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What are the causes, symptoms, breeds susceptible to, and treatments for malignant melanoma in dogs?


Malignant melanoma in dogs is a malignant tumor that develops on the skin, inside the mouth, or on the tips of the limbs. In dogs, it is especially common in the mouth, causing bad breath and bloody drooling. Here, we will explain the causes, symptoms and treatment of malignant melanoma.Malignant melanoma in dogs is the most common malignant tumor in the mouth of dogs. Melanoma occurs in dark areas where melanin cells produce melanin pigment, such as the lips, lining of the mouth, and cheek mucosa.
It is a highly malignant tumor that easily metastasizes to the lymph nodes and lungs.
Although the cause of the disease is not yet clearly understood, the metastasis rate varies depending on the site of origin, and it is known that the metastasis rate is high when the tumor occurs in the mouth or on the limb, while the metastasis rate is not so high when it occurs on the skin.


Malignant melanoma in dogs can cause the following symptoms. You should see a veterinarian right away if you see any of these in your pet.

  • Bad breath
  • Lumps in the mouth make it easier for bacteria to infect. Bacterial infections cause bad breath, so watch out for changes in their breath.
  • Bloody drooling and stained fur around the mouth
  • Malignant melanoma makes relatively soft lumps, and when the lumps get bigger, they may tear and ulcerate.
  • Loss of appetite
  • Protruding lumps or boils, which are painful, can cause loss of appetite.

How to diagnose

  • Visual Examination
  • Many canine malignant melanomas occur in the oral cavity and are difficult to distinguish from stomatitis, gingivitis, or periodontal disease. Therefore, lumps and inflammation in the mucous membranes of the mouth should be treated with the possibility of it being malignant melanoma.

  • Cytological examination
  • Cytological examination is performed to distinguish malignant melanoma from difficult-to-heal periodontal and skin diseases. In the cytodiagnosis test, a fine needle is inserted into the tumor, and a small amount of cells that enter the needle are observed under a microscope. The procedure is almost painless and can be performed without anesthesia.

  • CT scan
  • In the case of malignant melanoma occurring in the oral mucosa, a CT scan is performed to determine if the tumor has penetrated the jawbone or if it has spread to other parts of the body.

  • X-ray examination
  • For malignant melanoma in the limb area, an x-ray is performed to see if the bone has dissolved. X-rays may also be performed to check for metastasis.
  • Ultrasonography
  • Ultrasonography is used to check for metastasis in the abdominal cavity.

How to treat melanoma in dogs

  • Surgery
  • If the tumor is in the early stage, about 1 cm in diameter, a complete cure is possible by extensive removal of the lesion, including the normal tissue around it. If the tumor is located in the mouth, it is often necessary to remove the entire jawbone around the tumor.

  • Radiation therapy
  • After the tumor is surgically removed until it cannot be seen, radiation therapy is performed. Even if the tumor cannot be removed completely, the growth of cancer cells can be stopped by reducing the volume of the tumor and administering radiation therapy.

  • Anticancer drug therapy
  • If the tumor has already metastasized or if radiotherapy cannot be applied to the area that could not be removed by surgery, anticancer drug therapy may be administered.

Diseases mistaken for

There are not many diseases that are easy to get mistaken for, but some of the tumors and inflammations that can occur in the mouth are as follows.

  • Squamous cell carcinoma
  • Squamous cell carcinoma in dogs is a malignant tumor that can occur in the auricle, nose, base of the nails, lips, and gums. When it is found in the mouth, drooling and strong halitosis are the initial symptoms, but the tumor rarely metastasizes throughout the body.

  • Fibrosarcoma
  • Canine fibrosarcoma can develop in any part of the body, including the mouth, face, legs, mammary glands, and symptoms vary depending on the site. When it is found in the mouth, the tumor is less likely to spread to the lymph nodes or lungs, but it tends to grow relatively large in the mouth.

  • Periodontal Disease
  • Periodontal disease in dogs is a disease in which bacteria in dental plaque adhere to the tooth surface and cause inflammation of the periodontal tissues. It is said that about 80% of adult dogs and cats over the age of 3 have periodontal disease. The term “periodontal disease” is used to describe both gingivitis, which is inflammation of the gums, and periodontitis, inflammation that extends to other periodontal tissues.

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