What Is Squamous Cell Carcinoma (SCC) in Dogs?
Squamous cell carcinoma (SCC) in dogs refers to the abnormal growth and uncontrolled proliferation of squamous cells, resulting in the formation of malignant tumors. Unlike benign tumors, which are non-cancerous, SCC tumors are cancerous and can spread to other parts of the body.
A dog’s skin comprises three primary layers: the subcutaneous layer (the deepest layer consisting of fat and connective tissue), the dermis (the second-deepest layer containing tissue, blood vessels, and sweat glands), and the epidermis (the outermost layer of the skin).
The epidermis contains three types of cells:
- Melanocytes: Found in the skin and eyes, melanocytes produce pigment called melanin and reside in the base layer of the skin.
- Basal cells: These cells generate new skin cells and constitute the middle layer of the skin.
- Squamous cells: Squamous cells are located in the outermost layer of the skin, closer to the surface.
SCC can develop anywhere squamous cells are present in dogs, including the:
- Mouth
- Paw pads
- Nose
- Abdomen
- Ears
- Nail beds
- Back
- Legs
- Scrotum
- Anus
It is typically classified as oral (affecting the mouth and nasal cavity), subungual (impacting nail beds and toes), or cutaneous (occurring in the skin).
What Does Squamous Cell Carcinoma (SCC) Look Like on a Dog?
Squamous cell carcinoma typically manifests as a solitary lesion or skin sore located somewhere on the dog’s body. However, multicentric squamous cell carcinoma, which involves multiple sores in more than one area, is extremely rare in dogs.
The appearance of squamous cell carcinoma sores can vary. They often present as small, red, and irritated-looking lesions. These sores may ulcerate, causing them to break open, or they may be covered by thickened patches of skin known as plaques.
The effects of these sores on a dog can vary depending on their location and severity. For instance, sores located on the toe or nail bed may lead to the loss of a dog’s nail. Additionally, sores that have ruptured and exposed the dog’s body to external germs may become infected, especially if the dog chews or licks the affected area.
Symptoms
The symptoms of squamous cell carcinoma in dogs encompass:
- Presence of small, inflamed sores on the body, which may appear red, covered in thickened skin, or bloody
- Observable behavior such as licking or chewing a specific area of the body
- Instances of missing toenails, blood evident on the floor, alterations in walking patterns, or reluctance to walk
- Excessive drooling, with or without the presence of blood
- Difficulties in swallowing or chewing
- Changes in walking patterns or a noticeable reluctance or inability to walk
- Weight loss
Causes
The development of squamous cell carcinoma in dogs is influenced by various factors, making cancer a multifaceted disease. The risk of your dog contracting squamous cell carcinoma depends on elements such as genetics, environment, and familial medical history.
Exposure to ultraviolet (UV) light stands out as a well-researched environmental risk factor. Additionally, squamous cell carcinoma can potentially arise due to canine papillomavirus, which is responsible for causing papillomas or warts in dogs.
Certain breeds are more predisposed to squamous cell carcinoma, including:
- American Pit Bull Terrier
- Basset Hound
- Beagle
- Bloodhound
- Boxer
- Bull Terrier
- Dalmatian
- German Shorthaired Pointer
- Golden Retriever
- Labrador Retriever
- Norwegian Elkhound
- Rottweiler
- Standard Poodle
- Whippet
Some breeds exhibit higher vulnerability due to factors such as lack of hair or light-colored fur or skin. The reasons for increased susceptibility in certain breeds remain unclear. For instance, despite having relatively dark toes, Rottweilers are more prone to developing squamous cell carcinoma in this area.
Older dogs are at a higher risk of being diagnosed with SCC compared to younger dogs. In a study involving 17 cases of squamous cell carcinoma, the age range of affected dogs varied from 2 to 14 years old. Gender does not seem to significantly influence the risk of squamous cell carcinoma, as the study showed a nearly equal distribution between males and females.
Diagnosis
To diagnose squamous cell carcinoma in your dog, the veterinarian needs to examine the squamous cells within the tumor. This examination typically involves either a fine needle aspiration (FNA) or a biopsy (the removal of a small piece of tissue).
During a fine needle aspiration, a small needle is inserted into the tumor to collect a sample of cells. This sample is then examined under a microscope for further analysis. On the other hand, a biopsy is a more extensive procedure, involving the extraction of a tissue sample from the tumor for detailed examination.
Depending on the results of these procedures, additional tests may be necessary for a comprehensive diagnosis.
Stages of Squamous Cell Carcinoma (SCC) in Dogs
Squamous cell carcinoma typically exhibits slow growth but has the potential to metastasize to local lymph nodes or the lungs if left untreated. Notably, cancer affecting the toes may progress more rapidly than in other areas of the body.
Your veterinarian may conduct tests to ascertain whether the squamous cell carcinoma has spread to other regions of your dog’s body, especially if it is present in the toes. This diagnostic process is referred to as staging.
Staging tests may involve radiographs (X-rays), ultrasounds, as well as analysis of your dog’s blood, urine, and lymph nodes. These assessments help determine the extent of the cancer and aid in developing an appropriate treatment plan.
Treatment
Surgery stands as the foremost recommended treatment option for squamous cell carcinoma. For small skin lesions near the surface of the skin that haven’t invaded nearby tissues, surgery can be relatively straightforward. However, larger tumors or those infiltrating nearby tissues may require more invasive surgical procedures. In such cases, your veterinarian might need to perform skin grafting to replace lost tissue from another area of the body.
Squamous cell carcinoma affecting the toes may necessitate the amputation of the affected digit. In advanced cases, amputation of the entire foot or leg may be advised. Squamous cell carcinoma impacting the jaw, especially when it invades the jawbone, may require the removal of part of the upper or lower jawbone through surgical procedures known as maxillectomy or mandibulectomy.
A combination of radiation therapy and surgery could be recommended to ensure the elimination of all diseased cells. Similarly, chemotherapy might be suggested alongside surgery to enhance treatment effectiveness. However, not all dogs may be suitable candidates for surgery due to health reasons or the inaccessibility of tumors. In such instances, radiation, medication, and chemotherapy may be the only viable options. Although they may not eradicate all cancer cells, these treatments can reduce tumor size and impede further growth.
For early detection of tumors, cryosurgery, involving the freezing and destruction of cancer cells using extreme cold, or photodynamic therapy, which employs drugs activated by light to eradicate cancer cells, may be employed.
To ensure your dog’s comfort, pain medication such as Carprofen/Rimadyl®, Gabapentin, and Tramadol may be prescribed. Additionally, your veterinarian may recommend antibiotics to prevent secondary infections.
Recovery and Management
Following surgery, your dog will require regular check-ups to monitor the cancer for any signs of recurrence. While recurrence is rare, dogs with multicentric squamous cell carcinoma may develop new sores after previous ones have been removed.
To prevent squamous cell carcinoma, it’s essential to limit your dog’s exposure to the sun. If you own a dog of any of the vulnerable breeds, it’s important to routinely inspect your dog’s skin, mouth, and toes for any abnormalities. Consider using a dog-friendly sunscreen, especially for dogs with white or light fur/skin, to provide additional protection against harmful UV rays.
Squamous Cell Carcinomas in Dogs FAQs
How common are squamous cell carcinomas in dogs?
Squamous cell carcinoma accounts for 5% of skin cancer cases in dogs and ranks as the second most prevalent form of oral cancer in dogs.
Can dogs have moles?
Dogs can develop moles anywhere on their body. While most are typically harmless, some may be cancerous and require evaluation by a veterinarian.
How long will a dog live with squamous cell carcinoma?
Survival rates with treatment vary widely depending on the location and stage of the tumor. Within the first year, dogs with squamous cell carcinoma can have survival rates ranging from 10% to 95%. However, dogs with metastasized squamous cell carcinoma in or on their toes typically have the shortest life expectancies.
