Cancer in Cats: Symptoms, Types and Treatment

Reviewed for accuracy on August 26, 2019, by Dr. Katie Grzyb, DVM

Early veterinary intervention with cancer cases is critical. Although catching it early doesn’t always lead to a good prognosis, early diagnosis helps you and your veterinarian give your cat the best quality of life for the longest time possible.

Understanding the different types of cancer in cats and learning to spot the symptoms is an essential part of being a proactive pet parent.

Here’s a rundown of the feline cancers that are seen the most often.

Lymphoma: The Most Common Type of Feline Cancer

Lymphoma is by and large the most common cancer that affects cats, although there are other types of feline cancers that can affect domestic cats.

Lymphoma typically happens in older felines and most commonly occurs in the small intestines, says Dr. Theresa Arteaga, DVM, DACVIUM (Oncology), owner of Animal Cancer Center in Monterey, California.

Symptoms of Feline Lymphoma Cancer

According to Dr. Arteaga, these are the symptoms of lymphoma in cats:

• Weight loss (primary symptom)

• Vomiting

• Anorexia (not eating)

• Diarrhea

Risk Factors

Possible factors that contribute to the likelihood of a cat developing lymphoma include:

• Being positive for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV)

• Exposure to secondhand smoke

• Diet

• Genetics (Siamese cats are overrepresented)

Treatment

It’s usually a highly aggressive form of cancer, but is treatable with chemotherapy, says Dr. Joshua Lachowicz, DVM, DACVIM (Oncology), medical director at BluePearl Pet Hospital in Queens, New York. “Remissions are achieved in approximately 60-80% of cats.

This is seen in cases that follow the gold standard of chemotherapy—the longest protocol and most expensive. But many cats go out of remission and still have a great quality of life for years, during and after chemotherapy.

Soft-Tissue Sarcomas

The term “soft-tissue sarcoma” encompasses a broad category of tumors that show up in a cat’s connective, muscle or nervous tissues.  

Soft-tissue sarcomas include:

• Fibrosarcoma

• Leiomyosarcoma

• Liposarcoma

• Nerve sheath tumor (previously called neurofibrosarcoma, schwannoma, hemangiopericytoma)

• Rhabdomyosarcoma

• Vaccine-associated sarcoma

• Undifferentiated sarcoma

Most commonly, these tumors are found over the chest, back, side, legs and facial tissues of pets.

Symptoms of Feline Soft-Tissue Sarcomas

The symptoms of a soft-tissue sarcoma depend on its location on a cat; however, the predominant symptoms are:

• A mass that you can feel

• Lameness

• Vomiting

• Having difficulty urinating

Treatment

Dr. Lachowicz explains that soft-tissue sarcomas “may be less aggressive, with progression occurring over weeks to months. If metastasis has not occurred, treatment with surgery and radiation therapy is highly successful.”

Squamous Cell Carcinoma

Squamous cell carcinomas are malignant tumors that are locally invasive. They can occur in various areas, but they most commonly show up in the mouth, says Dr. Lachowicz.

These tumors grow very quickly, so early detection is key.

Dr. Lachowicz explains, “These are very difficult to treat unless detected and removed early, so oral care by a vet is highly important.” He recommends taking your cat for vet exams every six months when they are eight to 10 years of age.

Symptoms of Squamous Cell Carcinomas in Cats

According to Dr. Lachowicz, symptoms of squamous cell carcinomas may include:

• Difficulty eating

• Discomfort

• Halitosis

• Weight loss

• Drooling or salivating excessively

• Swelling of the upper or lower jaw

• Bleeding from the mouth

Treatment

Once a tumor is confirmed to be a squamous cell carcinoma through a biopsy, there are a few treatment options. During the early stages, the tumor can be removed surgically or treated with radiation.

In the more advanced stages, the treatment options become very limited. Radiation is the predominant choice, but there is no guarantee that it will successfully control the tumor.

Mammary Carcinoma

Feline mammary carcinomas represent the third most common type of feline cancer overall and the most frequently diagnosed feline cancer in cats older than 10 years of age.

Cats have two “chains” or rows of mammary glands with four in each chain. They run the length of a cat’s belly, which means that tumors can develop anywhere from the armpit to the groin, says Dr. Lachowicz.

These tumors may originate in the mammary gland, but they can metastasize to the lymph nodes, adrenal gland, lungs, liver pleura and kidneys.

Symptoms of Feline Mammary Carcinomas

Symptoms of a mammary carcinoma include:

• One or more palpable masses underneath the skin in the stomach area

• Affected area will feel warm to the touch or could be painful in some cases

Risk Factors

“There is a higher risk of developing these tumors in cats spayed after one year of age,” says Dr. Lachowicz.  

Siamese cats have also been found to be at twice the risk for this type of cancer than other breeds, but the reason for this is still unknown.

Treatment

Treatment of a mammary tumor will depend on whether the tumor has metastasized or not. If the tumor has spread to other parts of the body, the treatment would primarily be chemotherapy.

If caught early, and the tumor is still confined to the mammary glands, a mastectomy (removal of one or both chains of mammary glands and underlying tissues) can be performed.

General Symptoms of Cancer in Cats

Symptoms vary by patient and type of cancer, and they can occur at varying paces in cats.

“They may be gradual and progress over weeks to months, or more acute and rapid. Any new or ongoing changes should be evaluated by the vet accordingly,” says Dr. Lachowicz.

Also look for gastrointestinal symptoms: “Pay attention to what is in the litter box, for changes in the consistency, color and odor of feces, as well as urine output,” says Dr. Arteaga.

Keep in mind that these symptoms don’t necessarily indicate cancer. Only your veterinarian can make a proper diagnosis.

Diagnosing Cancer in Cats

Veterinarians rely on many of the same diagnostic tools used in human medicine, including blood work, radiographs, ultrasounds, MRIs, cat scans and pet scans.

“Cells can be obtained by aspirating a mass or tumor with a needle—or evaluating whole blood in the case of leukemia—and analyzed by cytology, which is a microscopic cell analysis,” says Dr. Lachowicz.

Aspiration can be performed on masses that are at the skin level, under the skin (subcutaneous) or in internal organs, as long as the mass is easy to reach with a long needle. Usually these aspirations are performed with an abdominal ultrasound by a trained veterinarian to avoid internal injury.

Alternatively, or in addition to cytology, a tissue sample may be obtained surgically for histopathology (biopsy),” says Dr. Lachowicz.

Biopsy usually requires sedation and requires a much larger tissue sample for evaluation. 

General Treatments for Cancer in Cats

Cats usually lag behind dogs for new cancer treatment protocols. Still, “with what’s available to us, we have good options, and depending on the cancer, it’s well tolerated,” says Dr. Lachowicz.

Some forms of malignant feline cancer, for example, can be cured with surgery—with or without the use of radiation therapy. Others, such as lymphoma, can be successfully treated with chemotherapy, he says.

“Cats tend to do very well with treatment across the board. They recover nicely from surgery if it’s a surgical case. With radiation, the side effects in cats are much less severe in most cases. In chemotherapy they have mild side effects—90% of the time, they’re going to have minimal-to-no side effects, and in the cases that they do have side effects, they’re going to be mild. The ones that are going to be moderate are less than 10%,” says Dr. Lachowicz.  

Managing Feline Cancer

“Our focus in veterinary oncology is always quality of life, first and foremost, rather than whether we can extend the animal’s life. So we’re very conscience of that,” says Dr. Lachowicz.

With that in mind, a major challenge is medicating a cat at home. “There are several chronic diseases that will call for long-term oral medications, and this can be challenging. So much time is spent on making this feasible, ranging from compounded medications in tasty flavors to more concentrated doses so the amount is less,” says Dr. Arteaga.

Finding a veterinary oncology team that’s comfortable with cats is important, she says. “A lot of thought has to be put into de-stressing in the hospital, [trying] to stay on an outpatient schedule, [offering] quiet calm rooms and lots of tasty treats, and [giving] owners realistic goals.”

Reducing Feline Cancer Risks

It’s essential to incorporate practices that help reduce the risks of feline cancer; for example, a good diet, exercise, low stress and avoidance of secondhand smoke, says Dr. Arteaga. Also, “Be diligent about yearly vet appointments and biannual exams when a cat is older, as often, the disease will be caught earlier.”

Always err on the side of safety and run past any new symptoms with your veterinarian. Early intervention is often key to effectively treating cancer in cats and improving their quality of life.

By Paula Fitzsimmons

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