“The cause of most skin cancers in dogs is unknown,” writes CanineCancer.com. “Exposure to the sun has been shown to cause a higher incidence of three types of skin cancer: squamous cell carcinoma, basal cell carcinoma and hemangioma. There may be a genetic basis for the development of certain cancers as certain breeds of dogs have been found to have a higher incidence of skin cancer.”
Sadly, skin cancers are the most common tumors in dogs, accounting for roughly one-third of all tumors. There are many types of skin cancer, but mast cell tumors (MCTs or mastocytomas) occur most often.
Skin cancers may appear on or near the surface of the skin (these are called superficial) or under the skin (subcutaneous) as masses. It is extremely important to learn the difference between benign lesions and malignant masses. CanineCancer.com states that 20 to 30 percent of skin cancers found in dogs are malignant.
“Some dermal masses with malignant potential are mistaken for benign lesions, therefore it is important to have all skin masses evaluated by a veterinarian quickly after they are detected,” CanineCancer.com notes.
Skin cancer, like most cancers, occurs more frequently in middle-aged to senior dogs, although some skin cancers can occur in younger dogs.
What Types of Skin Cancers Can Dogs Get?
There are several different types of skin cancers dogs can get, but the following three are the most common, according to pets.webMD.com:
This type of skin cancer affects pigmented cells known as melanocytes. Dogs often develop benign tumors in pigmented cells that do not metastasize (spread to other organs), which are called melanocytomas. These are often found on the hairy areas of the dog’s body, but they can also be found on the mouth or mucous membranes.
This type of skin cancer grows quickly and will spread to other organs like the liver and lungs.
There is no known cause, but genetics seem to play a significant role in its development. Trauma to or compulsively licking a particular spot on the skin may trigger the cells to multiply and mutate during the division process and become cancerous.
Squamous Cell Carcinoma
This type of skin cancer is often caused by sun exposure, although scientists think there may be a connection between the papilloma virus and squamous cell tumors in certain breeds.
Squamous cell carcinoma occurs in the epidermis. These cancerous cells will not spread to surrounding lymph nodes, but it is an aggressive cancer nonetheless and may destroy much of the skin tissue surrounding the tumor.
Mast Cell Tumors
The most common of the three, this cancer develops in the mast cells of the immune system. Unfortunately, veterinarians are at a loss as to what causes mast cell tumors to develop, although there have been cases where it has been linked to inflammation or irritants on the skin. Scientific evidence suggests genetics could factor in as a cause as well as the hormones estrogen and progesterone.
What Are the Symptoms of Skin Cancer in Dogs?
Just like in humans, skin cancer often presents itself as a lump. The skin may be red and/or flaky and itchy, which could cause your dog to lick, bite or scratch at the infected area.
CanineCancer.com writes, “Systemic symptoms depend on the location and type of tumor, how aggressive it is and whether it has metastasized [spread].”
These symptoms include:
- Loss of appetite
- Vomiting (it may be bloody)
- Wounds that do not heal
- Enlarged lymph nodes
- Abdominal pain
- Dark or black feces
- Irregular heart rhythm and blood pressure
- Labored breathing
- Various bleeding disorders
Also just like in people, early detection is key to fighting your dog’s skin cancer. It is crucial to give your dog a thorough exam at least once a month that includes looking in his mouth and under his tail.
If he is presenting any of the following symptoms, get him to the vet immediately.
- Any lumps or bumps
- Scaly or crusty lesions
- Areas of skin that have changed color
- Lesions or tumors that do seem to heal or bleed easily
- Swelling in the breast tissue
- Discharge from a nipple
How is Skin Cancer Treated?
Treatment depends on the type of tumor and how advanced the disease is when your dog is diagnosed.According to CanineCancer.com, the options include:
- Surgery: Only if the tumor has not spread and can be removed entirely without compromising the associated tissues. Your vet may recommend radiation prior to the surgery to reduce the size of the tumor so that the surgery is more successful at fully removing the tumor.
- Radiation: As mentioned, this is used to reduce the size of the tumor if it cannot be successfully removed with surgery.
- Chemotherapy: This is used for cancers that have spread to other tissues.
- Cryosurgery: This procedure involves freezing the tumor and surrounding skin for removal. It is used only with small tumors.
- Photodynamic therapy: This new treatment employs the use of a dye, which is injected into the bloodstream, localizing the cancer cells. A laser is then used to excite the cells and cause them to die.
In June 2009, the U.S. Food and Drug Administration (FDA) approved the drug Palladia. It is used to treat skin-based mast cell tumors, which are responsible for one in five cases of canine skin cancer.
What is the Prognosis for Skin Cancer?
The prognosis depends on the type of cancer, where it’s located and how advanced the disease is.
“Surgery is often the first step for malignant melanomas,” according to pets.webMD.com. “If the melanoma cannot be removed in its entirety, or if it has spread to nearby lymph nodes, radiation is commonly used. In these situations, the cancer may go into remission nearly 70 percent of the time, though recurrence is common. Chemotherapy is often used in combination with surgery and/or radiation therapy. There is also a vaccine that causes the dog’s own immune system to attack tumor cells, which often successfully extends the survival time of dogs with oral melanoma.”
Fortunately, squamous cell carcinomas can often be removed surgically without the need for radiation or chemotherapy. If the tumors are in inoperable locations, photodynamic therapy and the drug piroxicam may be beneficial in treating the cancer.
The best treatment for mast cell tumors is surgery, with or without radiation therapy, depending on the size and location of the skin cancer. Taking into account the grade and the degree to which the cancer has spread, chemotherapy and/or steroids may be used.
If the cancer is too advanced, or there are other health complications, the only option is to make the dog as comfortable as possible.
Find A Vet HOW TO articles are intended for informational purposes only. You should always consult with your veterinarian about any health issues affecting your dog.