Basal Cell Tumors in Dogs

Basal cell tumors are one of the most common skin tumors found in dogs and they are almost always benign (non-cancerous). These growths can be mistaken for basal cell carcinomas, which are a malignant form of basal cell lesions affecting the epidermis or outer layer of skin. Basal cell tumors are usually harmless and present as firm, well-contained, hairless masses that can range from 0.2 to 10 centimeters in diameter (0.5 in – 4 inches). It is essential to get a veterinary diagnosis if you detect any mass or lesion on your dog. Together, you and your veterinarian will determine the right treatment plan going forward. Determining whether the tumor is malignant or benign will ensure that the appropriate treatment path is chosen.

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What Causes Basal Cell Tumors in Dogs?

The exact cause of basal cell tumors is unknown, but some factors may increase the risk of developing basal cell tumors including:

  • Age – Middle-aged to older dogs are more prone to benign skin tumors.
  • Genetics – Some dog breeds are predisposed to these tumors including Kerry Blue Terriers, Wirehaired Pointing Griffons, Poodles, Wheaten Terriers, Siberian Huskies, Cocker Spaniels, and Shelties.
  • Environmental – Sun exposure and chemicals may play a role in the development of these tumors.
    Whatever the cause of your dog’s tumor, the earlier it is diagnosed, the sooner treatment can begin, so be sure to take your dog to your local vet for a proper diagnosis.

Signs and Symptoms of Basal Cell Tumors in Dogs

The most notable sign of dogs with basal cell tumors is the presence of a raised, dome-shaped, hairless mass on the skin. These masses can appear anywhere, but they are most often seen on the dog’s upper body: the head (including ears), neck and shoulder region along the top of the back. Other signs of a basal cell tumor may include:

  • Itching, inflammation and/or pain at the site of the tumor
  • Bleeding from the tumor site
  • Ulceration of the skin at the tumor site
  • Lump with a stalk-like appearance
  • Darkened skin on the tumor
  • Draining fluid or pus from the tumor

How Are Basal Cell Tumors in Dogs Diagnosed and Staged?

Basal cell tumors can be diagnosed through either biopsy or cytology. During a cytological examination, a small sample of cells is taken from the tumor using fine needle aspiration (FNA) and examined under a microscope for diagnosis. If the cytology is unclear or non-diagnostic, then a biopsy will be taken for confirmation. A biopsy involves the surgical removal of a small tissue sample from the tumor which is then evaluated under a microscope by a veterinary pathologist. The biopsy will determine if the tumor is benign or cancerous. In about 90% of cases, these tumors are benign but confirmation is vitally necessary to determine if treatment is necessary.

How Does Basal Cell Tumor Progress?

Basal cell tumors can grow slowly over time if left untreated. And it is rare for them to become malignant. In fact, only 10% of these tumors are estimated to be cancerous. However, as these tumors grow, they on occasion can become painful for your dog and can be more difficult to remove surgically. Without treatment, your dog can develop symptoms that make these tumors uncomfortable for your dog including itching, bleeding, inflammation and ulceration.

Treatment Options for Dogs with Basal Cell Tumors

Treatment options for dogs with benign basal cell tumors depend on several factors including:

  • Tumor size
  • Location of the tumor
  • Stage or depth of the tumor

For the 90% of these tumors that are benign, the most common treatment options are either surgical removal or a watch-and-wait approach. Surgical excision or cryosurgery (freezing off the mass) are recommended if the lesion is growing, if the lesion is bothersome to the dog or for cosmetic reasons. If the lesion is small, stable and in no way causing any ill-effects for your canine, some people will take a watch-and-wait approach. It is important to so do only under the guidance of a veterinarian. Additionally, measurements of the mass should be taken and noted so that accurate reassessments can occur. As long as the basal cell tumor is in fact benign and is not causing any ill effects, it is fine to leave as is in many cases.

Should the mass change, grow or bother your pet, a prompt visit to your veterinarian is important. In the event the basal cell tumor is cancerous, it is considered basal cell carcinoma. If your dog has a cancerous skin tumor, a variety of treatment options may be employed including surgical removal, radiation therapy, chemotherapy and/or cryosurgery. Oftentimes, a combination of treatments is recommended for dogs with malignant skin tumors. A multi-pronged approach removes the cancerous lesion and prevents metastasis, which is when cancer cells spread to healthy tissues.

Prognosis for Dogs with Basal Cell Tumors

The prognosis for dogs with benign basal cell tumors is generally very good. When the tumor is discovered early and if it needs to be removed, dogs can go on living without further complications. If left untreated, while rare, these tumors can become uncomfortable for your dog so be sure to see a veterinarian promptly. If you’ve noticed a mass or tumor on your dog’s skin, feel free to reach out to our Pet Advocate Team at 833-738-4376. They are available to answer any questions you might have.

Has your dog been diagnosed with basal cell carcinoma? See the full article on treating basal cell carcinoma here.

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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