Squamous cell carcinoma (SCC) is a cancer that starts in the cells of the outer skin layer [6]. It is one of the skin cancers vets see most often in dogs, alongside mast cell tumors and melanoma [6], and sunlight is a known risk factor for it in both dogs and cats [1]. SCC can also grow in the mouth. This post covers the skin.
See your vet about a sore that does not heal, thick and discolored skin, or any problem with a toe or claw. Finding sun-damaged skin early, in the pets most at risk, is a key part of prevention [1].
For sun damage on cats’ ear tips, see solar dermatitis in cats. For other lumps on cats, see lumps and bumps on cats.
Sun and white skin
Ultraviolet (UV) light from the sun damages the DNA in skin cells, and over years this damage can turn cells cancerous [6]. Skin that is pale, thin-haired or hairless has the least natural protection [2].
Cats. In cats, most skin SCCs grow where there is little hair and little pigment [5]. The usual sun-exposed spots are a pale nose, the ear flaps and the eyelids [4]. In some sunny parts of the world, SCC is the tumor vets diagnose most often in cats [1].
Dogs. In dogs, SCC tends to grow on pale, thin-haired skin or in dogs with white coats, most often on the belly and flanks [2]. A large Australian study found Dalmatians, bulldogs, Staffordshire terriers and schnauzers at higher risk than mixed breeds [2]. Many pets enjoy lying in the sun even when shade is close by [1].
A warning stage. Sun damage can cause actinic keratosis (also called solar keratosis), a precancerous change [1]. It shows as red, inflamed skin with thick, scaly patches [1]. It sits on a spectrum of sun-related skin disease that can lead on to SCC [1].
Skin squamous cell carcinoma in dogs
- Who: dogs of any age can get it, but it mostly affects mature and older dogs [2], and white or white-patched coats are common among affected dogs [2].
- Where: mostly on sun-exposed, lightly pigmented or thin-haired skin, often the belly and flanks [2].
- Other factors: earlier sun damage to the skin and, in some dogs, a papillomavirus infection may play a part [2][4]. For warts in dogs and cats, see warts and papillomas.
Under the claw: subungual squamous cell carcinoma in dogs
SCC can also grow on a toe, under or around the claw. Sun is an unlikely cause there, and black-coated dogs are more often affected, so genes are thought to play a part [3]. Breeds with a known tendency include giant and standard schnauzers, black standard poodles, Rottweilers and black Labrador retrievers, with Briards and Beaucerons also overrepresented in one large study [3].
More than one toe can be affected, sometimes on different legs and sometimes months apart [3]. Toe SCC can spread to other parts of the body [3]. For other nail problems, see nail and nail bed problems.
Skin squamous cell carcinoma in cats
In cats, watch the ears, nose and eyelids, above all in white or pale-faced cats [4][5]. Early changes can look like a scab, a crusting sore or a red patch that does not heal. Any change in these areas should be checked by your vet.
Bowen disease. A related condition in cats is the Bowenoid in situ carcinoma, sometimes called feline Bowen disease or multicentric SCC in situ [4][5]. It is linked to papillomavirus infection [4][5]. The patches stay in the top layer of skin and often appear on haired, pigmented skin as crusting, roughly round spots that are darker or lighter than the skin around them [5]. Some fade by themselves, many persist, and some turn into invasive SCC, so they should be watched [5]. Devon Rex and Sphynx cats seem more prone, and in them the disease can be more aggressive [5].
How vets diagnose it
Your vet looks at the skin, toes and claws. A fine needle aspirate, where a thin needle collects cells from a lump, can give a quick first answer [6]. A biopsy, where a small piece of tissue is examined under a microscope, is the standard way to confirm the diagnosis and grade the tumor [6]. Only a sample can show what a growth is.
Treatment
Your vet will advise on treatment. Skin SCC that has not spread deeply is usually treated with surgery [6]. Other treatments are mainly kept for tumors that cannot be fully removed or that have grown into nearby tissue [6].
At home, as directed by a vet:
- check your pet’s skin, ears, nose, toes and claws, and tell your vet about any change;
- go back for every recheck.
Can it be prevented?
Pets at high risk are commonly advised to stay out of the sun at the times of day when UV is strongest [1]. Shade helps, but it does not protect a pet that chooses to sunbathe, and UV light passes through ordinary window glass [1]. Covering is hard for the nose and ear tips, the spots that are most exposed [1]. Ask your vet how to protect your pet.
Outlook
Outcomes vary between pets and tumors:
- Sun-linked SCC of the skin is slow to spread, but it can do real damage where it grows, often comes back, and new tumors can appear in other sun-damaged skin [1].
- SCC on the skin generally does better than SCC in the mouth or at the edges of the lips and other openings, which tends to be more invasive [6].
- SCC under the claw can spread, and new tumors can appear on other toes [3].
- In cats, Bowenoid in situ carcinoma stays in the top skin layer, but some cases progress to invasive SCC [5].
These are statements about groups of animals. They cannot predict how one pet will do. Your vet can explain what this means for your pet.
When to see your vet
Keep an eye on your pet’s skin, toes and claws, and have any problem checked by your vet promptly. See your vet if your dog or cat has:
- areas of thick, red or scaly skin [1];
- a small sore that does not heal;
- a raised, irregular lump, with or without open sores;
- crusting sores on the ears, nose, eyelids or lips of a white cat [4][5];
- lameness, a misshapen claw, an infected toe or a lost claw;
- crusting, darker or lighter round patches on a cat’s skin [5].
FAQ
Is a sore on my white cat’s ear tip cancer?
It can be sun damage or an early warning stage, or it can be squamous cell carcinoma. Sun damage can cause a precancerous change before a tumor forms [1]. Only your vet can tell, with a sample.
Which dogs are most at risk?
Older dogs and dogs with white coats or pale, thin-haired skin are at higher risk of skin SCC [2]. Black-coated breeds such as giant and standard schnauzers and black standard poodles are at higher risk of SCC under the claw [3].
Why does early diagnosis matter?
Sun-linked SCC often comes back and new tumors can appear in damaged skin [1], so spotting high-risk pets and early changes is key to prevention [1]. Skin SCC that has not spread deeply is usually treated with surgery [6].
The bottom line
Squamous cell carcinoma is a malignant skin tumor in dogs and cats. Years of sun on white, thin-haired skin is a major cause, on the ears, nose and eyelids of white cats and on the belly of some dogs. In dogs it can also grow under a claw. Thick, discolored skin, sores that do not heal and toe or claw problems need a vet check, because finding changes early gives your vet the most options.
This article is for general information only and does not replace advice from your veterinarian. If your pet has a sore that does not heal or a toe or claw problem, see your vet.
Sources
- Granados-Soler JL, Story MM, Allavena R, et al. Ultraviolet Light-Induced Skin Cancer and the Safety of Sunscreen Use in Pets: An Important but Under Researched Aspect of Companion Animal Health. Veterinary Sciences, 2026 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC13416697/
- Zhang JJ, Dejene H, Granados-Soler JL, et al. Demographic and environmental factors associated with canine cutaneous squamous cell carcinoma development in Australia: a retrospective matched case-control analysis. Veterinary Research Communications, 2026 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC13695678/
- Aupperle-Lellbach H, Heidrich D, Conrad D, et al. Comparative Study of Digital Squamous Cell Carcinoma in Giant, Standard, and Miniature Schnauzers. Animals, 2023 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC10295616/
- Munday JS, Knight CG. Papillomaviruses and Papillomaviral Disease in Dogs and Cats: A Comprehensive Review. Pathogens, 2024 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC11728566/
- Egberink H, Hartmann K, Mueller R, et al. Feline Papillomatosis. Viruses, 2025 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC11768494/
- Mârza SM, Munteanu C, Papuc I, et al. Comparative pathophysiology and molecular insights into cutaneous and non-cutaneous canine skin cancers: focus on melanoma, mast cell tumors, and squamous cell carcinoma. Frontiers in Immunology, 2025 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC12695799/