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Lymphoma in Cats

overview

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What is Lymphoma?

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Lymphoma is a common cancer seen in pet cats. Lymphoma can be caused by feline leukaemia virus (FeLV), though this is no longer commonly seen thanks to widespread vaccination. Lymphoma is more commonly seen in middle-aged to older cats, and there is no sex or breed predisposition.

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Different classifications of lymphoma exist, depending on where the cancer is located. The most common type affects the gastrointestinal tract, known as alimentary lymphoma, and makes up to 70% of cases. Less commonly, lymphoma can affect the peripheral lymph nodes (known as multicentric), the lymph tissue inside the chest cavity (known as mediastinal), or other sites such as the nasal cavity, kidneys or spine.

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Lymphoma is further classified based on the specific cell types affected. Up to 70% of cases are known as B-cell lymphoma, while the remaining 30% are known as T-cell lymphoma. This classification can affect the treatment we choose, and the expected response. Lymphoma can also be referred to as low, intermediate and high-grade depending on the behaviour of the cells and how quickly they are likely to progress.

symptoms

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What are the symptoms of Lymphoma in cats?

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Symptoms of alimentary lymphoma include weight loss, inappetence, lethargy, vomiting, and diarrhoea. Cats may have visible abdominal distension, and a mass may be palpable on examination. The intestinal loops often become thicker, and this may also be felt on examination.

Other symptoms depend on the type and location of the cancer. Cats with multicentric lymphoma typically have painless swelling of the lymph nodes, while those with mediastinal lymphoma may struggle to breathe as the lungs have less space than normal. Cats with renal lymphoma are often very unwell, with an increased thirst and urination. The kidneys may be swollen on examination. Cats with nasal lymphoma often have sneezing, runny eyes and may experience nose bleeds.

diagnosis

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What tests are used to diagnose Lymphoma in cats?

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The first step in any cat suspected of having lymphoma is full blood tests, including assessment of red and white blood cells, and testing for both FeLV and FIV (feline immunodeficiency virus). Blood tests show us changes secondary to the cancer and are important to guide treatment and prognosis.

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Ultrasound imaging is often performed to assess the abdominal organs, including the gastrointestinal tract and kidneys. In alimentary lymphoma the intestines may appear thickened, and abdominal lymph nodes may be enlarged. Ultrasound can provide a strong suspicion for alimentary lymphoma but is not conclusive, as inflammatory conditions such as IBD may cause the same visual changes.

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Definitive diagnosis of lymphoma is achieved by analysis of a biopsy sample. In the case of alimentary lymphoma, this means biopsies of the intestines, and abdominal lymph nodes if enlarged. Occasionally, it can be challenging to differentiate between alimentary lymphoma and severe IBD, even on a biopsy sample. Intestinal biopsy is not without some risk, so your vet will discuss if this is recommended. In multicentric lymphoma, a lymph node is often removed in its entirety and submitted to the lab for analysis. Occasionally, in the case of renal or mediastinal lymphoma, a diagnosis may be achieved using a fine needle aspirate rather than a surgical biopsy. This is unfortunately unreliable in alimentary and mediastinal cases.

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Depending on the case, we may wish to gather more information about the stage of disease before deciding on treatment options. This could include imaging of the chest, biopsy of bone marrow, and sampling of the organs such as liver and spleen.

treatment

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How is Lymphoma treated?

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Lymphoma is a systemic disease, with cancer cells spread throughout the body. As a result, we must treat the entire body to target all the abnormal cells. Lymphoma is treated using chemotherapy; however, several different protocols can be used. Broadly speaking, protocols involving several different drugs are more time-intensive and costly but carry better response rates. Your vet may wish to consult with a specialist oncologist before deciding on a treatment plan.

Most chemotherapy protocols for lymphoma involve a combination of injections in the clinic, and oral steroid tablets given at home. Chemotherapy injections may initially be given as often as weekly, but the frequency reduces as we see a response. Chemotherapy protocols can last anywhere from 4-18 months.

outlook

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What is the outlook for cats with Lymphoma?

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The prognosis for cats with lymphoma is very variable, depending on the type and the treatment undertaken. Without any treatment, the survival time after diagnosis is often only a few weeks as most cats are not diagnosed until they are unwell. If a full, multi-drug chemotherapy protocol is used, up to 70% of cats will respond and can reach a point of remission. Lymphoma does eventually recur, however, with around 30% of cases still doing well a year after starting therapy. There are several options in between, including both modified chemotherapy protocols and the use of steroids as a sole therapy. Although some cats do not respond at all to treatment, most will improve for at least a short time.