Malignant Melanoma in Dogs

Malignant melanoma is often fatal within one year even with treatment to remove the cancer. The average survival time for this disease is up to about 10 months, though dogs can live up to 36 months with immediate surgical removal of the melanoma. The only treatment is surgery because chemotherapy and radiation are not effective. There are four stages of malignant melanoma and each has its own survival time.

• Stage one (smaller than 2 cm): about twelve months
• Stage two (2-4 cm): about eight months
• Stage three (larger than 4 cm or tumor that has spread): about four months
• Stage four (extensive metastasis): about one month

Malignant melanomas in dogs are cancerous lesions or tumors on the skin, mouth, or toenails. These are more common in older male dogs and certain breeds such as Schnauzers and Terriers. The most often seen melanoma is a raised and ulcerated nodule that is darker than the surrounding skin, although some melanomas are amelanotic (not pigmented). Malignant melanomas are an aggressive type of cancer that frequently spread into other areas of the body.

The signs that your dog may have malignant melanoma can vary depending on where the cancer originates. The three most common places are the mouth (oral), skin, or toes.

Oral

• Dark (black, brown, grey) lump or lesion on mouth, tongue, lips, or gums
• Facial swelling
• Bloody drool
• Foul breath
• Unable to eat
• Loose teeth
• Dropping food from the mouth

Skin

• Rash or grouping of small blister-like lesions, usually on the feet, underbelly, and face
• Large lump anywhere on the body, usually darker than the skin surrounding it
• Pain or bleeding from a spot or lesion of unknown origin that does not seem to be healing

Toes

• Swelling of the foot
• Discolored toenail
• Malformed toes
• Loose toenail

Types

There are three main types of malignant melanoma.

• Oral malignant melanoma occurs in the mouth, gums, lips, and jaw
• Dermal malignant melanoma can be found anywhere on the skin but most often on the abdomen or face
• Malignant melanoma of the toes includes the foot, bones, and digits

The cause of malignant melanoma in dogs is unknown. In humans, one of the main causes of this disease is sun exposure, but this does not seem to be the case with dogs, who are protected by their fur and thick skin. There are some risk factors though, which are:

• Older dogs
• Males
• Certain breeds (Schnauzer, Doberman Pinscher, Springer Spaniel, Cocker Spaniel, Airedale, Boston Terrier, and Scottish Terrier)

Diagnosis is pretty easy if you are able to get a veterinary oncologist or one who specializes in skin diseases. Most veterinarians can do a physical examination and may suspect the diagnosis right away, but will not confirm it until blood tests and a biopsy are done. During the examination, be sure to tell the veterinarian as much as you know about the issue and if you have given your dog any medication; prescription or otherwise. The examination includes a complete skin and haircoat analysis, reflexes, body temperature, weight, blood pressure, heart rate, respirations, breath sounds, pupil reaction time, and oxygen level.

Laboratory testing includes a complete blood count (CBC), serum analysis, platelet count, glucose level, blood urea nitrogen (BUN), liver panel, packed cell volume (PCV), and a urinalysis. A fine needle aspirate will be gathered for microscopic analysis. A biopsy may then be taken, depending on results.

Chest films (x-rays), lymph node aspiration, and possibly a CT scan with contrast dye will all be used to stage the disease. There are four stages, as mentioned earlier.

While treatment of malignant melanoma depends on the progression of the disease, surgery, radiation, and chemotherapy are strongly suggested. However, none of the treatments are an actual cure as the melanoma grows back in most cases.

Surgery

As long as the cancer has not spread too far, surgical removal of the melanoma is always the first part of the treatment plan. This is usually a simple surgery, depending on the location, and only has slight risks (usually less than not having the surgery). The veterinarian removes the melanoma and a large area of tissue around it to improve the chance of survival.

Radiation

This treatment is done only in cases where there is still a risk of tumor regrowth. However, it has not shown to add much time to the prognosis of survival.

Chemotherapy

Although some veterinarians still use chemotherapy, this is not usually very effective.

Supplemental Care

Keeping your dog as pain free as possible and increasing quality of life are the veterinarian’s goals. This includes providing pain killers, intravenous (IV) fluids, oxygen therapy, and maybe a feeding tube as needed. The veterinarian will describe what is being done at each step, but ask questions if you are unsure.

The prognosis for most dogs who have malignant melanoma is not good. Usually, by the time the symptoms are noticed, the cancer has spread. Be sure to follow all the directions that the veterinary team has given you in order to give your dog a good quality of life in the meantime, and call the veterinarian if you have any concerns.