Cat Skin Cancer: Types, Signs, and Treatment

We all know the importance of sunscreen for preventing skin cancer in ourselves, but what about your feline friends? Can they get skin cancer? The short answer is yes, but it’s not always the same as we see in ourselves or in dogs. Find out what types of cat skin cancer are more common, what they look like, and what you can do about it.

Cat Skin Cancer: Prevalence and Types

Cancer in cats is significantly less common than in dogs, but that doesn’t mean it’s super rare. Unfortunately, an estimated 30 to 40 percent of all cats will get cancer. [1]

While lymphoma is the most common type of cancer in our feline friends, skin is the second most common site for tumor development — 30 percent of all tumors in cats occur in the skin. [2] [3]

Although skin tumors are less common in cats than in dogs, a tumor in a cat’s skin is more likely to be malignant than one on a dog. When we say “skin cancer,” we are specifically referring to malignant tumors of the skin. Unfortunately, it can be difficult to differentiate between benign and malignant skin tumors in cats, so any change to a cat’s skin warrants a check-up. 

The most common types of skin tumors in cats include:

• Basal cell tumors (less than 10 percent are malignant) [4]
• Squamous cell carcinoma (malignant)
• Mast cell tumors (malignant)
• Fibrosarcomas (malignant, including injection-site sarcomas)

When we think of skin cancer, a lot of us imagine melanoma as the big bad one. Melanoma is not a common skin cancer in cats, making up less than 3 percent of all skin tumors. Around 42-65 percent of melanomas in cats are malignant. [5]

In most cases, cats are diagnosed with skin cancer when they’re older, with the median age at diagnosis of cutaneous squamous cell carcinoma being 12 years old. [6]

The breeds with the highest incidence of skin cancer are Siamese and Persian cats. Cancers that can be caused by sun exposure, such as squamous cell carcinoma, are more common in lightly pigmented cats and less common in Siamese cats.

Stages of Skin Cancer in Cats

Various staging systems for cancers exist in cats. For skin cancers, such as squamous cell carcinoma, we can use a staging system known as the World Health Organization TNM classification system for feline tumors of epidermal (outer layer of skin) origin. You will typically hear reference to the specific T stages, which are as follows:

• T₀ = No evidence of tumor
• T_is = Tumor in situ, meaning abnormal cells are present but have not spread. These lesions are sometimes called pre-cancerous.
• T₁ = Tumor <2 cm diameter
• T₂ = Tumor 2-5 cm or minimally invasive
• T₃ = Tumor >5 cm or with invasion of subcutis (the bottom layer of skin tissue)
• T₄ = Tumor invading other structures such as fascia, muscle, or bone

The N stage is related to whether there is metastasis to lymph nodes while the M stage refers to whether there are distant metastases. Because a lot of skin cancers are locally invasive and don’t metastasize, for a lot of tumors, we refer primarily to the T stage.

Causes of Cat Skin Cancer

Skin cancer in cats is caused by a combination of genetic and environmental factors. 

Genetics: When specific breeds are prone to developing cancer, such as Siamese and Persian cats for skin tumors, we can assume that genetics play a role. 

Sun Exposure: Sun exposure can also lead to the development of skin tumors, particularly basal cell carcinoma and squamous cell carcinoma. These tumors are more common in lightly colored or hairless breeds because they have increased sun exposure. These tumors are also more common in cats who are outdoor only or indoor/outdoor in comparison to indoor only cats. Cats who spend a lot of time lying in windows and cats who live at higher altitudes may also be more likely to develop cancers related to sun exposure, as well as cats who live in countries with lower ozone coverage (such as New Zealand).

Mutations: The majority of mast cell tumors in cats show mutations that affect the replication and division of cells. In particular, one mutation in a specific proto-oncogene (a gene involved in normal cell growth) is observed in cats. However, not all mast cell tumors have this mutation, so we cannot assume this is the sole cause of mast cell tumor development in cats.

Vaccines: The relationship between vaccination and injection-site sarcomas (a type of fibrosarcoma) isn’t well-established. Currently, the theory is that genetically susceptible cats may develop this tumor in the site of a previous vaccination. In this scenario, it’s believed that the vaccination causes local inflammation, which results in cell proliferation, eventually causing tumor development. 

However, reports exist of these tumors developing at the sites of other injections, including medications, subcutaneous fluids, and possibly microchips. 

It’s not uncommon for cats to develop a small, firm lump where they received a vaccine in the weeks after getting their shots. This lump shouldn’t be getting larger 3-4 weeks after vaccination and should be gone within 3 months. An actual vaccine-associated sarcoma is rare, with an incidence somewhere between 1/1,000 and 0.63/10,000. [7]

Because infectious diseases pose a great risk to our cats while injection-site sarcomas are rare, the American Veterinary Medical Association emphasizes that this risk is not a reason to forego vaccination [2].

Skin Cancer Symptoms in Cats

Skin cancer in cats has a wide range of signs, so it’s important to get any change to your cat’s skin examined. 

Symptoms of skin cancer in cats may include:

• Solitary lumps in the skin, which can feel soft or firm
• Multiple nodules in the skin
• Loss of hair in the region of the tumor
• Sores that are crusty or scabby
• Wounds or ulcerated areas that may ooze clear fluid or blood
• Skin lesions with irregular borders
• Changes to skin pigmentation
• Red, bluish, or blackish plaques or nodules

Although a tumor can develop anywhere on a cat, these tumors do often have more common areas where they’re found.

• Basal cell carcinoma is often on the head, neck, shoulders, or chest.
• Squamous cell carcinoma commonly forms around the lips, nose, eyelids, and ear tips.
• Mast cell tumors commonly form on the head and neck but can be anywhere.
• Fibrosarcoma, especially injection-site sarcomas, are often on the limbs, tail, or between the shoulder blades in the areas of previous injections.

Sores, ulcerations, wounds, and hair loss in cats can have a wide range of causes which are more common than skin cancer, such as allergies, eosinophilic granuloma complex, bites from another animal, or ringworm. Most of these conditions will still require veterinary care, and some may be contagious to humans. Always get cat skin changes examined by a veterinarian.

Cat Skin Cancer Diagnosis

A cat skin cancer diagnosis will begin with a thorough examination. For most skin cancers, it will be impossible to differentiate a benign skin tumor from a malignant tumor without a biopsy. 

If there is a lump present, your veterinarian may stick a needle into the tumor to collect cells that can be examined under a microscope. This is called a fine needle aspirate or FNA. In some cases, such as a mast cell tumor, this can give a definitive diagnosis. In other cases, FNA can confirm the presence of a tumor but may not indicate if the tumor is cancerous (malignant) or benign or how aggressive the tumor is. 

In this scenario, or in cases where the lesion is more of a plaque or wound that cannot be aspirated, your veterinarian will recommend a biopsy. Biopsies must occur under sedation or anesthesia, depending on how extensive the procedure will be.

Staging may occur once a diagnosis is achieved. Your veterinarian will palpate the lymph nodes and may collect a sample from the lymph node with a needle. Staging can also involve X-rays of the chest or the area of the tumor, as well as abdominal ultrasonography. Advanced diagnostics, such as a CT scan or MRI, may be recommended to fully evaluate the extent of the tumor prior to treatment planning.

Cat Skin Cancer Treatment

For most cancers of the skin, the preferred treatment is radical excision of the tumor, meaning the tumor is removed surgically, along with a margin of normal skin around the tumor, and normal tissue deep to the tumor. 

In some cases where the cancer is located on your cat’s limb, amputation of the limb may be the best course of treatment. Luckily for our pets, they do very well as tripods! 

If the tumor is incompletely removed or has spread to other areas of the body, radiation therapy or chemotherapy may be recommended. Chemotherapy can be performed by the oncologist at a specialty center, but radiation therapy may require more extensive travel, such as to a university. Chemotherapy may include intravenous injections or direct injection into the tumor. 

Some veterinarians recommend cryotherapy for small lesions, in which the lesion is destroyed by freezing it. It should be noted that with this treatment, you will not know if the microscopic areas of the tumor have been successfully destroyed. Photodynamic therapy, in which the tumor is sensitized to light, is another treatment that may be performed at some specialty centers. 

The treatment options will depend on the type of tumor present and the extent of tumor invasion and spread.

In any case of cat skin cancer, long-term monitoring is recommended. For some tumors, such as fibrosarcomas, recurrence is common even with complete excision.

Cost to Treat Skin Cancer in Cats

Initial diagnostics and surgical removal of a tumor will likely add up to around $1,000-$2,000 for skin cancer in an easily excisable area if procedures are performed by your family veterinarian. 

However, this estimate rises significantly if the surgery is performed at a specialty center, if surgery is extensive or requires open wound management, and if chemotherapy or radiation therapy is needed. In this scenario, you’re looking at $5,000-$10,000.

If you are concerned about the cost of your cat’s cancer treatment, talk to your veterinarian or veterinary oncologist about payment plans or special financial assistance programs that may be available. Pet insurance can also help cover unexpected cancer-related costs. 

Cat Skin Cancer Prognosis

Prognosis for skin cancer will depend on the type of tumor, how large it is, whether it has spread, and the location on the body. 

For basal cell carcinomas and mast cell tumors, surgical excision is very often curative. Fibrosarcomas have a more guarded prognosis, with high risk of recurrence. If the fibrosarcoma develops in an area not amenable to surgery, such as between the shoulder blades, prognosis is poor. 

Location has a strong impact on the prognosis for squamous cell carcinoma, with ear tip squamous cell carcinoma being much easier to remove than carcinoma of the nose or eyelid. Some squamous cell carcinomas of the lip may be removable, but the tumor does often extend into the oral cavity. 

Generally, cats with skin cancer have a better prognosis if the tumor is caught early while it is small and more easily removed.

How to Prevent Skin Cancer in Cats

Not all cases of skin cancer in cats are preventable, but there are some steps you can take to reduce your cat’s risk.

If your pet is light-haired or hairless, consider limiting their sun exposure. This may include keeping them indoors or using clothing to prevent direct sunlight. 

It’s recommended to avoid smoking around your pet, as secondhand smoke may be linked to the development of cancers. 

When you take your pet in for vaccination, ask if your veterinarian can vaccinate low on the limb or on the tail. These areas allow for amputation in the rare event that a vaccine-associated sarcoma develops.

References

1. “Mammary Tumors.” Cornell Feline Health Center. Retrieved from: https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/mammary-tumors
2. van der Weyden L. “Spotlight on Feline Oncology.” Vet Sci. (2023 Mar);10(4):246. doi: 10.3390/vetsci10040246. PMID: 37104401; PMCID: PMC10141967.
3. Quintavalla F, Di Lecce R, Carlini D, Zanfabro M, Cantoni AM. “Multifocal Cutaneous Non-Epitheliotropic B-Cell Lymphoma in a Cat.” JFMS Open Rep. (2020 Dec);6(2):2055116920972077. doi: 10.1177/2055116920972077. PMID: 33414925; PMCID: PMC7750760.
4. Llera R, Stoewen D, Pinard C. “Basal Cell Tumors.” VCA Animal Hospitals. Retrieved from: https://vcahospitals.com/know-your-pet/skin-basal-cell-tumors#:~:text=Basal%20cell%20tumors%20are%20one,basal%20cell%20tumors%20are%20malignant.%22
5. Paul M. “Malignant Melanomas in Cats.” Pet Health Network. Retrieved from: https://www.pethealthnetwork.com/cat-health/cat-diseases-conditions-a-z/malignant-melanomas-cats#:~:text=In%20cats%2C%20melanomas%20are%20found,of%20those%20being%20malignant2.
6. Lana SE, Ogilvie GK, Withrow SJ, Straw RC, Rogers KS. “Feline Cutaneous Squamous Cell Carcinoma of the Nasal Planum and the Pinnae: 61 cases.” J Am Anim Hosp Assoc. (1997 Jul-Aug);33(4):329-32. doi: 10.5326/15473317-33-4-329. PMID: 9204469.
7. Saba CF. “Vaccine-Associated feline Sarcoma: Current Perspectives.” Vet Med (Auckl). (2017 Jan) 12;8:13-20. doi: 10.2147/VMRR.S116556. PMID: 30050850; PMCID: PMC6042530.