Squamous Cell Carcinoma
Squamous cell carcinoma
Also known as: SCC, Solar-induced squamous cell carcinoma, Multifocal squamous cell carcinoma in situ, Bowen's disease
Squamous cell carcinoma
Also known as: SCC, Solar-induced squamous cell carcinoma, Multifocal squamous cell carcinoma in situ, Bowen's disease
In short
Squamous cell carcinoma (SCC) is a common, sun-induced skin and oral cancer in dogs and cats, also occasionally affecting birds and turtles. Learn about symptoms, diagnosis, and treatment options.

TL;DR. Squamous cell carcinoma is a common, sun-linked skin and oral cancer in pets that requires early detection and aggressive treatment to manage successfully.

Older cats with white or lightly pigmented ears are highly susceptible to solar-induced squamous cell carcinoma.
Squamous cell carcinoma (SCC) is a malignant cancer originating from the squamous epithelium, which is composed of the flat, scale-like cells (keratinocytes) that make up the outer layer of the skin and line the moist tissues of the mouth. In pets, this cancer most commonly presents in two distinct ways: as destructive, non-healing sores on the skin (cutaneous SCC) or as highly aggressive, invasive tumors inside the mouth (oral SCC).
At a microscopic level, these cancer cells break through the delicate basement membrane that separates the outer skin layer from deeper tissues, invading local blood vessels, nerves, and surrounding bone. While cutaneous SCC tends to grow slowly and is less likely to spread to distant organs early on, oral SCC is highly invasive and destructive, rapidly eroding the jawbone and surrounding oral structures.
While this disease is most frequently diagnosed in dogs and cats, it can also affect exotic species, including birds and turtles. Because clinical research and large-scale studies in these exotic species are limited, much of our medical understanding and treatment protocols for birds and turtles are extrapolated from small animal medicine. Regardless of the species, early veterinary intervention is critical to achieving a favorable outcome.
The primary environmental trigger for cutaneous squamous cell carcinoma is chronic exposure to ultraviolet (UV) radiation from sunlight. Just as in humans, UV light damages the DNA within the skin cells, leading to mutations that cause uncontrolled cell division. Consequently, pets with white fur, light skin pigmentation, or sparse hair coats are at a significantly higher risk.
Geographic location also plays a major role; pets living in high-altitude regions or areas with intense, year-round sunlight experience much higher rates of solar-induced SCC. In cats, there is also evidence suggesting that viral infections may play a role in the development of these tumors. A leading veterinary surgery textbook notes:
"One paper suggests a papillomavirus may be involved in the etiology of feline squamous cell carcinoma. Older, white cats or those with lightly pigmented noses and that live in sunny climates are at risk. Lesions progress slowly through early solar damage with crusting and erythema to carcinoma in situ to invasive squamous cell carcinoma."
In dogs, sun-induced tumors are highly correlated with specific physical traits and lifestyle. According to a leading veterinary dermatology atlas:
"Sunlightinduced tumors on the flank and ventrum occur most commonly in lightly pigmented dog breeds such as Dalmatians, Beagles, Whippets, and White English Bull terriers. The condition is common in cats, with highest incidence reported in older white cats. The incidence of solar-induced squamous cell carcinoma is highest in geographic areas with intense sunlight."
The clinical signs of squamous cell carcinoma vary dramatically depending on where the tumor is located. Owners should regularly inspect their pet's skin, mouth, and paws for the following symptoms:

Solar-induced skin lesions on a dog's belly can progress from sun damage to invasive squamous cell carcinoma.
Your vet will begin with a thorough physical examination, paying close attention to any skin abnormalities, the oral cavity, and the lymph nodes. If a suspicious lesion is found, several diagnostic steps are required to confirm the disease and determine if it has spread.
While your vet may start with cytology (a fine needle aspirate to look at individual cells under a microscope), this test is not always definitive. As a standard veterinary cytology textbook explains:
"Because epulides are frequently composed of squamous epithelium and fibrous tissue, aspirates of these tumors are composed of variable numbers of mature squamous cells and occasional small spindle cells. The fibrous portion of the epulis is nonexfoliative or minimally exfoliative, and this causes many aspirates to be nondiagnostic because they consist entirely of blood or are almost acellular."
Because of these limitations, a biopsy with histopathologic examination is the gold standard for diagnosing squamous cell carcinoma. During a biopsy, your vet will remove a small piece of the tumor (or the entire mass) and send it to a veterinary pathologist. The pathologist will examine the tissue structure to confirm whether the cells are malignant and if they have invaded past the basement membrane.
Once SCC is confirmed, staging tests are performed to evaluate the extent of the disease:

Three-view chest X-rays are a critical staging test used to check if squamous cell carcinoma has spread to the lungs.
Treating squamous cell carcinoma requires a tailored approach based on the tumor's location, size, and whether it has spread.
For cutaneous and digital SCC, aggressive surgical removal is the treatment of choice. Your vet will aim for wide surgical margins to ensure no microscopic cancer cells are left behind. This may involve removing the tips of the ears (pinnectomy) in cats, or amputating the affected toe if the tumor is located in the nailbed. For oral tumors, surgery may involve removing a portion of the jawbone (mandibulectomy or maxillectomy).
If a tumor cannot be fully removed with surgery—such as those located on the face or inside the mouth—radiation therapy may be used. Combining radiation with hyperthermia (localized heat therapy) has shown promising results in shrinking tumors and controlling local disease. A leading veterinary internal medicine reference notes:
"Radiotherapy plus hyperthermia has been successful"
Systemic chemotherapy is generally less effective for SCC than it is for other veterinary cancers, but it can still play a role in management.
The prognosis for pets with squamous cell carcinoma is highly variable and depends heavily on the tumor's location.
Cutaneous (skin) SCC that is caught early and removed surgically carries a good to excellent prognosis. Many of these cases are slowly progressive, and local surgical removal can be curative, though owners must remain vigilant about sun protection to prevent new tumors from forming.
Conversely, oral SCC carries a guarded to poor prognosis, particularly in cats. These tumors are highly invasive, making complete surgical removal difficult. While treatment can improve quality of life and provide comfort, long-term survival times for oral SCC remain short.
For exotic species like birds and turtles, long-term prognosis data is limited due to a lack of published clinical trials. Treatment in these species relies on aggressive local therapy, and outcomes depend heavily on how early the disease is detected.
While you cannot change your pet's genetics, you can take active steps to prevent solar-induced cutaneous squamous cell carcinoma:
You should schedule a veterinary appointment if you notice any persistent redness, crusting, or non-healing sores on your pet's skin, ears, or nose.
Immediate veterinary attention is required if your pet exhibits severe bleeding from the mouth, sudden difficulty swallowing, rapid weight loss, or signs of extreme pain, such as vocalizing or refusing to walk on a swollen toe.
Certain breeds are genetically predisposed to developing squamous cell carcinoma, particularly those with light skin or sparse coats. Owners of the following breeds should practice strict sun safety and perform frequent skin checks:
Treatment must be prescribed by a licensed veterinarian based on your pet. Specific drug doses are intentionally not shown here.
Squamous cell carcinoma (SCC) is a common, sun-induced skin and oral cancer in dogs and cats, also occasionally affecting birds and turtles. Learn about symptoms, diagnosis, and treatment options.
Anorexia、Bleeding、Crusting、Dysphagia、Erythema、Halitosis、Proliferative skin lesions、Ulcerative skin lesions
Biopsy with histopathologic examination、CT scan、Cytology、Regional lymph node aspirate、Three-view thoracic radiographs
Treatment must be prescribed by a licensed veterinarian based on your pet. Specific drug doses are intentionally not shown here.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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