The most common tumors of the salivary gland in both dogs and cats include adenocarcinomas and carcinomas (squamous cell carcinoma, mucoepidermoid carcinoma, anaplastic carcinoma and complex carcinoma). 

Surgical removal of the tumor is recommended, but may be difficult because of the invasiveness of the tumor in this location. The anatomy of the salivary gland in this location is complex due to the many nerves and extensive blood vessels.

The reported median survival time for dogs is around 550 days and in cats 516 days.

What is it? 

• A tumor of the salivary gland is an abnormal growth of the salivary gland which can spread to other parts of the body.
• The most common tumors of the salivary gland in both dogs and cats include adenocarcinomas and carcinomas (squamous cell carcinoma, mucoepidermoid carcinoma, anaplastic carcinoma and complex carcinoma). 
• 75%-80% of all salivary gland tumors are located in either the parotid or mandibular salivary glands.  In dogs the mandibular gland is the most commonly affected and the parotid gland is most commonly affected in cats. 
• Tumors of the salivary gland are uncommon in cats and dogs.
  

Anatomy

• Dogs and cats have four major pairs of salivary glands, which include the parotid, mandibular, sublingual and zygomatic glands.  There are many nerves and blood vessels connected with these glands.
• The parotid gland is located over the ear canal and the mandibular gland is located just behind the jaw bone.   The mandibular gland is easier to remove and thus complete removal is likely.  The parotid gland is difficult to remove. 

Clinical signs

• Signalment
  • Breeds
    • Cats are more commonly affected than dogs. 
    • Over represented breeds include
      • Siamese cats or Siamese crosses
      • Spaniel breeds
      • Poodles
  • Age:  Affecting older animals with the mean age about 10-12 years old. 
  • Sex: males and females are equally affected.
• Signs
  • A non-painful firm mass in the location of a salivary gland may be the only sign.
  • Difficulty breathing
  • Difficulty swallowing
  • Stale or foul smelling breath
  • Protrusion of the eye
  • Swollen lymph nodes
  • Weight loss
  • Anorexia (not eating)

Diagnosis

• A diagnosis of salivary gland tumors is based on physical exam findings and tissue biopsies of the salivary gland and regional lymph nodes. 
• Diagnostic imaging such as skull and chest radiographs (x-rays), CT scan or MRI are used to determine if there is spread of the tumor (staging), which can be found in both regional lymph nodes and the lungs. 
• Staging of the disease will likely determine survival time in dogs but not in cats.  

Treatment

• Complete surgical removal of the tumor is recommended, but may be difficult because of the invasiveness of the tumor in this location. The anatomy of the salivary gland in this location is complex due to the gland's association with many nerves and extensive blood vessels. Surgery may be curative.  Both dogs and cats will have increased survival times with surgery alone (if there is complete resection) or with surgery and radiation. 
• Radiation therapy or chemotherapy is recommended if the tumor cannot be completely removed or when there is spread of the tumor.

Potential complications 

• Removal of the parotid gland may result in damage to the facial nerve, which can result in the inability of your pet to blink an eye, drooling, or drooping of the face on the affected side. 
  
• Removal of the mandibular gland may result in damage to the nerves of the tongue which can result in decreased function of the tongue. This is a very uncommon complication.
  
• With any anesthesia there are potential risks of an anesthetic reaction.  This is an uncommon complication under the care of our trained specialists. 
  
• A pocket of fluid may accumulate beneath the incision site. This complication is usually minimized by having a drain in place.
• Infection could develop, but is uncommon.
  
• Side effects of pain relieving medications or antibiotics, can include vomiting, diarrhea, and loss of appetite.  If any of these signs occur notify your pet's surgeon.

Aftercare

• Rest: Your pet’s activity needs to be restricted to short leash walks and no off leash activities for at least two weeks to allow for healing.
  
• The incision should be checked daily for signs of infection.
  
• If a drain is placed daily bandage changes may be required. 
  
• Care of the drain. This may include removal of fluid from the drain bulb and keeping the site of the drain clean. 
  
• Medications that you may need to administer to your pet may include:
  
  • Antibiotics: may be prescribed to prevent infection.
  • Analgesics (pain relieving medication): will be prescribed to minimize pain after surgery.

Prognosis

• The reported median survival time for dogs is around 550 days and in cats 516 days.
• Cats are usually diagnosed when the disease is more advanced; in such cases the tumor has spread to lymph nodes and or the lungs.