Lymphoma in Cats
Feline lymphoma is one of the most common cancers in cats, and typically affects the gastrointestinal system. It is most often seen in senior cats, and the prognosis and treatment depends on the type of lymphoma diagnosed – small or large cell lymphoma. Small cell lymphoma may be managed for some time with medication, whereas large cell lymphoma typically requires surgery and chemotherapy, and has a poorer prognosis.
In This Article
Lymphoma is a malignant cancer of lymphocytes, which are cells of the immune system. These cells travel throughout the body via the lymphatic system.
Cats may develop different types of lymphoma, including:
Gastrointestinal (GI) lymphoma: This is by far the most common type of feline lymphoma, and results in gastrointestinal symptoms such as weight loss, vomiting, diarrhea, and appetite changes.
Lymphoma outside the gastrointestinal tract: As lymphocytes are present throughout the body, lymphoma can develop in any organ, particularly the lymph nodes, chest cavity (mediastinal lymphoma), kidneys (renal lymphoma), liver, spleen, central nervous system, eyes, skin, nose (nasal lymphoma), or blood.
This article will focus on gastrointestinal lymphoma, which is the most common type of lymphoma in cats.
The two types of GI lymphoma are small cell lymphoma (SCL) and large cell lymphoma (LCL). SCL is also known as lymphocytic or low-grade lymphoma. LCL is also known as lymphoblastic or high-grade lymphoma. Gastrointestinal lymphoma is more common in older cats, who are 9-13 years of age.
Symptoms of GI lymphoma in cats may include:
Weight loss/poor body condition
Cats with small cell lymphoma (SCL) may begin to display symptoms gradually over time. The signs of SCL are similar to signs of Inflammatory Bowel Disease (IBD), and many cats diagnosed with IBD are diagnosed with lymphoma in the future.
Cats with large cell lymphoma (LCL) usually present with more acute and more severe signs. Cats with LCL may suddenly stop eating, develop a fever, and be very lethargic.
There is no known cause for gastrointestinal lymphoma in cats. Researchers believe that chronic inflammation from diet or environmental toxins, such as tobacco ingested through grooming, may cause mutations which can lead to cancer.
In terms of diagnosis, your veterinarian will first feel your cat’s abdomen to assess if the intestines appear thickened or if there is an obvious tumor within the abdominal cavity. Laboratory work including a chemistry to assess total body function, complete blood count to assess white blood cell count and anemia status, and urinalysis should be performed in all cats. Vitamin B12 levels (cobalamin) are often low in cats with gastrointestinal disease so this is often measured as well. Once this baseline is obtained, more specific diagnostic tests are performed. These include:
Abdominal ultrasound: This is a non-invasive test that usually does not require any sedation. In cases of LCL, distinct mass(es) are visible within the abdominal cavity. In cases of SCL, characteristic changes in the intestinal wall layering and thickening of the muscularis (smooth muscle) layer of the intestine may be visible. Abdominal lymph nodes can also be assessed to see if they are enlarged (lymphadenopathy). While it is very useful, the ultrasound is not a definitive test for lymphoma and it cannot differentiate between SCL/LCL and IBD without further testing.
Fine needle aspiration and cytology: If a distinct mass is seen in the abdomen, a fine needle aspirate might be obtained and submitted for a cytology (examination of the cells). This means that a small needle is used to collect a sample of cells from the tumor. This can usually be performed with very mild sedation. The cytology may tell the veterinarian what type of cells are present within the tumor and might provide information about how malignant or aggressive it is. This test often cannot be performed in cases of SCL as there are usually no defined tumors present, and it may not be able to provide a definitive diagnosis.
Biopsy: During a biopsy, the veterinarian removes one or more small samples of tissue that are submitted to the laboratory for testing. A biopsy is performed under general anesthesia, and has the advantage of being able to provide information on the grade of lymphoma, based on how rapidly the cancerous cells are dividing. (Low grade lymphoma is easier to treat and will result in a quicker and longer-lasting remission than high grade lymphoma.) There are two different types of biopsy:
Endoscopic: An endoscope (small camera) is passed into the intestines through the oral cavity and small tissue samples are collected. The downside of this procedure is that the biopsies are not full thickness, meaning that we don’t know how deep the cancerous cells extend. In addition, the samples are small and not all of the intestinal tract can be assessed.
Surgical: A surgeon opens the abdomen and obtains samples from multiple sites. These samples are full thickness and the surgeon can visualize the entirety of the GI system.
The treatment for lymphoma in cats varies depending on the type of lymphoma.
Small cell lymphoma in cats (SCL): In most cases, cats are managed with a combination of prednisolone (steroid) and chlorambucil (oral chemotherapy drug). Vitamin B12 supplements are provided if needed. This may be injectable B12 given under the skin weekly for 6 weeks, then monthly. Alternatively, a daily oral supplement may be used. Probiotics are recommended to restore your cat’s gastrointestinal flora, and your veterinarian may recommend dietary changes as well.
Large cell lymphoma in cats (LCL): These cats are usually treated with surgery, chemotherapy, and sometimes radiation. The most common chemotherapy treatment is known as ‘CHOP’, which stands for cyclophosphamide, doxorubicin, vincristine, and prednisolone. It involves weekly chemotherapy injections and daily oral prednisolone administration. It is important to remember that cats do not suffer the same side effects of chemotherapy as humans do. While their white blood cell counts may decrease, they usually do not experience the severe nausea, inappetence, fur loss, and malaise reported by human chemotherapy patients.
Is there a cure for lymphoma in cats?
Unfortunately, there is no cure for lymphoma. This condition can only be managed, to minimize symptoms and prolong your cat’s life for a number of months or years.
Is lymphoma contagious to humans or other pets?
No. Lymphoma is not contagious to humans or other pets.
What is the cost of treating feline lymphoma?
The initial diagnostics (bloodwork and ultrasound) can cost several hundred dollars. Biopsies can cost a few thousand, with surgical biopsies typically more expensive than endoscopic ones. You should also be aware of ongoing medication, check-up and diagnostic costs.
When a cat is diagnosed with SCL, they will remain on daily oral medication for the rest of their life. Prednisolone is an inexpensive medication, however, chlorambucil is more expensive. They will require frequent recheck visits and bloodwork, typically every 3-4 months when stable. Repeat ultrasounds are also required to monitor for disease progression.
For cats with LCL, treatment costs may run into thousands of dollars for chemotherapy and/or radiation treatment.
The prognosis for gastrointestinal lymphoma in cats depends on the type of lymphoma. Small cell lymphoma (SCL) may be managed for some time with medications, B12 supplementation, dietary modification, and probiotics. 70% of cats with SCL will achieve remission and the median survival time is 23-30 months.
Unfortunately the prognosis for large cell lymphoma (LCL) is significantly lower, with only 50-70% of cats achieving remission with aggressive chemotherapy, surgery, and radiation, and a median survival time of 2-9 months. If chemotherapy/surgery is not an option, prednisolone (steroid) therapy alone may be used.
Lymphoma cannot be prevented. However, certain steps can be taken to decrease the risk of lymphoma. These include vaccinating cats for Feline Leukemia Virus (FeLV) (if warranted), minimizing environmental toxins, and having senior cats examined by a veterinarian at least twice yearly. Cats should be taken to a veterinarian immediately if they start vomiting or having diarrhea, lose weight, have a decreased appetite, or seem lethargic.
Is there a vaccine for feline lymphoma?
No. There is no vaccine for gastrointestinal lymphoma. Given that certain types of lymphoma in cats, especially mediastinal lymphoma, are related to FelV, the FeLV vaccine may be administered to at-risk cats.
Gastrointestinal lymphoma is a common type of cancer of older cats. The two types of GI lymphoma are small cell lymphoma and large cell lymphoma. Small cell lymphoma is similar to IBD in cats. It is often a chronic condition, which can be managed with oral medication. Large cell lymphoma is often a more acute condition, which carries a poorer prognosis. Clinical signs of lymphoma include weight loss, decreased appetite, vomiting and diarrhea. A senior cat should be taken to the veterinarian at least twice yearly, or more frequently if exhibiting the above signs.