Mouth Cancer (Melanocytic) in Dogs

Oral Melanocytic Tumors in Dogs

Melanocytic tumors of the oral cavity arise from a local invasion of neoplastic melanocytic cells, or melanin-producing cells found in multiple sites throughout the body, including the mouth and skin. These tumors arise from the gingival surface and are aggressive in nature. They are usually raised, irregular, ulcerated, have a dead surface, and are highly invasive to bone.

Melanocytic tumors are the most common oral malignant tumors in dogs, commonly affecting dogs over 10 years of age. Such tumors may cause death as these render animals unable to eat, lose weight, and metastasis to other body parts.

Symptoms and Types

• Loose teeth
• Bad breath (halitosis)
• Excessive salivation (ptyalism)
• Difficulty swallowing (dysphagia)
• Oral discharge containing blood
• Weight loss (cachexia)

Causes

The underlying cause for oral melanocytic tumors is currently unknown.

Diagnosis

You will need to give a thorough history of your dog’s health, including the onset and nature of the symptoms, to your veterinarian. He or she will then perform various laboratory tests, including a biochemistry profile, urinalysis, and complete blood count -- the results of which are typically normal -- as well as a physical examination, especially of the oral cavity.

Your veterinarian will also take a small deep tissue sample from the mass in the oral cavity, including a part of bone to be sent to a veterinary pathologist for further evaluation. Such biopsy samples are usually helpful in making a definitive diagnosis. In addition, X-rays of the oral cavity, skull, and lungs will help in the evaluation of the extent and location of metastasis.

Treatment

After reaching a definitive diagnosis and careful evaluation, your dog’s veterinarian, in consultation with a veterinarian oncologist, will plan surgery to excise the tumor mass along with part of the bone involved. Your veterinary oncologist will also suggest chemotherapy in combination with radiation therapy to further enhance the treatment's effectiveness. Soft foods are recommended after surgery to prevent tumor ulceration and to ease out ingestion of food.

Living and Management

Prognosis depends upon the stage, location, extent of metastasis, and extent of the tumor mass removed during surgery. Unfortunately, the overall prognosis in most dogs is not good and most die due to rapid loss of body weight, an inability to swallow correctly, and the spread of the tumor (to the lymph nodes in 80 percent of the cases). Treatment, therefore, is directed toward improving the animal's quality of life.

After surgery, you should expect your dog to feel sore. Your veterinarian will give you pain medication to help minimize your dog’s discomfort, which should be used with caution (one of the most preventable accidents with pets is overdose of medication). Follow all your veterinarian's directions carefully and limit your dog's activity while it heals, setting aside a quiet place for it to rest away from household activity, children, and other pets.

It is important to monitor your dog's food and water intake while it is recovering. Due to involvement of the oral cavity, these patients are not able to take feed for number of days. Your veterinarian will devise a diet plan, which will include highly palatable and nutritious foods. As affected dogs already have a tendency to lose weight, providing food to keep body weight within normal range is of utmost importance. 

In addition, chemotherapy medications have the possible toxic side effects, so your veterinarian will need to closely monitor your dog's stability, changing dosage as necessary. He or she will also conduct routine X-rays of the skull and lungs, and ask you to bring the dog in for regular evaluation visits to check progress and for recurrence.