5 Most Common Types of Skin Cancer in Dogs

Medically reviewed by Dr. Sara Ochoa

It makes sense to assume that the ultraviolet rays of the sun are what cause skin cancer in dogs. However, there are usually other contributing factors. 

In fact, the number one cause of skin cancer in dogs has nothing to do with the sun and everything to do with genetics.

Keep reading to discover the five most common types of skin cancer in dogs. We’ll cover the signs, diagnosis, and potential treatment options that may help prolong your dog’s life.

Early detection and treatment can make a big difference in your furry friend’s prognosis.

What Pet Parents Should Know About Skin Cancer in Dogs

One of the best ways to detect changes in your dog’s skin is to be aware of any new lumps, bumps, or skin discoloration.

You don’t have to memorize what every type of skin cancer looks like. You should, however, monitor your dog regularly for any skin changes.

The best time to do this is while grooming your dog. Bath time is an excellent opportunity to scan your dog’s skin for any signs of discoloration or unusual skin growths.

Between 60 to 80 percent of skin tumors in dogs are benign, meaning if you notice a lump on your dog’s skin, there’s a good chance it won’t be anything to worry about. However, the visible appearance of a growth can’t be used to predict whether or not it’s cancerous. Therefore, any new lump or bump you detect on your dog’s skin should be evaluated by a veterinarian.

“Medical Oncology: 5 Types of Skin Cancer in Dogs.” Veterinary Hospital, hospital.cvm.ncsu.edu/services/small-animals/cancer-oncology/oncology/5-types-of-skin-cancer-in-dogs. Accessed 5 June 2023.

Early detection of skin cancer in dogs is crucial.

When skin cancer is detected at an early stage, there are usually more treatment options available. The cancer may be limited to a small area and not have spread to other parts of the body.

When caught early enough, there are more treatment options available for your pet. These include surgical removal of the tumor, freezing the tumor (cryosurgery), or localized radiation therapy.

Early detection means that the tumor is likely smaller and, hopefully, has not had a chance to infiltrate deep layers of the skin or invade surrounding tissues.

Preventing Skin Cancer in Dogs

There are a few things pet parents can do to minimize the risk of skin cancer in dogs. This is especially important for dogs with thin fur or lighter coats.

Limit Sun Exposure

Dogs with thin fur or lighter coats may be more at risk of skin cancer, so limit their exposure to the sun. Avoiding the midday sun is a good idea for everyone involved. It’s usually the hottest time of day, when UV rays are at their peak.

Spay or Neuter Your Dog

Another important thing to do (for many reasons) is to have your dog spayed or neutered. The reason is that some types of skin cancer, like mast cell tumors, can be hormone dependent.

Mast cell tumors account for roughly 20% of all skin tumors in dogs. They are the most commonly diagnosed type of tumor in dogs.

By having your dog spayed or neutered, you reduce the risk.

Apply Pet Safe Sunscreen

The best way to protect vulnerable dogs from skin cancer is to limit their sun exposure.

If your dog is going to be outside for a while, provide shade for them and apply dog-safe sunscreen to vulnerable areas.

Regularly Examine Your Dog’s Skin

If you notice any unusual growths, sores that don’t heal, or changes in existing moles or skin pigmentation, have your dog seen by a veterinarian.

Remember, while skin cancer can be a serious concern for dogs, prompt detection, veterinary care, and appropriate preventive measures can greatly improve your pet’s prognosis and quality of life.

5 Most Common Causes of Skin Cancer in Dogs

The main causes of skin cancer in dogs include:

Hormonal Abnormalities

Certain hormonal conditions can contribute to an increased risk of skin problems. The risk of skin cancer may increase in dogs with secondary skin infections or chronic inflammation.

Cushing’s disease and hypothyroidism are a couple of examples of hormone-related disorders.

Genetics

Genetic factors are the number one cause of skin cancer in susceptible dogs. However, having a predisposition to skin cancer doesn’t necessarily mean your dog will get it.

Some breeds with a higher susceptibility to skin cancer include the following:

• Boxers
• Bull terriers
• Dalmatians
• Weimaraners
• Scottish terriers
• Golden retrievers

Sun Exposure

Dog breeds like the ones listed above have a higher risk of developing skin cancer. The reason for this is because those breeds either have light-colored or thin fur. This allows UV rays to penetrate the skin more easily.

Chemicals in the Environment

Prolonged exposure to certain environmental chemicals, including polycyclic aromatic hydrocarbons (PAHs), has been linked to an increased risk of skin cancer in both humans and animals.

These chemicals are created from the incomplete burning of organic materials. These include things like coal, oil, gas, wood, and tobacco.

According to the Illinois Department of Public Health, “long-term exposure to low levels of some PAHs has caused cancer in laboratory animals.”

Other chemicals that may be linked to various types of cancer, including skin cancer, include:

• Arsenic
• Pesticides
• Household cleaning products

Certain Viruses

Viruses have been associated with certain types of skin cancer in dogs. The canine papillomavirus (CPV) is one example. CVP is the virus that causes warts in dogs. While they’re usually benign, they can occasionally progress to squamous cell carcinoma (SCC).

Signs of Skin Cancer in Dogs

Being aware of the signs of skin cancer in dogs can be valuable for dog parents in detecting potential issues early on.

Some signs to watch for include:

• the presence of new or rapidly growing lumps or bumps on the skin, particularly those that don’t seem to heal or that show signs of ulceration.
• Unusual sores, wounds, or scabs that fail to resolve should also be monitored.
• Changes in the color, shape, or size of existing moles or skin tags can be indicative of skin cancer.

​Common Types of Skin Cancer in Dogs

In dogs, the most common types of skin cancer are mast cell tumors, melanomas, and squamous cell carcinomas.

Mast cell tumors make up 20% of all skin tumors in dogs. Unfortunately, it’s hard to tell what a lump is with the naked eye. They can vary in appearance and behavior, ranging from benign to malignant.

Early detection and proper diagnosis are crucial to managing skin cancer and improving the outcome for our canine companions.

The following are the five most common types of skin cancer in dogs:

Mast Cell Tumor

Mast cell tumors (MCTs) are a common type of skin cancer in dogs that originate from mast cells, which are part of the immune system.

MCTs can vary in appearance, appearing as raised bumps or masses on the skin. They can occur anywhere on a dog’s body and are more prevalent in certain breeds.

READ: Mast Cell Tumor Dog Life Expectancy

Melanoma

Melanoma is a type of cancer that can affect the skin and other tissues in dogs. They originate from pigment-producing cells and can occur in any area of the body, including the mouth, nail bed, or lightly haired areas exposed to the sun (nose, ears, or belly).

Dogs with darker pigmentation, like Doberman Pinschers, Scottish Terriers, and Labrador Retrievers, may be at higher risk.

It’s important to note that any skin cancer that develops in a dog’s toes or toenails is very painful. Development of melanoma in this area is very serious and may require amputation of the toe or toes.

According to VCA Hospitals, melanomas of the toe are more aggressive. Nearly 30% of dogs have signs that the cancer has spread to other parts of the body at the time of diagnosis.

Common signs of melanoma in dogs include:

• Development of abnormal growths
• Pigmented or discolored skin.
• Dark, irregularly shaped patches or lumps on the skin
• Changes in the size, color, or texture of existing pigmented areas.
• Melanomas can sometimes ulcerate, leading to open sores that may bleed or become infected.
• Melanomas that develop in the toes or nail beds can cause lameness or limping.
• Melanomas can occur in the mouth, gums, or tongue. Look out for signs of bad breath, difficulty eating or swallowing, drooling, or oral bleeding.

The types of melanomas are benign melanocytomas (usually non-aggressive), and malignant melanomas (more aggressive and may spread to other parts of the body.

There is a melanoma vaccine available, but it’s not meant as a preventative. Instead, the vaccine trains the dog’s immune system to right melanoma tumor cells.

Squamous Cell Carcinoma (SCC)

SCC is a type of skin cancer that commonly affects dog. While normally found in the skin, it can also occur in the respiratory tract, digestive tract, and other mucous membranes of dogs (oral cavity, esophagus, and anal region).

Dogs with light-colored or sparse hair (Dalmatians, Beagles, Whippets and Bull Terriers) are more likely to develop SCC of the skin.

Large-breed, dark-coated dogs, however, are more likely to develop SCC of the toes, which is very painful and typically far more aggressive.

The development of these tumors has been attributed to exposure to UV rays or exposure to papilloma-like viruses.

Although these tumors usually appear as singular nodules, they can sometimes present as two or more lesions in multiple areas of the body. This type of SCC is known as Bowen’s disease or Bowenoid carcinoma.

Breeds known to have an increased incidence of squamous cell carcinoma include:

• American pit bull terrier
• Basset hound
• Beagle
• Bloodhound
• Boxer
• Bull terrier
• German shorthaired pointer
• Golden retriever
• Labrador retriever
• Norwegian elkhound
• Standard poodle

Common sites of distant metastasis in dogs include the lungs, liver, bone, and other organs.

Tumors of the Skin Glands

Tumors of the skin glands in dogs can include:

• Sebaceous gland tumors
• Apocrine gland tumors
• Sweat gland tumors
• Anal gland tumors

They can appear as nodules or masses on the skin. Unfortunately, they can sometimes be malignant which is why early detection, accurate diagnosis, and appropriate treatment are important in managing these tumors.

Hair Follicle Tumors

Hair follicle tumors are not considered a direct form of skin cancer. However, they are categorized as skin neoplasms, or tumors. These tumors can affect various parts of the hair follicle including the hair matrix, outer root sheath, or inner root sheath.

Many hair follicle tumors in dogs are benign, meaning they don’t spread to other parts of the body.

Although these tumors are generally slow growing, they still require veterinary attention for diagnosis and monitoring.

Rarely, hair follicle tumors can be malignant. This means they have the potential to invade surrounding tissues and spread to regional lymph nodes or distant organs.

Basal Cell Tumors

Basal cell tumors in dogs are abnormal growths that arise from the basal cells (the deepest layer of the epidermis).

These tumors are typically slow-growing and benign, meaning they do not spread to other parts of the body.

They appear as small, raised nodules or lumps on the skin, ranging in color from pink to dark brown or black, and are most commonly found on the head, neck, shoulders, and limbs of dogs.

They can also develop on the eyelids, where they are known as meibomian gland adenomas.

While basal cell tumors are generally benign, it’s still important to monitor them for changes in size, appearance, or behavior. Regular veterinary check-ups are recommended to ensure proper management and early intervention if required.

How Skin Cancer is Diagnosed in Dogs

The diagnosis of skin cancer in dogs typically involves a combination of physical examination, medical history review, and diagnostic tests.

Physical Examination

During the physical examination, the veterinarian will carefully inspect the dog’s skin, looking for any suspicious lesions, lumps, or abnormalities.

They may also palpate the lymph nodes to check for signs of metastasis.

The medical history review will help identify any relevant information, such as the duration of the skin issue or previous treatments.

Fine Needle Aspirate

In order to get an accurate diagnosis, the veterinarian may perform a fine needle aspirate, where a small needle is used to collect cells from the tumor for examination under a microscope.

Biopsy

In some cases, the veterinarian may biopsy a small sample of the tumor for further analysis.

Imaging

Additional tests, such as imaging (X-rays, ultrasound) or blood work, may be recommended to evaluate the extent of the cancer and assess the overall health of the dog.

The combination of these diagnostic procedures helps veterinarians accurately diagnose and stage skin cancer, allowing for appropriate treatment planning and management.

Skin Cancer Treatment Options for Dogs

The treatment options for dogs with skin cancer vary depending on the type, stage, and location of the cancer. Here are some common treatment options for different types of skin cancer in dogs:

Surgical excision

Surgical removal of the tumor is often the primary treatment for localized skin cancers.

It involves removing the tumor along with a margin of healthy tissue to ensure complete removal. This procedure is typically performed under general anesthesia.

Cryosurgery

Cryosurgery involves the use of extreme cold (liquid nitrogen) to freeze and destroy cancerous cells. It is commonly used for small, superficial skin tumors.

Radiation Therapy

Radiation therapy utilizes high-energy beams to target and destroy cancer cells. It frequently serves as a treatment option for more severe or invasive skin cancers that are resistant to surgery

Radiation therapy may require multiple sessions over several weeks.

Immunotherapy

Immunotherapy is a treatment option that stimulates the immune system to fight cancer cells.

Treatment can be administered orally, through injections, or topically. In some cases, immunotherapy can slow tumor growth, reduce cancer cell spread, and improve the dog’s quality of life.

Not all dogs with skin cancer are suitable candidates for immunotherapy.

The decision to use it depend on things like the type of cancer, stage, and the dog’s overall health. Consultation with a veterinary oncologist is recommended.

Chemotherapy

Chemotherapy involves the use of anti-cancer drugs to destroy cancer cells. It is commonly used for advanced or metastatic skin cancers.

Chemotherapy can be administered orally, intravenously, or topically, depending on the specific drugs and the dog’s condition.

Palliative Care

Palliative care is a way to provide comfort and manage symptoms to improve a dog’s quality of life.

The choice of treatment depends on factors such as the type and stage of the skin cancer, the dog’s overall health, and the veterinarian’s recommendation.

It’s important for dog owners to consult with a veterinarian to discuss the best treatment options for their dog’s specific condition.

• Head and face
• Limbs
• Trunk and torso
• Groin area
• Genital area
• Perianal area
• Mucous membranes (oral cavity, gums, tongue, or other mucous membranes)

Dog Breeds Most at Risk

Breeds with short hair or thin coats, such as Boxers, Bulldogs, Dalmatians, and Pit Bulls, are more vulnerable to skin cancer.

Additionally, dogs that spend a significant amount of time outdoors, especially during peak sunlight hours, have a higher risk.

The sun’s ultraviolet (UV) rays can damage the DNA in skin cells, leading to the development of skin cancer over time.

Breeds at higher risk of developing skin cancer include:

• Boston terriers
• White bull terriers
• Cocker spaniels
• Scottish terriers
• Rhodesian ridgebacks
• Basset hounds
• Labrador retrievers
• Golden retrievers
• Standard schnauzers
• Doberman pinschers

Summary

Skin cancer in dogs is a concerning health issue. However, responsible pet owners can be proactive in protecting pets from the harmful effects of excessive sun exposure.

Unfortunately, pet parents can’t control everything, including genetics. In fact, the most common cause of skin cancer in dogs is genetics.

Regular veterinary check-ups, looking for changes in the skin, and adopting preventative measures can significantly reduce the risk of skin cancer in dogs.

Sources

“Medical Oncology: 5 Types of Skin Cancer in Dogs.” Veterinary Hospital, hospital.cvm.ncsu.edu/services/small-animals/cancer-oncology/oncology/5-types-of-skin-cancer-in-dogs. Accessed 5 June 2023.

“Melanomas of the Skin and Toes | VCA Animal Hospital | VCA Animal Hospitals.” Vca, vcahospitals.com/know-your-pet/melanomas-of-the-skin-and-toes. Accessed 13 June 2023.

North, Straight. “Skin Cancer in Dogs | PetCure Oncology.” PetCure Oncology, petcureoncology.com/skin-cancer-in-dogs. Accessed 5 June 2023.

“Squamous Cell Carcinoma (SCC) in Dogs Explained | the National Canine Cancer Foundation.” Squamous Cell Carcinoma (SCC) in Dogs Explained | the National Canine Cancer Foundation, wearethecure.org/learn-more-about-canine-cancer/canine-cancer-library/squamous-cell-carcinoma. Accessed 13 June 2023.

Lisa Theriault