The skin is the most common site for cancer in the dog.  Among the types of skin cancer in dogs, melanomas are the most dangerous to life.

Melanoma Characteristics

Cells that produce pigment in the skin and hair are called melanocytes.  When melanocytes become cancerous, they are called melanomas.  Melanomas occur in the skin, mouth, or eyes.  They are the most common mouth tumors in dogs.  Those in the mouth or those involving the front feet are usually very aggressive, while those in the eye or on the body are usually not.   Melanomas will infiltrate surrounding structures and spread to other sites in the body through the bloodstream and lymphatic channels.  Scottish terriers, Airedales, Doberman pinschers, cocker spaniels, Irish setters, and schnauzers are predisposed to developing melanomas in later life (average affected age is 9 years).

Signs

Melanomas of the skin appear as solitary, dome-shaped, firm, brown to black, hairless growths rising above the surface of the surrounding skin.   Melanomas of the mouth can cause difficulty in swallowing, bad breath, bleeding from the mouth, loss of teeth, or facial swelling.

Diagnosis

The diagnosis is established by your veterinarian after microscopically examining cells aspirated (sucked) from the tumor or by biopsy after excising the tumor.

Treatment

The best treatment is wide surgical excision.  However, because of the rapid growth of the tumor and infiltration of surrounding structures, complete excision is often difficult to impossible.  Chemotherapy or radiation is usually unsuccessful.  With conventional treatments, approximately 25% of dogs with oral melanoma live one year after diagnosis.

            A new melanoma vaccine (Canine Melanoma Vaccine, DNA® - Merial, Ltd.) has recently been released which has more than doubled survival times in dogs with oral melanomas.  It has none of the adverse effects common with chemotherapy.  Tumor excision is advised before using the vaccine.  Under its current license for use, the vaccine must be administered by a veterinary oncologist using a special needle-free syringe for injection.  Four doses, once every two weeks are required with boosters every 6 months.

For more information, contact your local veterinarian or the MU Veterinary Medical Teaching Hospital 573-882-7821 or visit http://www.vmth.missouri.edu