Basal Cell Tumors in Dogs

What Are Basal Cell Tumors in Dogs?

Basal cells are in the top layer of the skin, or epidermis. Basal cells make up the bottom layer of the epidermis and serve as a defensive mechanism, along with other types of cells.

Basal cell tumors are one of the most common skin tumors in dogs and are almost always benign, or non-cancerous. When basal cell tumors are malignant, or cancerous, they are called basal cell carcinomas. Basal cell carcinomas can sometimes be mistaken for benign basal cell tumors.

What Do Basal Cell Tumors in Dogs Look Like?

Basal cell tumors are most often found on a dog’s head, ears, neck, or front legs. These tumors are usually raised, dome-shaped, and firm, and can sometimes have a stalk, which allows them to stick out from the skin’s surface.

Benign tumors often have a stalk while malignant tumors do not. They are sometimes dark in color.

Basal cell tumors usually occur singularly and can be hairless and ulcerated.

Basal cell tumors vary in size from 1 to 10 centimeters in diameter. Although these tumors are benign, they can grow quite large, break open, and cause tissue death and draining infections.

Although skin tumors are not a medical emergency, all growths should be evaluated by your veterinarian as soon as possible.

Symptoms of Basal Cell Tumors in Dogs

Signs of a basal cell tumor include:

• Dome-shaped skin tumor on the head, neck, or shoulders

• Dark or skin-colored growth, with or without a stalk

• Itchy, inflamed skin at the tumor site

• Pain at the tumor site (also potentially manifesting as systemic signs, such as lethargy or decreased appetite)

• Ulceration and bleeding from the tumor

• Darkened skin around the tumor

• Pus or fluid draining from the skin growth

Causes of Basal Cell Tumors in Dogs

Basal cell tumors develop when basal cells or other skin cells, such as those from the sweat glands, hair follicles, or sebaceous glands, divide uncontrollably and cause an abnormal growth or mass.

While experts don’t understand exactly why skin tumors develop, some factors can increase a dog’s risk. Environmental effects, such as the sun, as well as genetics may play a role in the development of basal cell tumors in dogs.

Dog breeds that are predisposed to basal cell tumors include:

• Shelties

• Siberian Huskies

• Wirehaired Pointing Griffons

• Kerry Blue Terriers

• Wheaten Terriers

Basal cell tumors commonly occur in middle-aged and older dogs. Malignant basal cell carcinomas are more common in older Standard Poodles and Cocker Spaniels.

How Veterinarians Diagnose Basal Cell Tumors in Dogs

Basal cell tumors are diagnosed with cytology or a biopsy (i.e., histopathology). Fine needle aspiration (FNA), which involves collecting tumor cells for cytology using a needle and syringe, can be performed during a routine office visit without sedation.

The sample is then placed on a glass slide and examined under a microscope to identify the main cell type of the tumor, which can provide a diagnosis.

If your vet can’t get a diagnosis with cytology, or the tumor is large and needs to be surgically removed, a biopsy can be taken.

Biopsy involves surgically removing a small piece of the tumor and sending it to a veterinary pathologist for evaluation. A biopsy will determine the tumor type and whether the tumor is benign or malignant.

Biopsies require heavy sedation or general anesthesia, depending on the tumor’s extent and how long your vet thinks the procedure will take.

Prior to general anesthesia or sedation, your veterinarian will likely recommend pre-surgical blood work and chest X-rays to ensure your dog is healthy enough to undergo sedation or anesthesia.

Treatment of Basal Cell Tumors in Dogs

Treatment options for basal cell tumors depend on the size and location of the tumor.

Surgical removal as soon as possible is often the best course of treatment to prevent the tumor from rupturing and causing skin death and secondary infection.

If your dog has a secondary infection, they should receive oral medications (antibiotics) before and after the surgical procedure.

Although basal cell tumors grow slowly, larger tumors can be difficult to remove, especially if they are located on the head or leg, where there is little excess skin to close a surgical wound.

If the tumor is small and not bothersome, you can choose to monitor it for any progress that indicates the need for surgery.

Basal cell carcinomas should be surgically removed as soon as possible, regardless of their size and location, to prevent spread and other negative effects. In addition to surgery, malignant basal cell carcinoma treatment may include radiation and/or chemotherapy.

Specialty veterinary hospitals may offer cryosurgery, which uses low temperatures to freeze off the tumor.

Mass removal surgery includes removal of some normal tissue around the tumor as well. Once the tumor is removed (even if a biopsy was sent for evaluation before surgery) the entire mass should be sent to a veterinary pathologist. This is to ensure the entire tumor has been removed.

With complete excision, your dog is considered cured and their prognosis for a full recovery is excellent.

Recovery After Basal Cell Tumor Removal in Dogs

After surgery, your dog may have stitches or staples in their skin to close the incision. Your dog should wear a protective collar or cone collar after surgery to prevent them from harming the incision site, even if there are no visible stitches.

Pain and/or anti-inflammatory medications are often used after surgery to ensure your dog is comfortable during recovery. If a tumor is removed from your dog’s leg, your pup may require strict exercise restriction to prevent tension on the incision that could cause it to reopen or become infected.

It’s important to monitor the incision to ensure it doesn’t develop an infection. If you notice any redness, swelling, or discharge, or if the incision opens at any time, your dog should be evaluated by their veterinarian immediately.

Skin tumor removal typically requires a two-week recovery period, after which your dog will need a postoperative recheck by their vet to ensure they can return to normal activity.

Prevention of Basal Cell Tumors in Dogs

Since the cause of basal cell tumors is unknown, there is no way to prevent them from occurring.

If your pup is of a predisposed dog breed, monitor their skin for abnormalities and have any changes evaluated by your veterinarian as soon as possible.