What is squamous cell carcinoma in the mouth of a cat?

Squamous cell carcinoma (SCC) is the most common oral (mouth) tumor in cats and typically affects middle-aged to older cats. Factors that may increase the risk of oral SCC include flea collars, high volumes of canned food, and household smoke exposure; however, there is no one factor that is known to cause SCC. Unfortunately, oral SCC is an aggressive locally invasive tumor that is difficult to control. Oral SCC appears to have a low rate of spread to other sites (metastasis) but this may be simply due to the short survival times following diagnosis.

What are the signs and symptoms of oral squamous cell carcinoma?

Most cats are examined by their veterinarian following identification of an oral mass or swelling by the owner. Oral SCC in cats typically:

• Develop as large, invasive and often ulcerated tumors
• Occur anywhere in the mouth, including under the tongue, along the palate (roof of the mouth), the upper jaw (maxilla) or the lower jaw (mandible)
  
• Invade bone and therefore can be associated with significant discomfort and/or swelling along the jaw
  

Other symptoms can include:

• Halitosis (bad breath)
• Loose teeth
  
• Pain associated with the face or chewing
  
• Excessive drooling and often blood-tinged drool
  
• Inability to close or open the mouth completely
  
• Lack of grooming
  
• Decreased appetite and weight loss

How is a diagnosis of oral squamous cell carcinoma made?

Diagnosis of oral SCC requires a biopsy of the tumor often with the cat under general anesthesia so that a good sample of the tumor can be collected. A thorough oral examination can be performed at the same time, and the tumor is typically measured and documented along with the location. 

While not diagnostic for SCC, the diagnostic work-up includes:

• Blood work (complete blood count and serum chemistry profile among other possible tests)
• Lymph node assessment via cytology (needle sampling)
  
• Chest radiographs (X-rays) in order to confirm that the tumor SCC is confined to the mouth. 
  

For some tumors, particularly those located in the front of the upper jaw (maxilla) or lower jaw (mandible), advanced imaging with computed tomography (a CT scan) may be recommended.

What treatments are available for oral squamous cell carcinoma?

• If possible, surgery is the treatment of choice for small tumors, particularly those located in the front of the lower jaw. Most cats present with large (> 2 cm/1 inch) tumors that are difficult to remove completely with surgery. Radiation therapy after surgery may be recommended in some cases. 
• Palliative (short course) radiation therapy may be offered instead of surgery to provide comfort rather than attempt to cure the cancer. 
  
• Chemotherapy likely does not play a pivotal role in management but may help provide comfort or temporary control of the SCC in some cases. Unfortunately, if the mass cannot be removed, there is no known effective treatment for oral SCC in cats that offers long-term control and survival.
  
• An important focus for management of oral SCC needs to be placed on maintaining nutrition and comfort for the patient. 
  

Adjusting the consistency of the food (from kibble to canned stewed diets to canned soft or gruel diets) can help ensure whichever form is easiest for the pet to ingest is available. Non-steroidal anti-inflammatory drugs can be useful in managing discomfort. Furthermore, the use of pain relievers should be a focus of therapy to reduce discomfort for the patient. 

What is the prognosis for oral squamous cell carcinoma?

The prognosis for cats with oral SCC is poor and most cats will have survival times ranging from 3 to 6 months. Cats with small tumors located on the lower jaw (mandible) that are treated with surgery have a better chance of surviving for one year particularly if the mass can be completely removed. 

Edited by:
Christine Swanson, DVM, DACVIM (Oncology)
April, 2020