Melanoma is a well known and feared cancer in humans and there are several steps we take to prevent this skin cancer.
But did you know that our four-legged friends are also subject to developing melanoma? The melanoma in the dog accounts for up to 7% of malignancies diagnosed in canine friends. And it’s not just about the skin.
What is melanoma in dogs?
Melanoma in dogs is a cancerous tumor, which usually appears as a pigmented mass. In dogs, it can be found in the skin, eyes or mouth. The prognosis varies depending on the location, and treatment involves surgery possibly combined with radiation or chemotherapy.
What does melanoma in dogs look like?
A canine melanoma looks like a lumpy, firm and usually black. However, some canine melanomas are non-pigmented; this is especially true for some cancers that develop in the mouth.
The size of the melanoma varies from a few millimeters to several centimeters according to the evolution. Its surface can be smooth or bumpy.
In dogs, melanomas are distinguished by:
- Skin (located on the body, head or limbs)
- Dita
- Oral cavity and lips
- Eyes
What causes melanoma in dogs?
Melanomas are cancerous tumors that develop from certain cells: i melanocytes, the cells responsible for skin pigmentation. Canine melanoma accounts for 4 to 6% of skin cancers in dogs.
In humans, melanomas develop from moles called “nevi.” The influence of sun exposure on the development of this serious cancer is well known. In dogs nevi are rare and UV less dangerous due to the density of the hairs that protect the animals. Additionally, many canine melanomas develop in the mouth.
Canine and human melanomas have many similarities; moreover, melanoma in dogs is one of the best models for studying non-UV-dependent forms of metastatic melanoma in humans.
It is believed that dogs with dark coats would be predisposed. Likewise, there are several breeds at risk. Among them: the Rottweiler, the Golden Retriever, the Chihuahua or the Airedale terrier or the Chow Chow.
Symptoms of dog melanoma
Symptoms of melanoma in dogs vary by location of the tumor. The clinical signs, therefore, can range from asymptomatic forms to those characterized by tooth loss, subcutaneous swelling, drooling, swollen eyelids, hyperlacrimation, epistaxis, and so on.
Pictures of melanoma in dogs
Below are some photos of melanomas in dogs located in different parts of the body such as the mouth, skin and eyes.
Melanoma in the dog’s mouth
Or:
Melanoma in the dog eye
Cutaneous melanoma in dogs (belly, head, paws)
How serious is canine melanoma?
First of all, any black bump discovered on a dog’s body or in the mouth isn’t necessarily melanoma. Some pigmented skin cancers are just melanocytomas, benign tumors (similar to moles in humans). Conversely, some oral melanomas are not black.
The diagnosis of melanoma in dogs is made by the veterinarian on the basis of the clinical examination and histological examination (examination of the cells under a microscope) on a needle puncture, a biopsy (removal of a small fragment of tumor) or after removal of the whole mass.
At this stage of the diagnosis, an extension assessment is done to find out if the melanoma has already started to spread. Invasion in the lymph nodes and metastases in the lungs are looked for by X-ray or CT scan.
The prognosis is very variable depending on the location of the neoplasm. Cancers of the oral cavity and fingers are usually more aggressive:
- It is believed that i mouth melanomas of the dog have the worst prognosis. They have strong local aggression (deep tissue invasion) and metastasize rapidly. Median survival after surgery is less than 2 years.
- Also finger melanomas have significant metastatic potential: pulmonary nodules are present in over 30% of cases at the time of diagnosis.
Canine benign melanoma
Benign melanomas in dogs usually present with small, pigmented, nodular skin formations that do not adhere to the deep layers of the epidermis.
Canine melanoma treatment
The first axis of treatment is the surgery: must be early and include all the invaded tissues. This involves amputation of a finger in case of digital melanoma or a mandibulectomy (removal of bone from the jaw) in case of oral melanoma.
In some cases of advanced or poorly positioned tumors, complete excision may prove difficult or even impossible.
The size of the tumor is an important prognostic factor: a mass (pigmented or not) should not be ignored, especially if it develops in the mouth, on the lips or on a finger. Non-metastatic cutaneous melanomas and digital melanomas can be treated with surgery.
Tumor excision can be completed in a veterinary cancer center with radiation and chemotherapy. These adjuvant strategies are disappointing in the treatment of canine oral melanoma.
Immunotherapy for melanoma in dogs
Immunotherapy, still in the research phase, could prove to be interesting in the treatment of canine melanoma, often fatal for our beloved pets.
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Article written for Todocat.com and:
Isabelle Vixege
Veterinary doctor