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Skin Cancer in Dogs

What is Skin Cancer in Dogs?

Skin cancer in dogs refers to an abnormal proliferation of skin cells, with the term “cancer” often associated with malignancy. However, not all instances of skin cancer in dogs are malignant; some are benign growths that pose no significant threat beyond the tumor itself. Malignant tumors are characterized by their ability to metastasize to other parts of the body via the bloodstream or lymphatic system, while benign masses do not exhibit such invasive behavior.

Similar to humans, sun exposure, particularly to UV radiation, can elevate the risk of skin cancer in dogs. Breeds with lighter-colored fur and skin are particularly susceptible to certain types of skin tumors. While sun exposure is a significant risk factor, the precise causes of skin tumors in dogs remain subject to further research. Some tumors have a genetic predisposition, such as the prevalence of mast-cell tumors in breeds like Boxers, Bulldogs, Boston Terriers, and Pugs. Additionally, viral infections can contribute to the development of certain growths.

Encountering a lump on your dog should not immediately incite panic. Numerous factors can cause lumps, and thankfully, many are benign or easily treatable. The crucial step is to remain vigilant in monitoring your pet for any lumps or bumps and promptly inform your veterinarian of any discoveries.

Types of Skin Cancer in Dogs

Benign Skin Cancer in Dogs

  • Lipomas: These tumors typically reside just beneath the skin’s surface and originate from fat/lipid cells. Lipomas are usually soft and pliable (fluctuant) and are typically not attached to underlying structures. While they can start as small as a grape, lipomas have the potential to grow to the size of a watermelon.
  • Histiocytomas: Found predominantly on the limbs of younger dogs, typically those under 2 years old, histiocytomas arise from a cell type known as a Langerhans cell, which is part of the immune system. Often referred to as “button tumors,” they are small, round, raised, hairless pink masses. Larger-breed dogs like Labrador Retrievers, American Staffordshire Terriers, and Boxers commonly experience histiocytomas, which typically regress on their own within approximately three months.
  • Papillomas: Resembling wart-like growths, papillomas frequently manifest around the mouth or eyes of younger dogs or those with immature or weakened immune systems. They are caused by the canine papilloma virus (CPV1) transmitted through the pet’s environment, usually via food or water bowls. Papillomas typically take 1 to 2 months to develop and often disappear within the same timeframe.
  • Sebaceous Adenomas: Originating in oil glands within the skin, sebaceous adenomas present as raised, hairless bumpy masses, usually the size of a pea or blueberry. They are more prevalent in older, light-colored dogs, particularly small breeds such as Poodles, Shih Tzus, and Maltese.

Malignant Skin Cancer in Dogs

  • Mast Cell Tumor: Mast cells, integral to the immune system and allergic reactions, release histamine during allergic responses. Mast cell tumors (MCT) can lead to mass degranulation, causing significant histamine release and resulting in swelling, itchiness, irritation, and potentially life-threatening allergic reactions. These tumors typically appear as raised red lumps, sometimes ulcerated, with surrounding tissue swelling. Mast cell tumors are the most prevalent skin tumor in dogs, occurring most frequently around the age of 10. Common breeds susceptible to MCT include Boxers, Boston Terriers, Bulldogs, Pugs, Staffordshire Terriers, Labradors, Golden Retrievers, Rhodesian Ridgebacks, and Weimaraners.
  • Squamous Cell Carcinomas: Originating from the epidermis or skin cells, squamous cell carcinomas (SCC) are common in older animals, particularly those with lighter skin and shorter fur. They often develop on the noses of dogs spending extended periods outdoors. SCC appearance varies widely, usually appearing as red or ulcerated skin masses. Crusting and erosion may also occur. SCCs are also the second most common oral tumor in dogs, affecting the gums or tongue.
  • Melanomas: Arising from melanocytes responsible for skin coloration, melanomas are typically pigmented, appearing black or brown. They are commonly found in areas with less hair, such as around the mouth, feet, and eyes. Melanomas of the toes, prevalent in black dogs, may begin as swelling around a toenail. Melanomas are also the most frequent oral tumor in dogs, characterized by rapid growth and high metastatic potential.
  • Fibrosarcoma: Developing from connective tissues of the skin and beneath it, fibrosarcomas often occur on the legs of middle-aged or older dogs. They typically present as firm lumps on or under the skin, sometimes appearing in multiples in one area. Associated symptoms may include pain, swelling, bleeding, and infection, particularly if the masses open. Fibrosarcomas can also manifest around the mouth and nose.


The primary indicator of skin cancer in dogs is a noticeable alteration in your pet’s skin. Thankfully, this change is typically conspicuous, allowing for early detection of lumps or growths. This alteration often presents as a new growth, lump, or bump, and in some cases, it may manifest as a persistent sore that fails to heal. Regardless of their size, color, location, consistency, or the presence of fur, all new lumps and bumps should undergo evaluation by a veterinarian. This proactive approach ensures timely diagnosis and appropriate management of potential skin cancer in dogs.


Skin cancer in dogs is characterized by uncontrolled growth of masses originating from various cell types within the dog’s skin. The precise reasons why cells lose their normal regulatory mechanisms and begin to replicate uncontrollably are not fully understood. Similar to humans, sun exposure, particularly to UV radiation, heightens the risk of skin cancer in dogs, particularly those with lighter skin tones.

While sun exposure is a significant risk factor, comprehensive studies are required to elucidate the underlying causes of skin tumors in dogs. Identified factors contributing to the development of skin cancer in dogs include genetic predispositions, such as mast cell tumors, and viral infections, such as papillomas. Understanding these causes is crucial for advancing prevention and treatment strategies for skin cancer in dogs.


Any observable changes in lumps on your pet’s skin, including growth, irritation, bleeding, changes in size or color, or persistence for a month or more, warrant examination by your pet’s primary care veterinarian. Different diagnostic procedures may be recommended based on the nature of the lump, as many tumors share similar external appearances, underscoring the importance of thorough examination by the veterinarian.

A needle biopsy is typically the initial diagnostic step, where a sampling of cells is collected from within the mass for evaluation. This process, also known as Fine Needle Aspiration (FNA), involves inserting a needle into the mass to extract cells, which are then examined under a microscope. While needle biopsies often yield precise diagnoses, they may not always provide a comprehensive assessment of the mass.

Some cases may necessitate sedation for the biopsy procedure, depending on the mass location and the pet’s temperament. In instances where a larger tissue sample is required, a punch or tissue biopsy may be performed, involving the removal of a section of the mass or the entire mass for evaluation in a lab. Local anesthesia, sedation, or general anesthesia may be administered based on the patient’s needs and tumor location.

For suspected malignant tumors, radiographs or X-rays may be recommended to monitor for signs of metastasis, particularly in the lungs, which are common sites for tumor spread. Advanced imaging techniques such as CT scans, MRIs, or ultrasound may be employed to assess deeper tumors or examine lymph nodes for signs of metastasis.

These diagnostic measures play a crucial role in determining the extent and nature of skin cancer in dogs, facilitating appropriate treatment planning and management strategies.


Given the diversity of skin tumors and the individual characteristics of each case, treatment approaches should be tailored to your pet, considering factors such as tumor type, stage, and location. Fortunately, many skin tumors are manageable, particularly when detected early. Treatment typically involves a combination of the following options: surgery, chemotherapy, radiation therapy, or immunotherapy.

Each treatment modality aims to address specific aspects of the tumor and its potential spread, with the ultimate goal of minimizing disease progression and improving your pet’s quality of life. By customizing treatment plans based on the unique features of the tumor and your pet’s overall health, veterinarians can optimize therapeutic outcomes and enhance the prognosis for dogs with skin cancer.


In the management of most skin tumors, particularly those in small and readily accessible body areas, surgical excision serves as the primary treatment approach. This procedure aims to eliminate the majority, if not all, cancer cells from the affected area. Surgery can be curative, indicating that removal of the mass alone suffices as treatment (as seen with small benign masses like sebaceous adenomas), or it can constitute a component of a comprehensive treatment regimen (such as with melanomas, where metastasis is frequent).


Chemotherapy entails the administration of medications either intravenously (IV) or orally. These drugs target cells that divide rapidly, including those contributing to tumor growth. Chemotherapy is frequently employed for specific types of cancer that affect multiple areas in the body or following the surgical removal of a mass already suspected of spreading.


Radiation therapy employs a focused radiation beam to target specific tumors, particularly those situated in areas where surgical removal is challenging. It is commonly utilized in conjunction with surgery or chemotherapy as part of a comprehensive treatment approach.


Immunotherapy operates akin to a vaccine. Specifically designed for certain cancer types, such as melanomas, immunotherapy involves the administration of a vaccine containing inactivated components of cancerous cells. These components circulate through the pet’s system, prompting its immune system to combat cancerous cells. Immunotherapy is typically integrated with one or more other treatment modalities to enhance its efficacy.

Recovery and Management

The recovery and management of skin cancer hinge largely on the specific type of tumor identified. Your veterinarian will assess diagnostic results and discuss the recommended treatment and prognosis for your pet. In some cases, they may refer you to a veterinary oncologist for specialized care.

Following surgery, your dog may experience discomfort, and your veterinarian is likely to prescribe pain medication. It’s crucial to adhere strictly to all medication instructions provided. Many patients will require crate rest, and your veterinarian will offer guidance on the timeframe for returning to normal activity levels.

If chemotherapy is incorporated into your pet’s treatment regimen, it may induce side effects such as nausea, vomiting, diarrhea, and fatigue. Your veterinarian may prescribe anti-nausea medications or other supportive therapies to mitigate these effects during chemotherapy sessions. Additionally, ensuring your pet receives high-quality nutrition is essential to facilitate a speedy recovery process.


To mitigate the risk of skin cancer, it’s advisable to minimize your pet’s sun exposure, especially during peak UV hours. Pets with light-colored fur or short coats may benefit from the application of dog-specific sunscreen.

Early detection plays a pivotal role in addressing many types of skin tumors. It’s imperative to diligently monitor your pet for the emergence of lumps and bumps on their skin and take an active role in their care by promptly seeking veterinary evaluation of any masses.

Any mass, even those previously diagnosed as benign, warrants assessment if changes in size, shape, or color are observed, or if there is any indication of bleeding. Given the potential for cancerous or malignant masses to recur in the same area, it’s essential to closely monitor your dog for any new masses and promptly inform your veterinarian of any concerning developments.

Skin Cancer in Dogs FAQs

What are the characteristics of skin cancer in dogs?

Any abnormal mass appearing on or beneath your pet’s skin should be closely monitored. Changes in size, shape, texture, or the presence of bleeding should prompt immediate evaluation by a veterinarian. Additionally, any mass persisting for more than a month or exceeding the size of a pea warrants veterinary examination.

Can skin cancer be fatal for dogs?

Certain types of malignant skin tumors can indeed prove fatal if left untreated.

What is the life expectancy of dogs with skin cancer?

The life expectancy of a dog diagnosed with skin cancer largely hinges on the type of tumor present, underscoring the significance of early diagnostic testing. Prognosis for benign tumors is generally favorable and typically does not impact life expectancy. Malignant tumors, however, exhibit a wide range of effects on life expectancy. While some aggressive tumor types can significantly reduce a dog’s lifespan, others can be safely and effectively treated, preserving the dog’s longevity.

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