 months. Radiation alone offers median survival of only 7 months but
combination of surgery and radiation therapy offers the  best chance of controlling the tumor, with median survival time
increased to 18-26 months. Radiation therapy combined with regional hyperthermia has also shown to improve local control
rates. The size of the tumor plays a role in how well the pet will respond (dogs with smaller tumors live longer compared to
those with larger tumors).

  • Withrow Stephen J, and David M. Vail. Small Animal Clinical Oncology. St Louis: Saunders Elsevier, 2007.
  • Morrison Wallace B. Cancer in Dogs and Cats: Medical and Surgical Management. Baltimore: Williams&Wilkins, 1998.
Oral Fibrosarcoma in Cats and Dogs
© 2007 Pet Cancer Center. ALL RIGHTS RESERVED.
Last updated 2/19/2017
Comprehensive guide to cancer diagnosis and treatment in cats and dogs