Skin Cancer In Dogs: Everything You Need To Know

Skin Cancer In Dogs: Everything You Need To Know

Skin cancer in dogs

The last thing any pet owner wants to hear is that their furry friend has cancer. It's an intimidating and unfortunate reality for many dogs. Fortunately, skin cancers are much easier to treat than other forms of cancer, and the outlook is usually good. In this article, we'll go over the different kinds of skin cancer that dogs can develop, as well as the different options and possible treatment options available.


1. What Is Skin Cancer In Dogs?
2. The Different Types Of Skin Cancer In Dogs
3. Mast Cell Tumors In Dogs
4. Lifespan of Dogs With Mast Cell Tumors
5. Soft Tissue Sarcomas
6. Leukemia In Dogs
7. Lymphoma In Dogs
8. Epitheliotropic Lymphoma In Dogs
9. Melanoma In Dogs
10. Squamous Cell Carcinoma In Dogs
11. Skin Gland Tumors In Dogs
12. Hair Follicle Tumors In Dogs
13. Basal Cell Cancer In Dogs
14. Symptoms Of Skin Cancer In Dogs
15. What Does Skin Cancer In Dogs Look Like?
16. How To Tell If A Mole Is Cancerous
17. Diagnosing Skin Cancer In Dogs
18. Treatment For Skin Cancer In Dogs
19. Preventing Skin Cancer In Dogs

What Is Skin Cancer In Dogs?

While cancer is an unpleasant reality that no pet owner ever wants to consider, it's unfortunately common. 25% of dogs will develop some form of cancer throughout their lives, and 50% of dogs over the age of ten are likely to pass away due to cancer.

Of the types of cancers a dog can get, skin cancer is one of the most common. The term "skin cancer" covers a wide range of conditions, though they overlap and share similarities across the board. Cancer occurs when an abnormal or deformed cell begins to multiply. These cells begin to form masses and can spread throughout your dog's body.

Skin cancers are, as you would expect, when these abnormalities develop along your pet's skin. They can also show themselves in other places, like hair follicles and their nails. If you notice any abnormalities that you believe could be cancer, contact your vet immediately.

The Different Types Of Skin Cancer In Dogs

As mentioned, skin cancer is an umbrella term that encompasses a wide range of cancers. Skin cancers can be difficult to spot in dogs because their bodies are covered in hair. However, this doesn't mean that they are any less likely to develop issues with skin cancer.

The reason that there are so many different types of skin cancers in dogs is that there is so much variety on the surface of your dog's body. They have skin, hair, nails, follicles, different textures and areas of their skin. Each of these will influence how skin cancer develops and spreads.

In order to walk you through the scope of skin cancer and the many forms it can surface in, we'll go through the most common types of skin cancer that your dog can be diagnosed with. This will help you develop a better understanding of the issue as well as understand how a vet will diagnose your pet.

Benign and Malignant Tumors

A tumor is a growth that forms due to cancerous cells. Cancerous cells are deformed and abnormal cells that begin to multiply within your pet's body. As they grow in number, they clump together, becoming what is known as a tumor. Tumors fall into two primary categories: benign and malignant.

A benign tumor is one that does not spread or invade other areas of your pet's body. It simply grows in one place, at its own rate. Benign tumors the less dangerous of the two, however they can still pose a threat. Generally, all that it takes to solve a benign tumor is to remove it from your pet's body through surgery.

Malignant tumors, on the other hand, are tumors that actively spread and make their way throughout your pet's body. These kinds of tumors can be extremely dangerous for your pet's health, causing damage to surrounding tissue and other areas in your dog's body.

Mast Cell Tumors In Dogs

Mast cell tumors are a form of skin cancer in dogs that occur in, as the name would suggest, the mast cells. Mast cell tumors are the most common form of skin cancer in dogs, though it can affect other areas like your dog's spleen, bone marrow, liver, and gastrointestinal tract.

They usually appear as a lump just on or below your pet's skin. These lumps can change in size, both shrinking and growing. This is due to degranulation, which means that the tumor is releasing granules into your pet's bloodstream. This can be dangerous and is a result of irritation in the tumor. In addition to degranulation, you may notice that these lumps become red, irritated, and swollen.

Once they appear, mast cell tumors can spread to other areas of your pet's body. Sometimes they remain benign for months, not growing or spreading. Other times they can be very malignant, spreading and growing rapidly.

Lifespan of Dogs With Mast Cell Tumors

Mast cell tumors fall into three categories. These categories serve to differentiate how severe the tumors are and how likely they are to cause harm to your dog.

Grade I

Grade I mast cell tumors are considered benign and make up about 36% of MCT diagnoses. They have a less defined shape, which can make them difficult to spot and remove. Dogs with Grade I MCTs are generally safe.

Grade II

Grade II MCTs are slightly more common, making up 43% of MCT diagnoses in dogs. They're also the most common and can be cured with surgery 65% of the time. However, resurgence and spreading are fairly common, so dogs with Grade II MCTs have a high likelihood of redeveloping them in the future.

Grade III

Grade III MCTs are the rarest, and the most dangerous. They occur in 20% of MCT diagnoses. They are aggressive and spread rapidly. Treatment with chemotherapy is possible, though the prognosis is usually poor.

Soft Tissue Sarcomas

Soft tissue sarcomas are malignant tumors that form on or just beneath the surface of your pet's skin. They can be visible externally or exist within the connective tissues under your pet's skin, like their muscles, fats, and cartilage.

Sarcomas give the impression of being self-contained and singular, though they often hide a large spread of tumors that have already invaded the patient's body. It's not uncommon for sarcoma tumors to come back after they've been surgically removed.

For the most part, however, sarcomas have a low chance of spreading. Most dogs diagnosed with sarcoma have a high life expectancy and can be treated with aggressive surgeries. In more severe cases, however, chemotherapy and radiation therapy might be required. Vet's say that within three years of being diagnosed, 85% of dogs are tumor free.

Leukemia In Dogs

Dogs with cancerYou've likely heard of leukemia's reputation in humans, and unfortunately, it shares a similarly negative reputation among our canine companions. Canine leukemia occurs when cancerous cells begin reproducing in the early and intermediate stages of their lifespan. In doing so they are able to make their way into your pet's bloodstream and spread throughout their body extremely quickly.

Leukemia cells can invade your pet's vital organs as well as their bone marrow, making it very difficult to remove. Dogs with leukemia will have seriously compromised immune systems. This is because on top of having to fight cancer, your dog's white blood cells will also be damaged by chemotherapy. If your dog is going through leukemia, it is important that they stay in a sanitary and contained environment. Simple sickness like the flu can be fatal for dogs with leukemia.

Lymphoma In Dogs

Lymphoma in dogs is very similar to cases of lymphoma in people. It's a form of skin cancer that invades your pet's lymphocytes. Lymphocytes are white blood cells that your dog's body uses to fight off infection. When a dog develops lymphoma, these cells become cancerous, affecting other aspects of your dog's system like their spleen, bone marrow, and lymph nodes.

There are over 30 types of lymphoma lymphoma in dogs, though the most common four are:

  • Extranodal lymphoma
  • Alimentary lymphoma
  • Multicentric lymphoma
  • Mediastinal lymphoma

Each of these varies in aggressiveness, survival rates, and symptoms. The most common one is multicentric lymphoma, which makes up 85% of lymphoma diagnoses in canines. Multicentric lymphoma affects your dog's lymph nodes, which can usually be seen as growths around their neck, shoulders, or legs.

Epitheliotropic Lymphoma In Dogs

One of the rarer forms of lymphoma in dogs is epitheliotropic lymphoma. This form of lymphoma affects only 1% of the canine population, so the majority of pet owners will not be faced with this diagnosis. However, it is an extremely severe form of lymphoma with a dire prognosis.

Epitheliotropic lymphoma will usually present itself in four primary ways. The first is red, inflamed, and flaky skin. The flaky skin can be so severe that it appears to break off in sheets. It can also cause loss of pigmentation as well as crusting around sensitive areas like your dog's nose, eyes, and mouth.

Other signs that your pet has this form of lymphoma are lumps on the surface of their skin and thickening around their oral tissue. These four signs should be taken seriously, and warrant an immediate trip to the vet.

Melanoma In Dogs

Melanoma is a fairly common form of skin cancer in both dogs and people. It affects pigmented cells called melanocytes, usually creating small, singular spots on your dog's skin, usually as moles. The majority of the time these are benign, and will not spread to other tissues.

There are cases, however, where melanomas can become malignant. Malignant melanoma tumors around your pet's oral region, though it is possible for them to grow in areas that are covered by hair. If a melanoma tumor is malignant, there is a high likelihood that it will spread to your dog's organs.

There is no clear cause as to why melanoma develops, though there are a few guesses. Genetics, for example, are believed to play a big role in the development of melanoma. Another thought is that trauma or frequent licking in a particular area of your dog's skin can cause melanoma to develop. This is because both of these factors require cell multiplication, increasing the odds of melanoma development.

Squamous Cell Carcinoma In Dogs

While the name is a bit of a mouthful, this type of cancer is most likely what comes to mind when thinking about skin cancer. It's caused by overexposure to UV rays (sunlight), and as a result is more common in dogs that live at high altitudes. Dogs that spend a lot of times outdoors are at a higher risk of developing this type of cancer, as well as breeds like Dalmatians, Beagles, Whippets, Boxers, and Poodles.

Squamous cell carcinoma appears on the surface of a dog's skin, usually as a white colored growth of skin. It can also appear as crusty, bleeding sores. If you notice a sore on your pet that doesn't go away over time or with medical treatment, it could be related to this type of skin cancer. This type of skin cancer can usually be prevented by limiting the amount of time your dog spends outdoors, especially during hot periods of the day.

Skin Gland Tumors In Dogs

Skin gland tumors, also known as adenocarcinomas, are a glandular form of skin cancer in dogs. Your dog's sebaceous glands (where these tumors develop) are responsible for secreting sebum, keeping their skin and coat oily. Tumors in these glands are fairly common in dogs, particularly when they are older. While there is no known cause for these kinds of tumors, there are genetic predispositions in breeds like Malamutes, Dachshunds, and Poodles.

Skin gland tumors are usually found near your dog's head and grow outwards. This makes them pretty easy to spot and show to your vet. They can be black or brown and are only a few millimeters in diameter. If you spot them, take your dog to a vet to have them diagnosed. There are many types of skin gland tumors, and a vet will need to determine their type to set up a treatment plan for your pet.

Hair Follicle Tumors In Dogs

Hair follicle tumors are usually benign and originate in a few different ways. Sometimes a hair follicle closes up, forming a sac, which can lead to tumor development. In other cases, tumors can come from the cells that make up your dog's hair follicles.

Hair follicle tumors are almost always harmless, though that doesn't mean you should hold off visiting the vet. Your dog's veterinarian will remove the tumor via surgery, usually taking out a more generous area of tissue than required. This is to ensure that the tumor does not spread or reappear after surgery.

Because your dog has hair all over their body, these kinds of tumors can develop almost anywhere on their skin. Even though the prognosis for dogs with hair follicle tumors is pretty good, you should still keep a close eye on your dog after surgery. Cancers always have the possibility of resurfacing and should be taken seriously.

Basal Cell Cancer In Dogs

Basal cell cancer is another one of the most common skin cancers in dogs. Somewhere between 3% and 12% of all skin cancer diagnoses in dogs is related to basal cell cancer. They typically occur in older dogs and develop in the lower layers of your pet's skin.

Basal tumors can be both benign and malignant, so it's important that a vet examines these growths to determine their severity. That said, malignant basal tumors are pretty rare; less than 10% of these tumors ever spread. These tumors typically appear on your dog's neck, head, and shoulders.

Basal tumors in dogs will look like a single, raised mass on your dog's skin. They are hairless and usually well-defined. This makes them easy to spot and remove. If they're small enough, they may be able to be removed with freezing, so there isn't always a need for surgery.

Symptoms Of Skin Cancer In Dogs

The symptoms your dog exhibits when it comes to skin cancer will depend on which kind of skin cancer they have. Typically, the different forms of skin cancer will be most visible through tumors on or just underneath their skin. Depending on the location of these tumors, they could cause pain or discomfort for your pet.

Other times skin cancer will appear as discoloration and moles along your dog's skin. It's worth noting, though, that not all skin tumors are skin cancer. Some are completely benign, like skin tags, and pose no threat to your dog's well being. That said, you should always take your pet to a veterinarian if you notice any abnormalities along their skin's surface.

What Does Skin Cancer In Dogs Look Like?

Skin cancer will primarily look like two different things. The first is as a discoloration in your dog's skin, most commonly a mole. The second is as a tumor, which will vary in size, shape, and location, depending on which type of skin cancer is causing the tumor.

Discolorations and moles are known as melanomas, named so because of their pigmentation. They're usually very small, only a few millimeters in size. They can grow to be bigger, however. Tumors can be mast cells, which look like rubbery lumps or growths under or on your dog's skin. They can also be carcinomas, which look like warts.

How To Tell If A Mole Is Cancerous

Moles can be tricky to diagnose on your own because they are usually benign. This means that cancerous ones will go unnoticed or ignored until they have already become a serious threat. If you can, take your pet to a veterinarian as soon as you notice a new mole, just to stay on the safe side.

While only a trained professional can determine if a mole is benign or cancerous for sure, there is a rule that can help you reach a conclusion on your own.

This rule is known as the ABCDE rule:

  • Asymmetry: The mole is asymmetrical, meaning one half doesn't match the other
  • Border: The border of the mole is irregular, ragged, or blurry
  • Color: The mole is not uniform in color
  • Diameter: The mole is larger than 6mm in diameter, roughly the size of a pencil eraser
  • Evolving: The mole is changing in size, shape, or color

Diagnosing Skin Cancer In Dogs

Fine needle aspiration is the most common way of diagnosing skin cancer in dogs. This involves taking a fine point needle, sampling a few of the cells from the tumor or melanoma, and examining it under a microscope. Another common method that vet's use to determine if a cell is cancerous is through a biopsy, which involves cutting a small portion of the growth off and examining it.

Your vet may also conduct a histology and cytology, both of which allow them to view the tissue of the abnormality. Using these tools they can examine the architecture of the growth and make their assessment.

Treatment For Skin Cancer In Dogs

The method used to treat your dog's cancer will vary greatly depending on a few factors. The type, severity, and spread of your dog's skin cancer will all warrant different treatment methods. If the growth is on the outside of their skin, small, and benign, then your vet may remove simply by freezing it off.

If the growth is more severe but still benign and solitary, then your vet can likely remove it through an excision. This involves removing the tumor as well as some of the surrounding tissue, to prevent resurfacing.

If the skin cancer is malignant and spreading - or already has spread - throughout your dog's body, then chemotherapy or radiation therapy may be required. The outlook for dog's with skin cancer is pretty good since most of them are benign and near the surface. However, there are some that spread quickly and can put your dog's health in serious danger.

Preventing Skin Cancer In Dogs

Unfortunately, because the cause of most forms of skin cancer is largely unknown, there is no one way to prevent your dog from developing it. The majority of skin cancers seem to be caused primarily by genetic factors. Some breeds, particularly pedigree breeds, have a much higher chance of getting skin cancer than others. As of now, the only way to prevent this would be to stop breeding these higher risk breeds.

Some skin cancers are caused by exposure to UV rays, which pet owners do have some control over, fortunately. If you live in a high altitude area, your dog is at a higher risk of developing skin cancer from UV rays. Keep them indoors when you can, and limit their outside play during brighter times of day (typically high noon).


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