Tonsillar Squamous Cell Cancer in Dogs

Last Modified: September 25, 2005

Dear OncoLink "Ask The Experts,"
I have 8-yr-old English Springer spaniel that was just diagnosed with anaplastic tonsillar squamous cell carcinoma with metastasis to a submandibular lymph node. Can you send me info regarding this disease, and if there is any form of radiation or other therapy?

Lili Duda, VMD, Section Editor of the OncoLink Veterinary Oncology Menu, responds:

Squamous cell carcinoma of the tonsil is a very aggressive cancer in dogs. As tonsillar squamous cell carcinoma progresses, it is typically locally invasive into the tonsil and surrounding tissues, including the larynx, and often metastasizes (spreads) fairly early into the draining submandibular and retropharyngeal lymph nodes, then to the lungs, and then possibly elsewhere.

Sometimes the initial finding is a large submandibular lymph node that is found to contain squamous cell carcinoma, and the primary tonsillar mass is still quite small relative to the enlarged lymph node. In other cases, the dog presents with signs attributable to a large mass at the back of the mouth, such as change or loss of bark, noisy breathing, increased snoring, and difficulty swallowing. In those cases in which it is possible to surgically remove the primary tonsillar mass and affected lymph nodes (and there is no evidence of spread to the lungs or elsewhere), the surgery should be followed up with radiation therapy to the surgical field, and chemotherapy to try and prevent or delay the development of any distant metastases.

In those cases where surgery is not possible, palliative radiation therapy can often provide improvement in clinical signs for a period of months. It is unclear how much chemotherapy contributes to the palliative radiation regimen. The non-steroidal anti-inflammatory drug (NSAID) piroxicam has been shown to provide some benefit in these cases, both by decreasing swelling and inflammation around the tumor, as well as having specific anti-tumor activity against squamous cell carcinoma.

Please see this article on piroxicam for more information.