Lymphoma in Cats

What Is Lymphoma in Cats?

Lymphoma is a type of cancer that affects a cat’s lymphatic system. This system runs throughout the cat’s body and is composed of lymph nodes, ducts, spleen, bone marrow, thymus, and even parts of the gastrointestinal tract.

The lymph nodes are small, bean-like structures present throughout the body. Some of these nodes can be felt in a healthy cat under the jaw, on the neck, in front of the shoulder blades, and behind the knees.

This intricate lymphatic system is vital to maintaining a robust immune system. It transports nutrients throughout the body and eliminates harmful bacteria and viruses.

In cats, lymphoma is sometimes linked to other diseases, such as feline leukemia and feline immunodeficiency virus (FIV). Widespread vaccination has made lymphoma less common due to these conditions. However, lymphoma remains one of the most diagnosed cancers in cats today.

Types of Lymphoma in Cats

Lymphoma can occur in several areas of a cat’s body. Before widespread vaccination for feline leukemia virus, lymphoma tended to occur outside the GI tract. Today, intestinal lymphoma is most common, making up more than 50% of all lymphoma cases.

Typically, cats with lymphoma are older, usually 10 to 12 years old. Cats with intestinal lymphoma can have either a low-grade version, in which they experience thickening of their intestines, or a high-grade version in which large masses are formed in the intestines.

Other forms of lymphoma include:

• Mediastinal Lymphoma: Occurs when cats develop masses in their chest, either in the lymph nodes or the thymus gland. The mediastinum is the connective tissue holding the heart and lungs and soft tissue in the chest in place. Mediastinal lymphoma is more common in younger cats. Most of these cats are positive for feline leukemia virus. Siamese cats are more prone to developing this type of lymphoma.

• Renal Lymphoma: Occurs when lymphoma cancer develops in the kidneys. This type of lymphoma looks a lot like kidney disease, with symptoms including decreased appetite, vomiting, weight loss and an increase in drinking and urinating. Unfortunately, renal lymphoma often spreads to the nervous system, particularly the spinal cord and brain, and can be quite aggressive.

• Nasal Lymphoma: Occurs when cats develop a tumor in the nasal cavity.  This leads to frequent sneezing and nasal drainage. Sometimes, swelling can be seen on the bridge of the nose in advanced disease.

• Multicentric Lymphoma: This cancer is primarily in the lymph nodes of the body. Cats that develop multicentric lymphoma are often affected by either the feline leukemia or feline immunodeficiency virus. While this form is uncommon in cats, it is the most common form of lymphoma in dogs.

Symptoms of Lymphoma in Cats

The most common form of lymphoma is intestinal lymphoma. Cats with intestinal lymphoma will have gastrointestinal signs, such as:

• Vomiting

• Weight loss

• Diarrhea

• Lethargy

• Appetite changes

• A mass or firm growth in the abdomen

Other forms of lymphoma outside the GI tract have varying signs, depending on which system is affected. Cats with mediastinal lymphoma may struggle to breath and have trouble inflating their lungs due to the presence of a mass in their chest.

Cats with renal lymphoma often present with signs of kidney disease, like increased drinking and urinating, weight loss, and nausea.

Cats with multicentric lymphoma often have firm hard swellings under the chin, on the shoulder, and behind the knee, while nasal lymphoma symptoms can include sneezing or nasal drainage.

Causes of Lymphoma in Cat

Historically, lymphoma has been linked to infection with either the feline leukemia or feline immunodeficiency virus — especially with the mediastinal or multicentric forms of the disease.

Intestinal lymphoma does not seem to be connected to a viral infection. It is more likely due to a combination of genes and environment.

Other environmental factors, like secondhand smoke, have been linked to increasing a cat's risk for developing lymphoma. Cats living in a home where people smoke cigarettes are twice as likely to develop lymphoma.

How Veterinarians Diagnose Lymphoma in Cats

If lymphoma is suspected, your veterinarian will run several tests. First, they will likely run blood work, do a urinalysis, and take x-rays to look for signs of the disease. Specialty blood work may be recommended to check cobalamin (vitamin B12) levels. Low levels can indicate intestinal lymphoma. When intestinal lymphoma is suspected, an abdominal ultrasound is often done to look for widespread thickening of the intestines.

An intestinal biopsy, where tissue is taken for analysis, is the most effective diagnostic method. When a biopsy is performed, the pathologist will grade the lymphoma as either high-grade (more aggressive) or low-grade (less aggressive). This will provide more information regarding likely responses to treatment.

If the lymph nodes are involved, your veterinarian may recommend aspirating them to look at the cells. In this procedure, a needle is stuck into the swollen lymph node and cells are pushed on to a slide to look at under the microscope. Sometimes, advanced imaging such as computed tomography (CT) is recommended to get a better picture of masses under the surface of the skin, like the chest, kidneys, or nasal cavity.

Treatment of Lymphoma in Cats

Because the lymphatic system runs throughout the body, the disease needs to be treated with oral or injectable medications. The most effective way to do this is with chemotherapy.

In rare situations, cats may undergo surgery to remove the cancerous cells. It is usually performed to excise a nasal tumor or (even more rarely) a solitary abdominal mass. Most patients also will have chemotherapy. Radiation treatment is sometimes performed to shrink larger tumors, especially of the nasal cavity.

Sometimes chemotherapy is not an option, either due to lack of funds or to a pet parent’s preferences. In intestinal lymphoma patients, prednisolone (steroid) therapy alone can be helpful in managing the cancer and adding more quality of life.  Palliative care may be an option to keep your cat comfortable until the disease is no longer manageable.

Recovery and Management of Lymphoma in Cats

The prognosis for cats diagnosed with lymphoma varies depending on the type of lymphoma, when it was diagnosed, and if an underlying disease is present.

Intestinal lymphoma, the most common form of this cancer, tends to have the best outcomes. In cats treated with both prednisolone and chlorambucil, most cats’ lymphoma will go into remission.

While remission does not mean a cure, it does mean there are no longer any clinical signs of cancer. On average, it may be 2-3 years before signs of cancer return in low-grade intestinal lymphoma patients.

Cats treated with prednisolone alone may achieve remission. However, their remission time is much shorter, with the cancer coming back in 2-4 months.

Survival times are much shorter in high-grade intestinal lymphoma, and remission may never be achieved in cats that also have leukemia or FIV. Other sites of lymphoma, like mediastinal or renal lymphoma, are associated with much shorter survival times, often less than 3 months. Unfortunately, renal lymphoma commonly spreads to the brain and spinal cord, leading to rapid progression of the disease and loss of quality of life.

Prevention of Lymphoma in Cats

While there is no way to prevent lymphoma in cats, you can reduce your cat's risk of developing this cancer. Feline leukemia virus is linked to development of several forms of lymphoma. Regular vaccination for leukemia can keep your cat safe from the virus that increases their risk of developing lymphoma. 

If you smoke, avoid smoking in the house and exposing your cat to secondhand smoke, as it may double their risk of developing this cancer.