A Pet Parent’s Guide to Melanoma

When we think of melanoma, we often think of skin cancer from sun exposure. In our pets, however, melanoma behaves very differently. It most often appears in the mouth, where it is a serious and aggressive cancer. Understanding the signs of melanoma, especially oral melanoma, is critical for early detection. At Harmony Pet Clinic, we want to give you the information you need to spot the signs and know when to seek help.

What is Melanoma?

Melanoma is a cancer of the melanocytes, which are the cells that produce pigment (melanin). This is why the tumors are often dark brown or black, though some can surprisingly lack pigment (these are called amelanotic melanomas). While melanoma can occur on the skin, the most common and dangerous forms in pets appear in the mouth, in the nailbeds, and sometimes in the eye.

Oral Melanoma in Dogs: The Most Common Form

Oral melanoma is the most frequently diagnosed oral cancer in dogs. It is highly aggressive, meaning it grows quickly and has a strong tendency to spread (metastasize) to the lymph nodes and lungs. Breeds with dark-pigmented gums and mouths, like Scottish Terriers, Schnauzers, and Poodles, are more at risk.

Signs of Oral Melanoma

Because these tumors grow inside the mouth, they can be easy to miss. That’s why regular at-home mouth checks are so important.

• A New Mass or Lump: Look for any new growth on the gums, lips, palate (roof of the mouth), or tongue.
• Bad Breath (Halitosis): A sudden worsening of breath odor is a major red flag.
• Difficulty Eating: You may notice your dog dropping food, chewing on one side of their mouth, or being reluctant to eat hard kibble.
• Drooling: Especially if it’s new, excessive, or tinged with blood.
• Facial Swelling: Swelling on one side of the face can indicate a large underlying tumor.

Treatment for Malignant Melanoma

Because malignant melanoma is so aggressive, treatment needs to be too. The goal is to control the local tumor and fight the systemic spread.

• Surgery: The first step is aggressive surgical removal of the tumor. For oral melanoma, this can sometimes involve removing a portion of the jawbone to get clean margins.
• Radiation Therapy: This is often used after surgery to kill any remaining cancer cells in the area.
• The Melanoma Vaccine: This is a groundbreaking form of immunotherapy. It’s not a preventative vaccine, but a therapeutic one that stimulates the dog’s own immune system to recognize and attack melanoma cells throughout the body. It has dramatically improved survival times for many dogs.

Melanoma in Cats

Melanoma is much less common in cats. When it does occur, it is most often found in the eye (ocular melanoma) or on the skin. While skin melanoma in cats can be benign, ocular melanoma is often malignant and may require removal of the eye (enucleation) to prevent its spread.