Skin Cancer in Cats
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What Is Skin Cancer in Cats?
Skin cancer is the abnormal growth of cells in the skin. Cancerous cells divide and grow without following the body’s instructions, which often leads to formation of a mass, or tumor. With skin cancer, there is usually an abnormality like a lump, bump, or oozing lesion. Skin cancer in cats is most often found on the head, neck, trunk, or legs.
A cancer can be benign, meaning it grows slowly and does not spread, or malignant, meaning it grows quickly and spreads. Malignant skin cancers can be very aggressive locally, meaning that they grow and spread rapidly in the region in which they are found. It is also possible for them to spread to other sites, such as the lymph nodes.
It is difficult to diagnose cancer based on appearance alone. To determine if a tumor is malignant or benign, cells must be taken and examined under the microscope. Testing can help give you more information regarding the type of cancer and expectations for what will happen next.
Types of Skin Cancer in Cats
While there are many different types of skin cancer in cats, the four most common are basal cell tumors, mast cell tumors, squamous cell carcinoma, and fibrosarcoma.
Basal cell tumors
Basal cell tumors occur in what’s called the basal layer of the skin. They lay on the bottom or base of the epidermis—the outermost layer. These tumors are usually firm and easy to grab and move around with your fingers. They are more common in senior cats, with Persians and Himalayans being more prone to this tumor type.
Basal cell tumors most commonly occur on the head, neck, and shoulders, but can be found anywhere on the body. They vary in size, are often hairless, and can be pigmented. Fortunately, basal cell tumors are benign and do not spread. Surgical removal is generally successful.
Mast cell tumors
Mast cell tumors most commonly occur on the head, neck, and legs, with over half of them occurring on the head. They are more common in middle-aged cats, with Siamese cats at a higher risk of developing this tumor type.
Mast cell tumors are often raised pink masses that are well-circumscribed so that you can move them around with your fingers. Cats can also have multiple mast cell tumors at once, and if that occurs there is associated with a poorer prognosis.
Squamous cell carcinoma
Squamous cell carcinomas may initially look like scabs or thickened skin, and often progress to oozing, bloody, ulcerated skin. This cancer type is more common on light-colored skin, with lesions more frequently occurring on the face, nose, and ears of white-faced cats. It is more prevalent in cats that spend a great deal of time outdoors, as sun exposure is linked to an increased risk of developing this type of cancer.
This tumor type may be itchy and lead to skin irritation. Many affected cats will want to scratch and rub the lesions. Squamous cell carcinoma is locally aggressive and can spread rapidly across the affected skin, making it difficult to remove all the cancerous tissue.
Fibrosarcomas are tumors of the connective tissue. Because there is connective tissue throughout the body, these tumors can be found anywhere. They are more likely in places where cats have had injections in the past, like vaccinations or other fluids and medications. The most common sites are between the shoulder blades and on the trunk near the hind legs.
A fibrosarcoma is typically a very firm mass that is well-connected to the underlying tissue. While most of these tumors are more locally aggressive, growing rapidly at their original site, about a quarter will metastasize or spread to other sites. The size and rate of growth are correlative with how dangerous the cancer is, with larger and more rapidly growing fibrosarcomas being associated with shorter survival times than slower-growing masses.
Surgery is recommended for treatment of this skin cancer type. However, many fibrosarcomas are difficult to remove.
Symptoms of Skin Cancer in Cats
Skin cancer can present in different ways depending on the type of cancer. The following are more common clinical signs of skin cancer in cats:
Lump or bump (raised area)
Ulcerated, bleeding, weeping, or oozing lesion
Pigmented or discolored region
Scabbing of the ears or nose
Red, flat plaque
Causes of Skin Cancer in Cats
Generally speaking, cancer is caused by a combination of genetics, environmental exposure, and chronic irritation or stimulation of the skin. The most common factors that increase a cat’s risk for developing skin cancer are:
Sun exposure—This is an especially heightened risk factor for light-furred or hairless cats, which have less natural protection from UV rays.
Genetics—Many breeds are predisposed to, or more likely to develop, certain types of cancer due to carrying linked genes. Persians and Himalayans are more prone to developing basal cell tumors, while Siamese cats are more likely to develop mast cell tumors.
Chronic skin irritation—Cats with underlying skin allergies or compulsive licking behaviors may develop chronic irritation and stimulation of their skin from licking, chewing, and scratching.
Physical trauma—Any physical trauma that disrupts the skin cells and leads to scar formation can increase a cat’s risk of developing skin cancer in the area.
How Veterinarians Diagnose Skin Cancer in Cats
If you suspect your cat may have skin cancer, make an appointment with your veterinarian. The exam will start with a close look at your cat’s skin, and the vet may decide to do a test called cytology, where cells are collected to be examined under a microscope. This may be done with a needle (most common in lumps and bumps) or by making an impression with a glass slide. Sometimes this is enough to confirm the type of cancer.
Certain tumors, like mast cell tumors, are recognizable under the microscope. But often, more information is needed to confirm a diagnosis. Your veterinarian is likely to recommend a biopsy, where a piece or all the abnormal tissue is removed and sent off to a laboratory for a veterinary pathologist to determine the disease process.
If metastases are suspected, your veterinarian may recommend x-rays or lymph node cytology to determine whether cancer has spread to distant sites.
Treatment of Skin Cancer in Cats
Most skin cancers in cats are managed surgically, with the tumor itself being removed. Your veterinarian will likely recommend sending the tissue off for histopathology, a process where abnormal tissue (skin or mass) is removed and sent to a lab. This allows the doctor to better determine what is causing the abnormal growth.
Sometimes surgery is not possible—when the tumor is too large to be removed, or when the patient is not a good candidate for anesthesia. For these patients, your veterinarian may recommend watchful waiting or a less invasive cancer treatment, including radiation and chemotherapy.
Recovery and Management of Skin Cancer in Cats
Recovery times vary depending on the type of skin cancer a cat is diagnosed with. Benign lesions, like basal cell tumors, are associated with a good prognosis. With these tumors, surgical removal is generally considered curative, and recovery is limited to 2 weeks following surgery for the incision to heal. Other cancers, like squamous cell carcinoma and fibrosarcoma, may have more prolonged treatment courses, with a decreased prognosis for complete recovery.
Pathology tests may give you more answers regarding survival times for the specific cancer type your cat was diagnosed with. If surgery is performed to manage skin cancer, expect to keep your cat calm and quiet for two weeks after, while the skin is healing. Keep the incision clean and dry and ensure your cat is unable to lick or chew at the incision site. Sometimes Elizabethan collars or recovery cones are required to keep your cat from licking or chewing on the incision.
Some tumor types, like mast cell tumors, may return later. It’s important to keep up with annual check-up appointments for your cat’s health and to note any new or returning tumors.
Prevention of Skin Cancer in Cats
Genetics plays a large role in whether a cat develops skin cancer, but there are some things you can do to decrease the risk. Limiting direct sun exposure when UV intensity is at its peak, especially in white-faced cats, can reduce the risk of developing squamous cell carcinoma.
There are commercially available sunscreen products safe for cats if limiting exposure is not possible. Cats that are hairless, like the Sphinx breed, or very light-colored, may benefit from this extra layer of protection.
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Villalobos, A. Merck Manual. Tumors of the skin in cats. October 2022.
Lawrence, J. Veterinary Specialists. Feline skin (cutaneous) squamous cell carcinoma. (2020)
Ho N, Smith K, Dobromylskyj M. National Library of Medicine. Retrospective study of more than 9000 cutaneous tumors in the UK: 2006-2013. 2017;20.
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