5 Common Types of Cat Cancer · The Wildest

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Now, Something No One Wants to Talk About: Cat Cancer

Veterinarian Dr. Alycia Washington breaks down the four most common types of cancer in cats, from how to spot the early signs to how to treat them.

by Dr. Alycia Washington, DVM, MS
Updated April 24, 2023
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No one wants to hear that their kitty could have cancer, which may bring up fears about your cat’s suffering, quality of life, and, yes, even death. We know, it’s truly the last thing you want to think about, but no matter your cat’s current stage of health, it’s important to stay informed for their (and your!) sake. Let’s chat about some of the most common cancers seen in cats and what to look out for.

1. Lymphoma

Lymphoma is one of the most frequently diagnosed cancers in cats. Lymphocytes are a type of white blood cell that help defend the body against infections. The bone marrow produces lymphocytes, which circulate throughout the body via the blood stream and lymphatic system. Lymphoma occurs when there is an abnormal increase of lymphocytes in the blood or in an organ and can occur in a variety of body systems. The most common location for this to take place is the gastrointestinal tract — other common locations include lymph nodes, the kidneys, and the nasal cavity. A preexisting infection with Feline Leukemia Virus (FeLV) or Feline Immunodeficiency Virus (FIV) increases the risk of developing lymphoma. 

The symptoms of lymphoma vary depending on the location of the disease and may include anorexia, weight loss, lethargy, GI upset, or breathing changes. A veterinary pathologist can diagnose lymphoma using microscopic evaluation of cells collected from abnormal lymph nodes, abnormal fluid drained from the chest or abdomen, or cells aspirated from other affected tissues. 

Chemotherapy is the most common treatment for lymphoma in cats. Your vet may also recommend radiation or surgery, depending on the type and location of the cancer. 

2. Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is another commonly diagnosed cancer; it is a type of cat skin cancer and is the most common oral cancer in cats. It results from the malignant growth of epithelial cells; these cells are found in the outermost layer of the skin and other organs. 

SCC most commonly appears on the nasal planum (the hairless part of the nose), on the tips of the ears, around the eyes, and inside the mouth. Cats with squamous cell carcinoma can develop lumps, non-healing sores, or ulceration in the affected area. White cats and cats who sunbathe excessively have an increased risk of developing SCC. Many times, oral tumors are found during routine dental cleanings, so regular preventative dental care can help with early detection of cat skin cancer. Your cat’s veterinarian can obtain cells from the lesion by aspirate or biopsy to definitively diagnose SCC.

Surgery is often the treatment of choice for squamous cell carcinoma. Although SCC is known to be an aggressive cancer, it is typically slow to progress. The goal of surgery is to remove the tumor entirely. If complete removal isn’t possible, partial removal combined with complementary treatments, such as radiation, cryotherapy, or laser therapy may be helpful. 

3. Injection Site Sarcoma

Feline injection site sarcomas are tumors that develop in the connective tissue at injection sites. While the exact reason these tumors develop is unknown, the present presumption is that inflammation at the injection site causes abnormal cell reproduction and tumor formation. 

Vaccines, injections of long-acting antibiotics or steroids, and microchips have been associated with this type of cancer. Tumors can develop anywhere from a couple of months to a decade after the actual injection. Despite this possibility, there’s no need to go all anti-vax for fear of tumor development. The risk is low — far lower than the risk of your cat dying from preventable diseases because they are unvaccinated. 

Cats with injection-site sarcomas develop firm masses under the skin. These masses are typically not painful. Injection-site sarcomas are often diagnosed with a biopsy. Advanced imaging like a CT scan or an MRI may be recommended to determine how deep or widespread the tumor is. Injection site sarcomas are typically treated with a combination of surgery, radiation, and chemotherapy. 

4. Mammary Tumors

Mammary tumors are also commonly diagnosed in cats. While mammary masses can be benign or malignant, most in cats are malignant and will spread to the lymph node or lungs prior to detection.

Symptoms seen with mammary tumors include swelling of the affected mammary gland, ulceration or redness of the skin of the belly, or discharge from the affected nipples. Naturally, female cats are at higher risk of developing mammary tumors than male cats. While there’s no need to start performing monthly breast exams on your feline, new lumps or changes to the appearance of the mammary glands should be checked out. Spaying early in life (before six to 12 months of age) helps significantly decrease the likelihood of mammary tumors. 

Fine-needle aspirate or biopsy are frequently used to diagnose mammary cancer. These tumors can be treated with a combination of surgery, chemotherapy, and radiation. 

5. Skin Cancer

Cats can develop multiple types of skin cancer, and their fur can either highlight or camouflage skin changes. Although not every lump or bump is harmful, you should not ignore skin changes.

A basal cell tumor is a cancer that affects the top layer of skin, hair follicles, and sebaceous glands and is the most common form of skin cancer in cats. Basal cell tumors tend to occur in older cats, with Siamese and Persian being the most common breeds affected. These tumors tend to appear as a single, hairless, pigmented cyst or ulcer, typically on the head or neck. The good news is that basal cell tumors are usually benign and rarely spread to the lymph nodes. Your vet will likely opt for surgical removal. Radiation and/or chemotherapy may be pursued if the tumor is malignant or if complete removal is not possible. 

Mast cell tumors are the second most common skin cancer in cats. Mast cells are part of the immune system and release histamine and other substances when triggered. Mast cell tumors are typically firm, raised, and hairless and can show up as one single tumor or as a group. The area surrounding a mast cell tumor can become inflamed, especially if the cat is rubbing or scratching the area (these tend to be itchy). These tumors are usually benign, but can spread to the lymph nodes and other organs. Complete surgical removal is the treatment of choice, but medical management is an option if surgery cannot be performed.  

Cats can also develop melanoma, a cancer of the melanin-producing cells in the skin. Unlike in people, exposure to sunlight doesn’t have anything to do with melanoma development in cats. Cats get melanoma far less often than dogs, but malignant melanoma is more common in cats. Melanoma can develop in the mouth or the eye (this is bad news and aggressive). Melanoma tumors usually occur on the face or head but can pop up on other parts of the body. Once again, the recommended treatment is complete surgical removal. Radiation is recommended when wide surgical margins can’t be achieved. 

What happens when your veterinarian says your cat might have cancer?

First, a vet will perform a biopsy or fine-needle aspiration of the mass to confirm the diagnosis. Next, staging determines if the cancer has spread anywhere else in the body. Radiographs, ultrasound, and lymph node aspirates are common tools for staging. Then, your veterinarian will discuss treatment options based on the cancer type, stage, and grade.

While nobody wants to hear that their feline friend may have the Big C, working together with your family veterinarian or a veterinary oncologist can help you determine the best course of action for you and your kitty.

alycia washington, dvm

Dr. Alycia Washington, DVM, MS

Alycia Washington, DVM, is a small animal emergency veterinarian based in North Carolina. She works as a relief veterinarian and provides services to numerous emergency and specialty hospitals. Dr. Washington is also a children’s book author and freelance writer with a focus on veterinary medicine. She has a special fondness for turtles, honey bees, and penguins — none of which she treats. In her free time, Dr. Washington enjoys travel, good food, and good enough coffee. 

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