Melanoma is a rather common form of canine cancer that usually occurs on the skin or in the mouth. Symptoms depend on the location of the cancer. Read on and find out more about the possible causes and risk factors, diagnosis and treatment of this cancer. In particular, there is now a new vaccine called the Canine Melanoma Vaccine DNA that can be used as one treatment option.
Melanomas are tumors arising from melanocytes - skin cells of the basal skin layer that produce pigment and color of the skin. Melanoma in dogs in a common form of skin cancer. These tumors can originate from various parts of the dog's body, but mostly the mouth, the skin, and the toes.
Melanoma tumors in dogs often arise as solid fleshy lumps and are usually dark in color (pigmented), although once in a while unpigmented melanomas can arise.
Not all melanoma tumors are cancerous. Melanoma tumors that occur on the skin are mostly (about 85%) benign. However, canine melanomas tend to be malignant when found in the mouth, on the toes and under the eyes. They can also spread to other organs quite fast. Common sites of metastasis include the lungs, liver, the lymph nodes, and adrenal glands.
For melanomas that occur on the skin, they are single growths that may or may not be pigmented or dark in color. Generally speaking, benign melanomas are deeply pigmented, smaller, and well defined.
For dogs that have melanomas in the mouth, they usually show some of the following signs:
When the cancer grows and metastasizes to the lungs, the dog patient will start coughing (you may see blood being coughed up) and showing respiratory problems such as breathing difficulty. At the same time, the melanoma tumor itself enlarges and may become ulcerated, causing secondary infection to occur.
(A visitor to our Cancer Forum wrote how aggressive and terrible canine melanoma was. You can read about her dog's fight against melanoma here.)
Please also read other visitors' experience:
The exact causes are not known. Unlike in people, dogs do not normally get skin cancer as a result of over-exposure to the sun.
Some veterinarians suspect that injuries to the skin or constant stress and trauma to the skin as a result of excessive scratching or licking can cause skin cells to divide and multiply frequently. During cell division, there may be sudden changes in genetic structures causing cancerous cells to form.
Canine melanoma is more common among middle-aged to older dogs (9 years or older). Also male dogs tend to be more commonly affected.
It seems that the following breeds tend to be affected by melanomas of the skin and toes:
The following breeds tend to be affected by melanomas in the mouth:
Common diagnostic tests for canine melanoma include:
For melanomas that occur on the skin, the treatment of choice is surgery.
However, melanomas that are found in the mouth are more difficult to deal with. Due to metastasis, these tumors are most often fatal unless prompt treatment is given to keep the cancer from spreading. Injection of chemotherapy into the tumor in addition to radiation can be used. Systemic chemotherapy can usually delay the growth of the tumor and can also relieve some of the symptoms caused by the cancer.
There is now a new vaccine called the Canine Melanoma Vaccine DNA that is being developed and tested. The vaccine works by injecting a protein into the body, alerting the immune system to the presence of the melanoma tumor protein. This product has been granted a license for testing in animals with stage II and III melanomas. (Update: Merial has now received full licensure for the vaccine.)
See the video below: