What are oral tumors?
The oral cavity (mouth) is a common site for a variety of tumors, both benign (noncancerous) and malignant (cancerous).
The most frequent benign oral tumors are
epulides, firm masses involving the gingival tissue (gums). In dogs, the most
common malignant oral tumors are (in decreasing order):
oral melanoma, oral squamous cell carcinoma, and oral
fibrosarcoma. Less common malignant oral tumors in dogs include osteosarcoma, chondrosarcoma, anaplastic sarcoma,
intraosseous carcinoma, myxosarcoma, hemangiosarcoma, lymphoma, mast cell tumor, and multilobular tumor of bone.

In cats, squamous cell carcinoma (SCC) is the most common oral cancer, followed by oral fibrosarcoma. To learn about
diagnosis and treatment options specific to feline oral SCC, please click
here.

How common are oral tumors in cats and dogs?
Oral cancer accounts for approximately 6% of all cancers in dogs and is the fourth most common cancer overall. In cats, it
accounts for 3% of all cancers. Oropharyngeal (oral cavity and pharynx) cancer is 2.6 times more common in dogs
compared to cats, and male dogs have a 2.4 fold greater risk of developing oral cancer compared to female dogs. Dogs
with heavily pigmented oral mucosa, such as chow chows, are at increased risk of developing oral melanoma. Squamous
cell carcinoma and fibrosarcoma are more commonly seen in large-breed dogs. The median age for developing oral
melanoma is 11-12 years, 8-10 years for squamous cell carcinoma and 7-9 years for fibrosarcoma.

What are the symptoms of oral tumors in cats and dogs?
Most cats and dogs with oral cancer have a mass in the mouth noticed by the owner but tumors are rarely seen by the
owners in the pharynx. Pets with oral tumors have symptoms of increased salivation (drooling), facial swelling, mouth
bleeding, 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 tumors made?
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
biopsy 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 to 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. For small lesions (e.g. epulides, papillomas, or small labial mucosal melanoma), excisional biopsy (surgical
removal of the lesion followed by microscopic analysis) may be an option.

Below are examples of malignant oral tumors in dogs.












Does cancer cause pain in cats and dogs?
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 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 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 and prognosis for oral cancer in cats and dogs?
To learn about treatment options and prognosis for specific subtypes of oral tumors, please click on the appropriate
section below:

Oral melanoma
Oral squamous cell carcinoma (dogs)
Oral squamous cell carcinoma (cats)
Oral fibrosarcoma
Oral epulides

Where 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 or to provide you with a second opinion, please visit the "
Locate a veterinary oncologist" section.  

Additional online resources

Sources:
© 2007 Pet Cancer Center. ALL RIGHTS RESERVED.
Last updated 4/10/13
Oral Cancer (Mouth Tumors) in Cats and Dogs
Oral melanoma
Squamous cell carcinoma
Oral fibrosarcoma
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PET CANCER CENTER
Comprehensive guide to cancer diagnosis and treatment in cats and dogs