It can be concerning if you find a new growth or bump on your dog’s skin. There are many types of skin lesions seen in dogs, and while some are benign, others are cancerous. Just like in people, there are sometimes clues that a skin lesion may be more or less concerning. However the best way to determine what’s going on with your furry friend is to see a vet for some additional evaluation.
Signs and Symptoms of Skin Cancer in Dogs
Skin cancer usually presents as a growth or lesion on your dog’s body. It can take many different forms. It can be difficult to tell the difference between a benign and malignant lesion just by looking, which is why additional testing is usually indicated. However, certain types of skin cancers do tend to have a characteristic appearance, which is described below.
Types of Skin Cancer in Dogs
Skin lesions in dogs can be characterized as benign or malignant (cancerous). They are also classified based on location, size, physical appearance, and cell type of origin.
Benign skin lesions
Benign lesions are not invasive and do not spread to other parts of the body.
This is a benign lesion often occurring in younger dogs (less than three years of age). It is typically a raised, red, raspberry-like lesion. In many cases, no treatment is needed as it usually regresses on its own within two to three months; however, surgical removal may be indicated if it is bothering your dog.
While benign, histiocytomas can appear similar to mast cell tumors, so it is always a good idea to have your vet evaluate and monitor this type of mass.
Sebaceous gland tumors
These warty skin growths are common in older dogs.They may bleed, scab, or become infected, but are generally easy to remove. Again they can be difficult to distinguish from malignant skin lesions, but they can just be monitored if they are benign and not bothering you or your dog.
There are many other types of benign skin lesions, including infections, bug bites, and other types of cutaneous (skin) growths.
Cancerous skin lesions
Malignant skin lesions can spread locally to nearby bone and tissue, and other body parts. These types of lesions have the potential to affect your dog’s health and life expectancy. There are many different types, but three of the most common are described below.
Squamous cell carcinoma
These malignant tumors arise from the top (squamous) layer of the skin. They often occur in light-skinned areas, especially those that are exposed to the sun but can also affect the paws and nail beds (subungual). They may appear as raised, red, warty, or ulcerated patches or lumps. Treatment usually involves surgical removal. If the cancer is on a toenail, then amputation of the digit is required, as this form of cancer can be more aggressive. While there are breed and genetic factors at play, limiting sun exposure and using a pet-safe sunscreen, especially in white dogs, may help prevent this skin cancer.
This tumor occurs in melanocytes, the cells that produce melanin/pigment. There are both benign and malignant forms. They can occur anywhere on the body, and are often (but not always) pigmented, raised, ulcerated, lumps. Melanoma in the mouth and on the toes are common and concerning. Male dogs are at more risk of melanomas than females, and certain dog breeds also face an increased risk.Malignant melanomas grow quickly and can spread to other parts of the body. Treatment usually involves surgery with wide margins. Toe amputation or removal of part of the jaw may be needed depending on location. Follow-up with radiation or immunotherapy (melanoma vaccine) may also be needed to help prolong survival.
Mast cell tumor
Mast cells are a type of white blood cell that are involved in allergic reactions, during which they degranulate and release histamine. Tumors arising from these mast cells are the most common skin tumors in dogs, can occur anywhere on the body (as well as internally) and vary widely in their appearance (they are often known as the great pretender).
Mast cell tumors may take the form of a red, raised, swollen lump that may seem to shrink and grow in size. These tumors may also cause systemic signs due to degranulation. A pathologist will be able to “grade” the tumor when evaluating cells from a biopsy under the microscope, which will provide critical information about how aggressive the cancer is and how likely it is to spread. Staging to look for spread is also important. Treatment usually involves surgery with wide margins. Higher-grade tumors will also need follow-up treatment with chemotherapy and radiation, and have a poorer prognosis.
There are many other types of malignant skin lesions seen in dogs.
What Breeds Are at Risk?
Skin cancer can occur in any breed of dog. However certain breeds may be more at risk for certain types of skin cancer.
Squamous cell carcinomas
Dalmatians, Pit Bull Terriers, Bull Terriers, Beagles, and other light-skinned breeds are predisposed. Subungual lesions are more common in dark-haired breeds such as Giant and Standard Schnauzers, Gordon Setters, Briards, Kerry Blue Terriers, Scottish Terriers, and Standard Poodles.
Melanomas are prone toMiniature and Standard Schnauzers, Doberman Pinschers, Golden Retrievers, Irish Setters, and Vizslas. Malignant melanomas are often seen in Miniature and Standard Schnauzers and Scottish Terriers.
Mast cell tumors
Boxers, Pugs, Rhodesian Ridgebacks, and Boston Terriers are commonly affected breeds.
Diagnosing Dog Skin Cancers
There are two ways that your veterinarian may diagnose skin cancer.
Fine needle aspiration (cytology)
This involves using a needle and syringe to collect a small sample of cells from the mass to evaluate under the microscope. This is generally a quick and easy way to start, but it may not always provide a definitive diagnosis.
This involves surgically removing part of all of a mass and submitting it to a pathologist for histopathology to provide an accurate diagnosis. Depending on the size or location, this may need to be done under general anesthesia or sedation with a local block. If the entire mass is removed, this option may also be curative, as the pathologist will be able to confirm that all cancer cells have been removed. For small and less concerning masses, many vets may recommend doing a biopsy or mass removal at the same time as a dental cleaning under anesthesia.
If your veterinarian is concerned about the spread of cancer to other parts of the body they will recommend chest radiographs, an abdominal ultrasound, or other tests. This is known as staging. Staging is important because it can give vets and pet parents important information about if and where cancer has spread, and helps guide treatment recommendations.
So which types of skin lesions should be tested? Any new lesions on your dog. Even more concerning types of cancer can often be successfully removed if caught early when they are small in size.
How is Dog Skin Cancer Treated?
Treatment will vary depending on the type of skin lesion, its size and location, and your pet's overall health. Surgical removal is generally recommended if the mass is suspected to be malignant, or if it is bothering your dog (bleeding and scabbing, hindering their activity level, etc.) or you (masses may also be removed for aesthetic reasons). There are several reasons why surgery may not be recommended for your pet, including poor overall health, concurrent disease processes, and the size and location of the mass.
If the mass is unable to be removed or if the cancer has already spread, referral to an oncologist for chemotherapy and/or radiation may be an option.
Can Dogs Recover From Skin Cancer?
Again this depends on the type of cancer and available treatment options. In many cases, surgical removal is curative, and your dog can go on to live a normal life. However, in some cases, the prognosis is less favorable, especially if the cancer has spread. In some cases, your dog may be predisposed to developing additional cancerous lesions in the future as well. Your vet or oncologist will be able to help provide more information about your individual furry family member and what to expect. While any type of cancer is scary, many excellent treatment options are available, with even more being developed.