Cat skin cancer can look like a small sore that won’t heal, a firm lump under the skin, a scabby patch, or a dark-colored mass. The appearance varies depending on the type of cancer, but the most common visual clue is a skin change that persists, grows, or doesn’t respond to normal healing. Skin tumors in cats can also show up as hairless areas, discolored patches, or rashes, making them easy to mistake for minor injuries or skin irritation.
Squamous Cell Carcinoma: Scabby Sores That Won’t Heal
Squamous cell carcinoma (SCC) is one of the most recognizable skin cancers in cats, accounting for about 10% of all feline tumors. It’s driven by sun exposure, which is why it almost always appears on areas with thin or white fur: the nose, ear tips, and eyelids.
The earliest sign is often a small, reddened sore that looks like a scratch or scrape. Many owners assume their cat got into a scuffle. But the sore doesn’t heal. Over weeks, it develops into a scabby, crater-like lesion that keeps crusting over and reopening. On the ears, the skin along the edges thickens and starts to curl before becoming scabbed and eroded, gradually eating away at the ear tip. On the nose, lesions tend to sit right on the flat surface (the nasal planum) and look like a persistent raw spot.
As SCC progresses, the sores become raised, irregular lumps that may or may not have open ulcerations. White and light-colored cats are at the highest risk because they have less pigment to protect against UV damage.
Mast Cell Tumors: Firm Lumps on the Head and Neck
Mast cell tumors make up about 8% of feline tumors. On the skin, they typically appear as firm, flattened plaques or small nodules. They favor the head and neck, especially the top of the skull and the ears, though they can appear anywhere on the body.
A benign mast cell tumor is usually a single, hairless lump between 2 and 3 centimeters across (roughly the size of a marble to a grape). The more aggressive form tends to show up as multiple smaller lumps, each under 1 centimeter, sitting just beneath the skin surface. Because mast cells release substances that trigger inflammation, the surrounding skin may be red or itchy, and you might notice your cat scratching at the area more than usual.
Basal Cell Tumors: Dark, Round Masses
Basal cell tumors account for nearly 5% of feline tumors and are among the most common skin growths in cats. The good news is that most are benign.
They show up as firm, round, solitary lumps that can range from under 1 centimeter to over 10 centimeters across. In cats, about 25% of these tumors are black or dark gray, which can make them look alarming. Some stick out from the skin surface on a stalk-like base, almost like a mushroom. Others are cyst-like, filled with dark, pigmented fluid. The overlying skin is often hairless or ulcerated.
The malignant version, basal cell carcinoma, looks quite different. Instead of a raised lump, it appears as a flat ulcer on the head, legs, or neck. These ulcers spread outward and form new sores rather than growing upward from the skin. If you see a flat, expanding sore rather than a defined lump, that’s a more concerning sign.
Melanoma: Pigmented Spots or Masses
Melanoma is rare in cats, representing less than 1% of all feline tumors. These growths develop from the cells that produce skin pigment, so they’re most often black or very dark brown. They can appear as flat spots, raised patches, or distinct masses, primarily on the head or ears.
The tricky part is that not all melanomas are dark. A type called amelanotic melanoma produces little to no pigment, so it can be pink or skin-colored. Whether pigmented or not, the surface may or may not be ulcerated. Any new, persistent dark spot on your cat’s skin, especially on the face or ears, warrants a closer look.
Injection-Site Sarcomas: Lumps Between the Shoulders
Sarcomas are disproportionately common in cats compared to dogs, making up about 34% of all feline tumors. The vast majority of these (over 86%) are injection-site sarcomas, meaning they develop at locations where a cat previously received a vaccination or injection. Common sites include the area between the shoulder blades, the back of the hind legs, or along the flank.
These tumors typically feel like a firm lump beneath the skin. Most owners discover them while petting their cat. In the early stages, the lump may feel small and easily mistaken for scar tissue from a past injection. A useful guideline: have any lump evaluated if it has been present for more than three months, is larger than 2 centimeters (about the width of a nickel), or has grown noticeably over the past month. These sarcomas can grow rapidly, and larger tumors are more likely to be malignant.
Blood Vessel Tumors: Red or Bruise-Like Spots
Tumors that develop from blood vessels are less common but have a distinctive look. Benign versions (hemangiomas) appear as circular, compressible, red-to-black lumps that resemble blood blisters. You might be able to press one down slightly, since it’s essentially a collection of abnormal blood vessels.
The malignant form (angiosarcoma) is more aggressive. It usually shows up as one or more red lumps in the skin, or sometimes as a poorly defined area that looks like a bruise. These tumors grow fast, so a rapidly expanding reddish or purple patch on the skin is a red flag.
How to Tell Benign From Cancerous
There is no reliable way to determine whether a skin lump on your cat is benign or malignant just by looking at it. Visual appearance provides clues, but a definitive answer requires a biopsy or cell sample examined under a microscope. That said, certain patterns are worth knowing.
Growth speed matters. A lump that appears suddenly and gets bigger over weeks is more concerning than one that has stayed the same size for a year. Size also plays a role: larger tumors are statistically more likely to be malignant. Ulceration, meaning the surface breaks open and doesn’t heal, is another warning sign across nearly every type of skin cancer in cats. And location is important. Sores on the nose, ear tips, or eyelids in a light-colored cat point strongly toward squamous cell carcinoma. A lump between the shoulders in a vaccinated cat raises concern for an injection-site sarcoma.
Multiple lumps appearing at once can suggest either a benign condition or a more aggressive malignancy, depending on the type. Single, well-defined lumps are more often benign, while clusters of small, firm nodules beneath the skin surface lean toward the malignant end of the spectrum.
Which Cats Are Most at Risk
White and light-colored cats face the highest risk for sun-related skin cancers, particularly squamous cell carcinoma. Cats that spend time outdoors or like to sunbathe near windows are especially vulnerable on their ears, nose, and eyelids, where fur coverage is thinnest.
Any cat that has received vaccinations (which is essentially all domestic cats) carries some risk for injection-site sarcomas, though the overall incidence is still low. Older cats are more likely to develop skin tumors of all types. If you notice any new lump, sore, or skin change on your cat, particularly one that matches the patterns described above, having it checked promptly gives you the best chance of catching a problem early.