Mouth Cancer (Chondrosarcoma) in Dogs

Although mouth cancer is a common form of cancer in dogs (approximately 6%) and chondrosarcoma is common in other places of the body (about 5% - 10%), an oral chondrosarcoma is an uncommon form of the disease. It is more common to find chondrosarcoma that originated in the ribs, nasal, or pelvic areas. While oral chondrosarcoma may be rare, it seems to be on the rise, with an increase of about 30% in the numbers diagnosed in the past ten years. The cause of this increase is unknown, but veterinary medical professionals believe it is a combination of longer lifespans of dogs, and exposure to toxic chemicals. Primary oral chondrosarcoma is aggressive but moves slowly. Secondary oral chondrosarcoma is most often an aggressive fast mover, but this can vary depending on the area it spread from and how far advanced the disease is.

Mouth cancer (oral chondrosarcoma) is an oral form of bone cancer that causes neoplastic tumors in the cartilage. There are two types of chondrosarcoma, which are primary (originating in the mouth) and secondary (originating in another area). This form of bone cancer can metastasize (spread) anywhere in the body including the nose, eyes, ribs, pelvic area, and vital organs, but it moves slowly. Oral chondrosarcoma is characterized as a large (2cm - 20cm) solid mass that has ragged and undefined borders.

Oral chondrosarcoma is such a rare disease that little is known about it and that includes the warning signs. Unfortunately, finding and treating the cancer early is essential to a successful recovery. There are two types of oral chondrosarcoma with different symptoms:

Primary Chondrosarcoma

• Large and hard mass in or around the mouth or nose
• No pain
• Coughing 
• Sneezing
• Drooling
• Bad breath
• Difficulty swallowing
• Weakness
• Deformity of the face

Secondary Chondrosarcoma (depends on where the cancer originates)

• Limping
• Swelling of the affected area
• Painful hard lump
• Loss of weight
• Lethargy
• Runny nose/bloody nose
• Coughing
• Breathing difficulty 
• Extreme sleepiness

Types

• Primary oral chondrosarcoma is a type of cancer that originates in the mouth
• Secondary oral chondrosarcoma is cancer that has spread from another area of the body

The majority of primary oral chondrosarcomas have no known cause and just develop from healthy cartilage.Secondary oral chondrosarcoma spreads from another place in the body. 

Primary Oral  Chondrosarcoma

• Unknown 
• Large breed dogs such as the German Shepherd and Boxer are more commonly affected by oral chondrosarcoma 
• Middle to old age (5 years or older)
• Males are almost twice as likely to get oral chondrosarcoma

Secondary Oral Chondrosarcoma

• Spreads from another area of the body

The correct diagnosis of chondrosarcoma is usually pretty easy to determine by a veterinarian, but first a complete physical examination must be done. The veterinarian (or assistant) will get your dog’s vitals (weight, body temperature, heart rate, oxygen level, blood pressure, and reflexes. They will examine your dog’s mouth and throat with detailed precision to determine the size and structure of the tumor. A digital radiograph (x-ray) of the mouth, neck, chest, and head will need to be done to help the veterinarian get a clearer picture of the extent of the tumors. This will give the veterinarian a better idea of how far the oral sarcoma has spread and whether it is primary or secondary. In some cases, the veterinarian may need to get a CT scan, ultrasound, and MRI for details that cannot be seen on the x-rays. 

Some lab tests will need to be performed as well, such as blood work (CBC, blood gases, blood chemistry panel), urinalysis, oral swab culture, fine needle aspiration, and a biopsy of the tumor. With the test results, the veterinarian will be better able to decide on a form of treatment.

At this time, the only effective treatment available is surgery to remove the tumor and any questionable areas around the tumor. Oral chondrosarcoma does not respond to chemotherapy and radiation is only slightly effective, although there have been some cases of radiation therapy that are curative. The best choice remains to be surgery, and it is not always a permanent cure because oral sarcoma has a tendency to return.

Since chemotherapy and radiation are not good choices for treatment, the prognosis for oral chondrosarcoma is not very good. Surgery can remove any visible tumors, and if the disease has not spread, it is possible your dog can go into remission and live happily for the next couple of years. If the disease has spread, your dog may not have much more time and the best choice is to provide rest and pain medication to keep him comfortable as long as possible.