Cancer in Cats: Types, Causes, and Treatment

A cat’s body is made up of millions of tiny cells that provide them with energy, contain DNA, and perform numerous functions, such as fighting infections.

Under normal circumstances, cells grow, divide, and die and are then replaced with new cells that repeat this cycle. Sometimes, cells become damaged but continue to grow and divide. This abnormal cell growth can lead to tumor development, which may be cancerous.

What Is Cancer in Cats?

Approximately 6 million cats in the United States are diagnosed with cancer each year, and 53 to 83% of tumors in cats are cancerous, or malignant. Survival of cancer in cats depends on the cancer type, whether it’s spread, and a cat’s overall health.

Types of Cancer in Cats

Cats can develop several types of cancer, including:

• Lymphoma—Lymphoma is the most common type of cancer in cats. This cancer affects white blood cells called lymphocytes which make up lymphoid tissue that is found throughout the body.  The GI tract, kidneys, and lymph nodes are commonly affected in cats.

• Mastocytoma—Mastocytomas, or mast cell tumors, develop from mast cells, which are made in the bone marrow and circulate throughout the body. Mastocytomas most often develop in the skin or spleen in cats.

• Leiomyosarcoma—Leiomyosarcoma is a rare but painful type of soft tissue cancer in cats that affects muscles in the stomach and intestines.

• Fibrosarcoma—Fibrosarcoma affects soft tissues such as muscle and connective tissue. It spreads slowly but can be locally aggressive.

• Mammary tumors—Mammary tumors affect the tissue surrounding a cat’s teat. They are aggressive tumors that generally spread to nearby lymph nodes and the lungs.

• Osteosarcoma—Osteosarcoma is bone cancer that affects the skeleton of cats. It is locally aggressive and painful.

• Ceruminous gland adenocarcinoma—Ceruminous gland adenocarcinoma develops in a cat’s sweat glands and often occurs in the ear canal.

• Melanoma—Melanomas are often isolated, raised masses that may bleed. They can affect many parts of the body, including the mouth, skin, and eyes.

• Myeloproliferative neoplasm—Myeloproliferative neoplasms are a type of blood cancer that originates from the bone marrow.

• Squamous cell carcinoma (SCC)—SCC is the most common skin tumor in cats and grows quickly.

• Hemangiosarcoma—Hemangiosarcoma is a fast-growing tumor that develops from blood vessel cells and may cause internal bleeding.

• Transitional cell carcinoma (TCC)—TCC is a tumor that grows in the bladder of cats. It is locally aggressive.

• Uterine cancer—Uterine tumors are rare in cats and typically affect middle aged and/or older cats. Treatment involves surgical removal of the uterus (ovariohysterectomy), commonly referred to as a spay.

• Ovarian tumors—Ovarian tumors are also uncommon in cats but are prone to metastasis (spreading). Often, the ovaries are a site of metastasis from other types of cancers. Treatment involves surgical removal of the ovaries, as in the case of a spay.

Symptoms of Cancer in Cats

Cancer in cats can cause several symptoms, which typically depend on the type of cancer. Symptoms may include:

• Visible lumps and bumps

• Lethargy

• Weight gain or loss

• Vomiting

• Difficulty eating

• Diarrhea

• Trouble breathing

• Difficulty passing urine or feces

• Bad breath

• Sores

• Bloating

• Blood in the feces

• Blood-tinged urine

Causes of Cancer in Cats

Many factors have been linked to cancer in cats, including:

• Toxins found in cigarette smoke and asbestos

• UV light

• Feline leukemia virus (FeLV)

• Feline immunodeficiency virus (FIV)

• Injections and vaccinations

• Healed fractures, device implantation, preexisting bone disease, and previous irradiation

• Age at time of spaying

• Breed, such as Siamese and Persian cats

• Age (varies according to type of cancer)

How Veterinarians Diagnose Cancer in Cats

Your veterinarian will start by reviewing your cat’s entire medical history. It can be helpful to track symptoms you observe prior to the appointment and take pictures of masses that are visible.

Next, your vet will perform a thorough exam and will likely test your cat’s blood and urine. They may also perform or recommend imaging tests, such as:

• X-rays—These may be taken to view your cat’s chest, abdomen, or limbs.

• Ultrasound—This provides real-time images of your cat’s internal organs.

• Endoscopy—This involves inserting a small camera into your cat’s mouth or rectum to view the stomach or intestines

• Computed tomography (CT)—CT uses a computer to make cross-sectional images of parts of a cat’s body with high resolution and contrast.

• Magnetic resonance imaging (MRI)—An MRI scan provides detailed images of your cat’s body without using radiation.

Imaging allows your veterinarian to see a tumor but does not diagnose the type of cancer your cat has.

Your vet may also collect a sample from the tumor to examine the cells inside it. A fine needle aspirate (FNA) involves inserting a needle into the tumor and using a syringe to suction cells that will be viewed under a microscope.

A biopsy involves surgically removing part of the tumor and viewing the cells under a microscope. Biopsies typically provide a more accurate diagnosis and can help your veterinarian predict how a tumor may act.

Cats that are not healthy enough for sedation or anesthesia may not be able to undergo more advanced tests, such as CT or MRI imaging, or a biopsy.

Treatment of Cancer in Cats

Whether or not your cat’s cancer is curable depends on many factors, including:

• Cancer type

• Pre-existing health conditions

• Cancer stage

• Tumor location and size

Your cat’s veterinary team will help determine the best treatment plan, which may involve:

• Surgery—Surgery is commonly performed to remove tumors located near the surface of the skin or that are localized to one area.

• Chemotherapy— Chemotherapy is given by injection or orally to kill cancer cells. It is often used for cancers that have already spread.

• Radiation—Radiation therapy uses targeted beams of radiation to kill cancer cells. It may be suggested for tumors that cannot be surgically removed.

• Immunotherapy—Immunotherapy uses your cat’s immune system to fight cancer, but it is relatively new in cats.

• Photodynamic therapy—Photodynamic therapy combines light and light-sensitive substances to destroy cancerous tissue.

A combination of treatments is often suggested for cats with cancer. For example, surgery to remove the tumor, followed by chemotherapy, can help ensure all cancerous cells have been removed or destroyed.

Some cats may not be healthy enough to withstand treatment, in which case palliative care may be used to keep them comfortable. Your cat’s veterinarian may prescribe pain and anti-inflammatory medications, a special diet, fluid therapy, and blood transfusions.

Recovery and Management of Cancer in Cats

Each cat’s post-treatment recovery and timeline varies. Your veterinarian will provide instructions and expectations for your cat’s individual needs.

There are several ways you can support your cat’s recovery:

• Keep them in a quiet enclosed space with fresh water, food, a bed, and litterbox nearby.

• Closely monitor your cat.

• Assist with your cat’s needs, such as grooming or eating.

• Follow guidelines given by your cat’s veterinarian.

• Prioritize follow-up appointments.

Many cats who are not candidates for treatment can still have a good quality of life. However, if a cat’s quality of life begins to decline, humane euthanasia may be recommended by the veterinarian. Your veterinarian can walk you through this option to ensure you and your cat are comfortable during the process.

Your veterinarian will help you decide what your cat may need during recovery. Below is a list of possible items:

• Oral syringes

• Waterproof blanket

• Pill pocket treats

• Cat bed

• Soft recovery cone

• Pet bathing wipes

Prevention of Cancer in Cats

Although many types of cancer can’t be prevented, there are some steps you can take to reduce your cat’s overall risk.

• Reduce your cat’s likelihood of contact with FeLV by keeping them indoors and keeping their vaccinations up to date.

• Reduce your cat’s exposure to indoor toxins, such as asbestos and tobacco smoke.

• Minimize your cat’s exposure to UV light.

• Prioritize annual vet appointments for young adults and biannual appointments for cats older than 8 years.