Skin Cancer In Dogs

Being outdoors is pure joy for many dogs. There are squirrels and rabbits to chase, new smells, and maybe the chance to catch a Frisbee. There is also exposure to ultraviolet rays. However, that should not deter dogs’ outdoor fun. When dogs develop skin cancer, it’s different than what you might think of when you hear of a person having skin cancer. In fact, there are several different varieties of tumors and lumps and skin cancer in dogs. While some are solar-induced due to those UV rays, most of them are not. Genetics are a key factor with certain types, such as mast cell tumors and lymphomas. Fortunately, most lumps on dogs are not cancer at all. In fact, it’s very common for dogs to develop some kind of mass on their skin in their lifetime. Bumps can also originate in subcutaneous tissue (below the skin) and push up to look like and feel like they’re on the skin.

Any breed can develop various types of skin tumors. A dog’s sex isn’t a determining factor, either. A dog could have one tumor, a couple or several all over his or her body. Fortunately, even cancerous tumors can be treated. Treatment can even be curative if the cancer isn’t too aggressive, especially if it’s caught early.

Types of Skin Tumors In Dogs

There are so many different types of skin tumors that the best way to categorize them is as either malignant (cancerous) or benign.

Benign tumors: Some types of benign tumors can still present problems if not treated, depending on their size and location on the body. Pet parents sometimes have benign lumps removed for cosmetic reasons, too. Some of the more common benign tumors include lipomas (fatty tumors); cysts, including follicular cysts; adenomas; basal cell tumors; squamous cell carcinoma in situ; histiocytomas; plasmacytomas; and melanoma tumors. That melanoma is on the “benign” list may be surprising to some, because it’s the most dangerous type of skin cancer for humans. However, about 90% of cutaneous melanomas in dogs are benign. Only through pathology can a veterinarian determine whether a particular tumor is benign or malignant, however. Another skin issue that could be mistaken for cancer is a lick granuloma — a red, raised lesion caused by a dog obsessively licking the spot due to an allergy, anxiety or other reasons. A lick granuloma is not actually a skin tumor, and thankfully they are also benign.

Malignant tumors: Among malignant skin tumors in dogs, mast cell tumors are the most common. They account for about 20% of all canine skin tumors and can be quite invasive. Soft tissue sarcomas are also malignant. They typically form beneath the skin, often in muscle or connective tissue. As they grow, however, a lump may appear to be pushing up from the skin. Other malignant skin tumors include squamous cell carcinoma, hemangiosarcomas, plasmacytomas (which can also be benign), cutaneous lymphomas and malignant histiocytic tumors. A wide range of other types of cancer can also metastasize (spread) to the skin, including breast cancer and bladder cancer.

Signs Of Skin Cancer In Dogs

Canine skin cancer can be difficult to detect. For starters, your dog’s fur may be hiding the evidence. Also, if the cancer hasn’t spread, your dog may not be exhibiting any unusual behaviors like he or she would with a cancer that impacts brain or organ function. In addition to spotting a bump, then, the best way to check for potential tumors is by feel — by petting your dog as a way of examining him or her. (As a side note, while feeling for lumps on the skin, it won’t hurt to check areas where lymph nodes are located, such as under the jaw, in the armpits and in the groin area and behind the knee region. Swollen lymph nodes could be a sign of another type or cancer or other medical issue.)

Another signal that a tumor may be present is a dog constantly licking one area. Dogs lick things that are abnormal, so even if a bump isn’t itchy or painful, its mere presence might prompt excessive licking. Remember that if there is a lump, it doesn’t mean it’s cancer. If you’re aware of a lump that your dog has had for a while, there a good chance it’s not cancer, but you shouldn’t rule it out without a visit to the vet.

Workup & Diagnosis

A suspicious lump under a dog’s skin or on the skin merits a closer look by a veterinarian. Your vet will likely look at and feel the lump and may have an initial inclination as to whether it is cancerous, but the first step in determining for sure is to perform an aspiration. This procedure consists of using a needle to withdraw a small sample of cells or tissue. The sample is sent to a pathologist, who examines the sample under a microscope in an attempt to determine what the lesion is and whether the tumor is benign or malignant.

Aspiration cytologie for skin cancer yield a diagnosis about 75% of the time. Sometimes a second aspiration is needed if the first is inconclusive. Alternatively, the veterinarian could recommend a biopsy. One type, an incisional biopsy, removes a slice or piece of the tumor. A biopsy can also involve an excision of the full tumor. As a biopsy almost always involves anesthesia, your veterinarian likely also will order bloodwork, urinalysis and chest X-rays to make sure your dog is healthy enough to handle anesthesia. Your vet will also want a complete workup if he or she has reason to believe the tumor is malignant. X-rays can help determine whether the cancer has spread to the lungs. As some cancers can spread to the regional lymph nodes, aspiration or biopsy of an enlarged lymph node is also recommended.

Treatment & Prognosis

Treatment protocols differ for different types of skin cancer in dogs. The basic approaches can be generalized, however.

For benign tumors: When aspirating a tumor is enough to determine that it is benign, it’s possible that no treatment will be needed. The veterinarian also may document the size of the bump and use subsequent visits to monitor growth and suggest treatment later as indicated. For example, if a lipoma (fatty tumor) grows from the size of a dime to a half-dollar, removal might be suggested. If the lipoma growly quickly to the size of an orange or grapefruit, surgical excision may be highly recommended. Some pet parents want benign tumors removed regardless, due to cosmetic reasons. There are also instances were removal of a benign skin lump is recommended because it’s in a precarious area, such as the underarm, where it may cause a dog discomfort or limit his or her range of motion. Another example is if the lump is a sebaceous cyst. Because they can be red and raised and can rupture or ooze, perhaps making the dog want to lick that spot, removal is an option. Antibiotics may also work but on occasion they don’t. Though benign, a lump can also signal a related medical issue requiring treatment. A benign plasmacytoma, for example, could indicate a systemic issue such as multiple myeloma.

For malignant tumors: If the tumor if localized, surgery is often the first recommended treatment for skin cancer in dogs. The goal is to remove all of the cancer by excising the mass and achieving wide “clean” margins, meaning the tissue around the outer edges of the removed portion shows no cancer, indicating the malignancy has been removed. For some tumors, surgery is curative. For other tumors, surgery may be followed up with radiation therapy. There are also circumstances where surgery may not be recommended at all, and radiation becomes the primary treatment.

There are two primary types of radiation therapy. Conventionally fractionated radiation therapy (CFRT) targets the tumor, typically over 15 to 21 treatment sessions. Stereotactic Radiation, a more innovative approach, reduces that to one to three sessions, using a higher dose of radiation and even more precise targeting that minimizes damage to surrounding healthy tissue. PetCure Oncology specializes in Stereotactic Radiation treatments.

If a mass is terribly aggressive or there are signs of spread into the lymphatic or vascular system or spread to other areas of the skin or internal organs, a more comprehensive approach may be taken. This could involve radiation and/or chemotherapy treatment (+/- surgery) under the guidance of a veterinary oncologist.

Even with treatment, some types of skin cancer will come back, but a dog may do very well for several months or a year or so. Very aggressive cancers, on the other hand, might spread in a period of a few months. In those instances, decisions will have to be made based on the dog’s quality of life.

Find A PetCure Oncology Location Near You

When it comes to treating skin cancer in dogs, PetCure Oncology has the experience, expertise and range of innovative treatment options a pet parent would want. We understand the love that pet parents feel for their dogs, and that’s why we make it our mission to offer superior care, extend your time together and provide the best quality of life possible. Our professionals are truly compassionate and supportive. For more information about PetCure Oncology and our treatment options, find a location near you today.

Types of Cancers in Dogs

If your dog is displaying any symptoms of cancer or has been diagnosed with cancer, sort below by cancer type or tumor location to learn more about the most common types of cancer in dogs and available treatment options. Click on the links for more specific information on treatment and real patient stories.


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