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The dog owner’s guide to canine skin cancer

Vet examines fluffy dog for skin cancer tumors

Just like humans, dogs can develop all kinds of cancer, including skin cancer. Not all growths or lumps that you may find under your pup’s fur are malignant. However, skin cancer can be dangerous. It should be addressed by a veterinary professional as soon as possible. 

The American Kennel Club (AKC) notes that skin tumors are the most commonly diagnosed type of tumor in dogs. Fortunately, skin tumors can be seen on the body relatively easily. This means it is possible for skin tumors to be caught and treated before they progress. There are several different types of aggressive cancerous skin tumors all with a variety of potential causes and symptoms. It’s important for pet parents to understand what to look for, what to do when they suspect their dog has skin cancer, and how to prevent skin cancer. 

Table of contents: 

Types of more aggressive canine skin cancer 

Malignant melanoma 

These cancerous tumors are most commonly found on the lips, mouth, and nail beds. The head, neck, and scrotum areas are also moderately predisposed to skin cancer. They are often dark-pigmented or can lack pigment entirely. Melanomas typically look like raised lumps and are often ulcerated. They are not as common as benign tumors, but are a serious concern. Malignant melanomas grow quickly and have a high risk of metastasis. 

Mast cell tumors 

Mast cell tumors are the most common types of skin tumors found in dogs, according to the National Canine Cancer Foundation. These tumors can develop anywhere on a dog’s body and even in internal organs. Mast cell tumors are most commonly found on the limbs, lower abdomen, and chest. They can also develop in dogs of all ages, but occur most often in dogs between eight and 10 years old. Small mast cell tumors may remain quiet and seem inactive for long periods before spreading. 

Squamous cell carcinoma 

Squamous cell carcinoma is also a commonly diagnosed skin tumor dogs, and primarily affects senior pups. These tumors originated in the epidermal layer of a dog’s skin and typically show up on the head, lower legs, rear, and abdomen. They can also develop in the nail beds, paw pads, and nose. 

According to VCA Animal Hospital, squamous cell carcinoma is more common in sparsely-haired dogs with light-colored hair and skin. This includes Dalmatians, Beagles, Whippets, and white Bull Terriers. Large-breed, dark-coated dogs such as Labrador Retrievers and Rottweilers are more prone to developing squamous cell carcinoma on their toes. 

Symptoms of skin cancer in dogs 

The symptoms of dog skin cancer can vary greatly depending on the type of cancer. Generally, pet owners may notice an unusual lump or area of discoloration on their pup’s skin. According to AKC, some of the first signs of skin cancer typically involve changes in the size, shape, color, or ulceration of a growth or lump. 

Signs of malignant melanoma 

Cases of malignant melanoma in dogs most commonly occur on the toes (digits) and in the mouth (oral). Melanomas in the paw pads and nail beds may appear as toe swelling and redness. They may even be black in color. Advanced digit tumors can result in the loss of the affected toenail and destruction of the underlying bone, so owners may notice limping. According to the national Canine Cancer Foundation, 50 percent of these tumors spread to other parts of the body. Dogs with digit melanomas often develop a secondary infection, too, making diagnosis and treatment challenging. 

In cases of oral melanomas, pups may exhibit an increase in salivation and even loose teeth. These tumors are often black or pink, and can also spread rapidly to areas including the lymph nodes and lungs. 

Signs of mast cell tumors 

According to the Merck Veterinary Manual, mast cell tumors can form masses that range in size from one millimeter to three or more centimeters. These tumors typically redden when you touch or bother them. They may appear larger and smaller at different times due to swelling. Mast cells are involved in allergic reactions and can release histamine. This means these tumors can cause irritation and itchiness, resulting in a lot of scratching or chewing in the area. 

Signs of squamous cell carcinoma 

Squamous cell carcinoma in dogs may appear as raised bumps or a white skin mass. Eventually, these tumors may begin to die off in the center. This causes it to resemble an open sore that occasionally bleeds, according to the Merck Veterinary Manual. While these tumors are typically less aggressive than melanoma, they can destroy much of the tissue in the affected area.  

Digit squamous cell carcinoma can be very painful for pups—you may notice that your dog is reluctant to go for walks, and they may leave behind blood on the floor or on their toes. These tumors can be very itchy. Your pup may attempt to lick or chew the affected toe(s) aggressively, potentially leading to the loss of toenails. 

Causes of canine skin cancer 

Canine skin cancer can have a wide variety of causes. Veterinary experts at VCA Animals Hospitals note that genetics play a large role in determining whether a pup is likely to develop cancer. In fact, a dog’s genetics are the number one risk factor for skin cancer, and many cancers are indeed the result of a genetic predisposition. 

Some dog breeds are more prone to certain forms of skin cancer. For example, Miniature and Standard Schnauzers and Scottish Terriers are at an increased risk of developing malignant melanoma than other breeds. AKC notes that Boxers, Pugs, Rhodesian Ridgebacks, and Boston Terriers seem to be particularly susceptible to having mast cell tumors at some point, while Bloodhounds, Basset Hounds, Poodles, and Norwegian Elkhounds are more prone than other breeds to squamous cell carcinoma. 

Just like for humans, too much sun exposure can increase a pup’s chances of developing skin cancer. This is particularly true for short-, fine-haired dogs with light-colored skin visible on their bellies, such as Chihuahuas and Greyhounds. According to VCA Animal Hospitals, squamous cell tumors can be caused by overexposure to harmful UV rays. 

Other triggers for dog skin cancer can include exposure to harmful chemicals in their environment, hormonal abnormalities, and certain types of viruses. The exact causes of mast cell tumors are not known, but VCA notes that this form of skin cancer has been linked to skin irritants, inflammation, and genetic factors. 

Treating cancerous skin tumors 

The great news is that many types of canine skin cancers are treatable if they are detected early. Experts from VCA Animal Hospitals note that treatment strategies determined by a veterinarian will depend on a few factors, including the type, size, and location of the tumor, the dog’s overall health and breed, as well as the stage of the cancer. 

Some skin tumors can be removed surgically, which AKC notes is often the most effective treatment method. If your dog is diagnosed with skin cancer, your veterinarian may recommend radiation and or chemotherapy. Again, these options vary depending on the type of cancer—malignant melanomas, for example, are resistant to radiation therapy while mast cell tumors are more sensitive. 

How to prevent dangerous lumps on your dog’s skin 

Canine skin cancer can be a complex and costly health issue to treat. With this, early detection and prevention are crucial. The Merck Veterinary Manual advises that, in general, the best thing pet owners can do to catch skin cancer early is to keep an eye on any strange lumps or bumps on their dog’s body, especially as they age. Familiarize yourself with your dog’s skin so that you can more easily detect any potentially dangerous changes that may indicate the development of skin cancer. 

While it’s important to be able to identify potentially cancerous skin developments, it is also important to know what irregularities on your dog’s skin are harmless and shouldn’t be worried about. Cancerous growths and lumps are not to be confused with benign bumps, such as fatty deposits, skin tags, , warts and other benign adenomas associated with the follicles or glands in the skin. Instead, be on the lookout for dark spots or irritated patches of skin, as well as lumps or bumps. 

The skin cancer risk factor most in your control as a pup parent is your dog’s exposure to harmful UV rays from the sun. Pups, particularly light-skinned and short-haired breeds, should have limited sunlight exposure, particularly on areas of their body with little to no hair, like the nose, tummy, and paw pads. When staying out of the sun isn’t an option, pet owners may consider using protective apparel and or topical sunscreen specifically formulated for and safe to use on dogs. 

Talk to your veterinarian about other ways to prevent your pup from developing skin cancer. 

Any health or medical information in ElleVet blogs is from a variety of public and reputable sources. This information is intended as an educational resource only and is not a substitute for expert professional care.