Courtney before surgery. All the visible teeth in this photo define the area that was later removed; her lower jaw was amputated straight across behind the lower canine teeth. Photo courtesy of David Jensen of Alaska Pet-ography.
When squamous cell carcinoma occurs in the mouth and throat, it’s called oral squamous cell carcinoma. In these oral cases, the lesion is usually located on the gums or tonsils. In cats, SCC is the most common oral cancer. In dogs, SCC is the second most common oral tumor. SCC is the most common tongue tumor.
Signs can include drooling (with or without blood), difficulty eating, and halitosis (very bad breath). Depending on the tumor’s location, the pet can have trouble swallowing or may cough. If the mouth is too uncomfortable for the pet to eat normally, the animal will lose weight. As is true with many cancers, affected dogs and cats tend to be older animals.
Diagnostics include radiographs of the local site, radiographs of the lungs to see if it has spread (metastasized) to other locations, CT scans, biomarker assessment, and biopsies. Sometimes a fine needle aspirate will provide enough sample tissue for diagnosis. In a study of oral SCCs, biomarkers (proliferating cell nuclear antigen and Ki-67) were associated with higher grade tumors and increased likelihood of spread.
Treatment may involve surgery, radiation therapy, and/or chemotherapy. Treatment depends on location, the amount of tissue involved, etc.
If the tumor hasn’t spread, surgery is the preferred treatment. The entire tumor, including the extensions into underlying tissue and bone, will be removed. Often, part of the jawbone has to be removed. Surgery can provide a cure if the pet has clean margins (the tumor was completely removed). Dogs do quite well with partial jaws. Surprisingly enough, it doesn’t typically alter the dog’s appearance as much as you might expect. Even if surgery isn’t curative, surgery can extend survival.
Radiation therapy can be used if surgery isn’t an option, or if surgery can’t completely remove the tumor.
Chemotherapy may be added to therapy, depending on the circumstances.
Electromagnetic thermoablation (hyperthermia, in which body tissue is exposed to high temperatures) may be used. This technique applies a high-frequency alternating electromagnetic field to heat alloy needles. The needles are placed into and surrounding the tumor in order to destroy the malignant tissue.
Supportive therapy includes analgesics, acupuncture, feeding tubes to provide nutritional support, antibiotics for secondary infections, etc.
Courtney two years after surgery. Although the jaw is foreshortened, excess skin was shaped in surgery to help improve function and also extend the appearance of the lower jaw. Photo by Peg Banks.
Frequent examinations are needed to watch for recurrence or progression. Periodic monitoring to watch for evidence of spreading disease, such as feeling the lymph nodes, lymph node aspiration, and chest X-rays is also indicated.
The median survival time for dogs that have mandibular SCC treated with surgery alone varies from 19-43 months, with a 1-year survival of 88-100%, a 2-year survival of 79%, and a 3-year survival of 58%.
The median survival time for maxillary SCC that was treated with maxillectomy varies from 10-39 months.
The local recurrence rate after mandibulectomy or maxillectomy is less than 10%.
Tumor-associated inflammation and invasion of the lymphatic system are indicators of a poorer prognosis.
Overall survival times are lower with SCC of the tonsils. In one study, median survival time was only 243 days, with a 1-year survival rate of 40% and a 2-year survival rate of 20%. The longest survival times occurred when surgery and chemotherapy were used together.