What causes lymphoma in cats

Lymphoma is one of the most common cancers diagnosed in cats. It is a cancer of the lymphocytes (a type of white blood cell) and is found throughout many areas of the body which include: lymph nodes, spleen, liver, gastrointestinal tract and bone marrow.

Unlike lymphoma in dogs, viral causes of feline lymphoma are well defined, and the feline leukemia virus (FeLV) has been shown to cause a significant (~60 fold) increase in risk for development of lymphoma in cats. We typically see lymphoma diagnosed in younger cats that are infected with the feline leukemia virus, and in older cats that are not infected with the virus. Other possible risk factors include exposure to second hand tobacco smoke, chronic immunosuppressive therapy, as well as chronic inflammatory diseases.

Types of Lymphoma

Lymphoma can be subdivided into several different forms which is dependent on location of the tumor. These locations can include:

Gastrointestinal Tract: The most common form is involvement of the gastrointestinal (GI) tract. This includes the stomach, intestines and liver; as well as some of the lymph nodes surrounding the intestines. Cats with this type of lymphoma often have clinical signs consisting of vomiting, diarrhea, weight loss or a decreased appetite.

Mediastinal: The mediastinum is a term used for a special aggregation of lymphoid tissue in the chest. Cats with this type of lymphoma are usually young and often seen because of a sudden onsent of difficulty breathing, decreased energy level and decrease in appetite.

Renal: The kidneys can be the primary sites of involvement. Cats that have this type are often seen because of signs related to kidney failure (increased thirst, increased urination, loss of appetite, vomiting).

Bone Marrow: If the cancer were confined to the bone marrow, it is considered leukemia. Most patients are presented to the hospital for a decrease in energy and appetite. Bloodwork, usually reveals a change in their red blood cell and white blood cell counts.

External Lymph Nodes: In a few cats, the only site of involvement is the external lymph nodes. These cats may be seen because of problems such as vomiting and loss of appetite or because the owner found “lumps” (enlarged lymph nodes) on their cat.

Other Sites: We will occasionally see other sites such as the skin, nose, brain and spinal cord as the primary site of involvement

Diagnosis and Initial Evaluation

A biopsy (tissue) or cytology (aspirate) sample is required in order to make a diagnosis of lymphoma. In some cases, we can obtain a diagnosis by a fine needle aspirate, but in other situations, a biopsy to obtain a larger piece of tissue is necessary to confirm the diagnosis. The ease with which a diagnosis can be obtained depends upon where the tumor is located.

The first step for any patient suspected of having lymphoma includes determining the extent of the disease which is known as staging. This includes a complete blood count (CBC), serum chemistry profile (which looks at things such as liver and kidney function, protein levels, blood sugar and electrolytes), urinalysis and FeLV/FIV testing are always recommended and provide important information regarding the effects of the cancer on body functions as well as the ability of the patient to handle chemotherapy or other treatments. Additional tests include chest radiographs, abdominal ultrasound along with possible bone marrow aspirate and CT/MRI. Once we determine the extent of disease, we can then decide on the best treatment for your pet.

Treatment and Prognosis

Chemotherapy is the mainstay of treatment for lymphoma; however, there may be situations when surgery and/or radiation are also indicated. Radiation therapy may be recommended if the cancer is localized to one site such as the nasal cavity. Specific recommendations will be discussed based on your pet’s particular situation.

Fortunately, lymphoma is very responsive to chemotherapy where 50-70% of treated cats will go into remission. The definition of remission is the complete disappearance of detectable cancer; however, microscopic amounts of tumor cells can remain hidden in the body. A remission is NOT a cure but it does allow your pet to experience a good quality of life without clinical signs associated with their disease. The length of the remission depends upon many factors including the primary site, how your pet is at the time of diagnosis and the extent of disease. In most situations, the median remission and survival times (with chemotherapy) are between six to twelve months; with 25% of cats experiencing disease control for greater than one year and approximately 10-15% of cats living longer than two years.

Solitary lymphoma such as nasal is generally treated with radiation +/-chemotherapy. The radiation can be considered definitive with the intent for long term control or palliative for symptom relief in order to
Improve and/or maintain the patient’s quality with minimal negative impact. The prognosis for solitary lymphoma such as nasal lymphoma is generally better with many cats achieving local control for 1-1.5 years although there is still a concern that the cancer may spread within 3-6 months. If solitary lymphoma is treated with radiation and the cancer progresses down the road, then chemotherapy can be considered at that time.

The exact chemotherapeutic drugs and schedule will depend upon how aggressively the cancer is behaving, how sick your pet is at the start of treatment, any abnormalities in organ function (particularly kidneys and liver), and the goals of treatment. Chemotherapy is most effective when we used a combination protocol; therefore, most protocols generally consist of 4-6 different drugs. This is called a multi-drug protocol. Multi-drug protocols most commonly include Elpsar (L’asparaginase), Vincristine (Oncovin), Cytoxan (Cyclophsophamide), Adriamycin (Doxorubicin) and Prednisone. Initially, treatments are given more frequently (i.e. once weekly) and then, depending upon the response and protocol used, are gradually spread out and/or discontinued. Other options for therapy may consist of using a single chemotherapy drug (single agent therapy) at 3- week intervals, or palliative care which is simply designed to keep your pet comfortable at home for as long as possible. Bloodwork and/or X-rays/ultrasounds are generally repeated at regular specified intervals to monitor for side effects (such as a low white blood cell count) and to determine the your pet’s response to treatment.

Side effects

Fortunately, most cats tolerate chemotherapy very well and experience minimal side effects. Serious side effects are only seen in 5% of the patients which require outpatient care and less than 1% will require hospitalization or experience any life threatening side effects. If side effects are serious or intolerable, we can consider either lowering the dose of the offending drug or substituting a different drug. Side effects include nausea, vomiting and loss of appetite, diarrhea, extreme tiredness or rarely infection. Certain chemotherapy agents can affect organ function over time, so close monitoring with bloodwork is recommended. Cats do not lose their hair but may lose their whiskers and have a different texture to their fur secondary to chemotherapy.

Goal

The ultimate goal of any treatment is to improve your pet’s quality of life and your oncologist will work with you to determine the treatment option that you feel most comfortable with.

Image via Valeri Potapova/Shutterstock.com

Cancer of the Lymphocytes in Cats

Lymphoma is a type of cancer that originates in the lymphocyte cells. A type of white blood cell, lymphocytes play an important and integral role in the body's defenses in the immune system.

There are two forms of lymphocytes: B and T cells. Lymphoma may involve neoplastic proliferation of T or B, or non-B/non-T type lymphocytes, occurring primarily in the bone marrow, lymph nodes, and visceral organs.

Lymphoma is found to be responsible for around 90 percent of blood cancers and account for about 33 percent of all tumors in cats. Moreover, it is the most common cause of hypercalcemia in cats.

Symptoms and Types

Symptoms are highly variable and depend upon the anatomical form of this tumor. Following are some forms of lymphoma along with the related symptoms in cats:

Mediastinal form (occurs in the space between the pleural sacs/lungs)

• Open mouth breathing
• Cough
• Loss of appetite (anorexia)
• Weight loss

Alimentary form (occurs in the gastrointestinal tract, abdomen, liver)

• Anorexia
• Lethargy
• Vomiting
• Constipation
• Diarrhea
• Black or tarry stool
• Fresh blood in stool

Multicentric form (occurs in the lymph nodes)

• Swollen lymph nodes (i.e., jaw, under arms, groin)
• Loss of appetite
• Weight loss
• Depression

Solitary form (can occur in any location)

• Symptoms depend upon location

Renal Form (occurs in the kidneys)

Causes

The incidence of lymphoma is believed to be associated with exposure to feline leukemia virus (FeLV) and the feline immunodeficiency virus (FIV). Cats that have been infected with either of these viruses have a significantly higher rate of lymphomas than the general cat population.

Diagnosis

You will need to give your veterinarian a thorough history of your cat's health and onset of symptoms. The history and details you provide may give your veterinarian clues as to which organs are being primarily affected. Knowing a starting point can make diagnosis that much easier to pinpoint. Once the initial history has been taken, your veterinarian will perform a complete physical examination on your cat. Routine laboratory testing includes a complete blood count, biochemistry profile, and urinalysis.

The blood test results may show anemia, or the presence of an abnormally high number of lymphoblasts in the peripheral blood, a condition called lymphoblastosis. Lymphoblasts are immature cells which differentiate to form mature lymphocytes; they are normally present in the bone marrow, but if they proliferate uncontrollably they may  migrate to the peripheral blood, resulting in the abnormal condition called lymphoblastosis.

Biochemistry profiling may show an abnormally high creatinine, serum urea nitrogen, liver enzymes, and calcium levels. The urinalysis may reveal abnormally high levels of pigment bilirubin and proteins in the urine. Affected cats are also tested for the feline leukemia virus (FeLV), which is frequently associated with lymphomas. Your veterinarian will also use diagnostic imaging to locate the tumor(s), conducting X-rays of various body regions, especially the region that appears to be affected. A biopsy of the bone marrow will help in confirming the diagnosis conclusively.

Treatment

A cure is highly unlikely and there is no single treatment available to treat lymphomas. The major goal is to improve the quality of life for patients for as long as possible. Chemotherapy and radiotherapy can be used, but you will need to consult a veterinary oncologist  to determine if your cat is a good candidate for this type of therapy. It will depend on the stage of the lymphoma (early or advanced), the age of the cat, and your cat's overall well-being, amongst other considerations. Again, depending on the type and stage of the lymphoma, surgery may be performed in some patients. This may be a viable solution for some types of intestinal obstructions and for the removal of masses. A surgical incision would also allow your veterinarian to collect a specimen of the tumor for laboratory evaluation.

Living and Management

Unfortunately there is no cure available for this disease. The only resolution in some cases is to provide extra care to improve the quality of life in affected animals. It is important to closely monitor your cat’s food and water intake while it is in the recovery phase. Prognosis of this disease is highly variable and depends on the initial treatment response, anatomic type of tumor, FeLV status, and tumor burden.

If chemotherapy is initiated, you may need to take your cat for regular evaluations. At each visit your veterinarian will conduct blood testing to determine the treatment response and also to check the status of any complications that are occurring due to the treatment that is in place so that adjustments can be made as needed. If chemotherapy drugs have been prescribed as a part of home treatment, be sure to follow the directions closely, as chemotherapy medications are highly toxic to human health. Basic precautions include wearing latex gloves before drug administration. If pain medications for cats have been prescribed, use them with caution and follow all directions carefully, making sure that all members of the home are familiar with the medication schedule; one of the most preventable accidents with pets is overdose of medication. The survival time is highly variable, ranging from a few months to less than two years.