Something No One Wants to Talk About: Cat Cancer

No one wants to hear that their cat 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 bloodstream 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 pre-existing condition such as feline leukaemia virus (FeLV) or feline immunodeficiency virus (FIV) increases the risk of developing lymphoma. 

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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 in cats; it is a type of skin cancer and is the most common oral cancer in cats. It results from the malignant growth of epithelial cells: cells that 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 tumours are found during routine dental cleanings, so regular preventative dental care can help with early detection of cat skin cancer. Your cat’s vet 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 tumour 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 (FISS) are tumours that develop in the connective tissue at injection sites. While the exact reason these tumours develop is unknown, the present presumption is that inflammation at the injection site causes abnormal cell reproduction and tumour formation. 

Vaccines, long-acting antibiotics or steroid injections and microchips have been associated with this type of cancer. Tumours can develop anywhere from a couple of months to a decade after the actual injection. Despite this possibility, there’s no need to go against vaccines for fear of tumour 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 tumour is. Injection-site sarcomas are typically treated with a combination of surgery, radiation and chemotherapy. 

4. Mammary tumours

Mammary tumours 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 tumours 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 tumours 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 6–12 months of age) helps significantly decrease the likelihood of mammary tumours. 

Fine-needle aspiration or a biopsy are frequently used to diagnose mammary cancer. These tumours 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 carcinoma 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 tumours tend to occur in older cats, with Siamese and Persian being the most commonly affected breeds. These tumours tend to appear as a single, hairless, pigmented cyst or ulcer, typically on the head or neck. The good news is that basal cell tumours 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 tumour is malignant or if complete removal is not possible. 

Mast cell tumours 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 tumours are typically firm, raised and hairless and can show up as one single tumour or as a group. The area surrounding a mast cell tumour can become inflamed, especially if the cat is rubbing or scratching the area (these tend to be itchy). These tumours 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 tumours 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 vet 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 vet 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 vet or a veterinary oncologist can help you determine the best course of action for you and your kitty.