Lymphoma in Cats: Symptoms and Treatment

Lymphoma in cats is a cancer of the lymphatic system that can affect several areas of the body. Intestinal lymphoma is the most common form, but lymphoma can also affect the chest, kidneys, nasal cavity, and lymph nodes.

Treatment most commonly involves chemotherapy, while prognosis varies depending on the type of lymphoma, when it is diagnosed, and whether an underlying disease is present.

What Is Lymphoma in Cats?

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

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

The lymph nodes are small, bean-like structures found 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.

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. Today, intestinal lymphoma is the most common type, making up more than 50% of all lymphoma cases.

Before widespread vaccination for feline leukemia virus, lymphoma tended to occur outside the gastrointestinal (GI) tract. Cats with lymphoma are typically older, usually 10–12 years old.

Intestinal Lymphoma

Cats with intestinal lymphoma can have either a low-grade or high-grade form:

• Low-grade intestinal lymphoma: Causes thickening of the intestines.
• High-grade intestinal lymphoma: Causes large masses to form in the intestines.

Mediastinal Lymphoma

Mediastinal lymphoma occurs when cats develop masses in the chest, either in the lymph nodes or the thymus gland. The mediastinum is the connective tissue that holds the heart, lungs, and soft tissue in the chest in place.

This type of lymphoma is more common in younger cats. Most of these cats are positive for feline leukemia virus, and Siamese cats are more prone to developing this type of lymphoma.

Renal Lymphoma

Renal lymphoma occurs when lymphoma cancer develops in the kidneys. It can look a lot like kidney disease, with symptoms including decreased appetite, vomiting, weight loss, and increased drinking and urinating.

Renal lymphoma often spreads to the nervous system, particularly the spinal cord and brain, and can be quite aggressive.

Nasal Lymphoma

Nasal lymphoma occurs when cats develop a tumor in the nasal cavity. This can lead to frequent sneezing and nasal drainage.

In advanced disease, swelling may be seen on the bridge of the nose.

Multicentric Lymphoma

Multicentric lymphoma primarily affects the lymph nodes of the body. Cats that develop multicentric lymphoma are often affected by either feline leukemia virus or feline immunodeficiency virus.

While this form is uncommon in cats, it is the most common form of lymphoma in dogs.

What Are the Symptoms of Lymphoma in Cats?

Because intestinal lymphoma is the most common form of lymphoma in cats, common symptoms include vomiting, weight loss, diarrhea, lethargy, appetite changes, and a mass or firm growth in the abdomen.

Symptoms of Intestinal Lymphoma

• Vomiting
• Weight loss
• Diarrhea
• Lethargy
• Appetite changes
• A mass or firm growth in the abdomen

Other forms of lymphoma outside the gastrointestinal (GI) tract have different symptoms depending on which system is affected.

Symptoms of Mediastinal Lymphoma

Cats with mediastinal lymphoma may struggle to breathe and have trouble inflating their lungs due to the presence of a mass in their chest.

Symptoms of Renal Lymphoma

Cats with renal lymphoma often have signs of kidney disease, such as increased drinking and urinating, weight loss, and nausea.

Symptoms of Multicentric Lymphoma

Cats with multicentric lymphoma often have firm swellings under the chin, on the shoulder, and behind the knee.

Symptoms of Nasal Lymphoma

Symptoms of nasal lymphoma can include sneezing or nasal drainage.

What Causes Lymphoma in Cats?

The factors associated with lymphoma in cats can vary by type. Historically, lymphoma has been linked to infection with either feline leukemia virus or feline immunodeficiency virus, especially with mediastinal or multicentric lymphoma.

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

Environmental factors such as secondhand smoke have also been linked to an increased risk of lymphoma. Cats living in a home where people smoke cigarettes are twice as likely to develop lymphoma.

How Is Lymphoma in Cats Diagnosed?

Veterinarians may use blood work, urinalysis, X-rays, ultrasound, biopsy, lymph node aspiration, or computed tomography (CT) to diagnose lymphoma in cats, depending on where the cancer is suspected.

Initial Testing

If lymphoma is suspected, your veterinarian will likely start with blood work, a urinalysis, and 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.

Diagnosing Intestinal Lymphoma

When intestinal lymphoma is suspected, an abdominal ultrasound is often done to look for widespread thickening of the intestines.

An intestinal biopsy, in which 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 provides more information about likely responses to treatment.

Lymph Node Aspiration

If the lymph nodes are involved, your veterinarian may recommend aspirating them to examine the cells. During this procedure, a needle is inserted into the swollen lymph node, and cells are placed on a slide to be examined under a microscope.

Advanced Imaging

Sometimes, advanced imaging such as computed tomography (CT) is recommended to get a better picture of masses under the surface, such as those in the chest, kidneys, or nasal cavity.

How Is Lymphoma in Cats Treated?

Chemotherapy is the most effective way to treat lymphoma in cats. Because the lymphatic system runs throughout the body, the disease needs to be treated with oral or injectable medications.

In rare situations, cats may undergo surgery to remove cancerous cells. Surgery is usually performed to remove a nasal tumor or, even more rarely, a solitary abdominal mass. Most patients will also have chemotherapy.

Radiation treatment is sometimes performed to shrink larger tumors, especially tumors of the nasal cavity.

Sometimes chemotherapy is not an option, either because of lack of funds or a pet parent's preferences.

In cats with intestinal lymphoma, prednisolone (a steroid) therapy alone can help manage the cancer and add more quality of life.

Palliative care may be an option to keep your cat comfortable until the disease is no longer manageable.

Recovery and Prognosis of Lymphoma in Cats

The prognosis for cats diagnosed with lymphoma varies depending on the type of lymphoma, when it was diagnosed, and whether an underlying disease is present. Intestinal lymphoma, the most common form of this cancer, tends to have the best outcomes.

Low-Grade Intestinal Lymphoma

In cats treated with both prednisolone and chlorambucil, most cats' lymphoma will go into remission.

Remission does not mean a cure, but it does mean there are no longer any clinical signs of cancer. On average, it may be two to three years before signs of cancer return in cats with low-grade intestinal lymphoma.

Cats treated with prednisolone alone may achieve remission. However, their remission time is much shorter, with the cancer returning in two to three months.

High-Grade and Other Forms of Lymphoma

Survival times are much shorter in high-grade intestinal lymphoma, and remission may never be achieved in cats that also have feline leukemia or FIV.

Other forms of lymphoma, such as mediastinal or renal lymphoma, are associated with much shorter survival times, often less than three months.

Renal lymphoma commonly spreads to the brain and spinal cord, leading to rapid progression of the disease and loss of quality of life.

How To Prevent Lymphoma in Cats

There is no way to completely prevent lymphoma in cats, but you can take steps to reduce your cat's risk of developing this cancer.

• Protect your cat against feline leukemia virus. Feline leukemia virus is linked to the development of several forms of lymphoma. Regular vaccination for feline leukemia can help protect your cat from the virus that increases their risk of developing lymphoma.
• Avoid secondhand smoke. If you smoke, avoid smoking in the house and exposing your cat to secondhand smoke, as it may double their risk of developing lymphoma.