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Lymphoma in cats

Lymphoma is the most common malignant cancer in cats. This disease affects the lymphocytes and lymphoid tissue (lymph nodes, spleen, and bone marrow), which are crucial parts of the immune system. While the prognosis is poor, early detection and appropriate treatment might help manage the disease for years and improve your cat’s quality of life.

While the exact cause of the disease is still unknown, it is well known that certain factors may increase a cat’s risk of getting lymphoma, such as feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV). Exposure to environmental toxins, such as tobacco, and a compromised immune system may also contribute to the development of this cancer. On the other hand, there is no known breed, age, or gender predisposition.

As lymphoma affects the lymphocytes, which spread throughout the body, the cancerous cells can develop in different organs, including lymph nodes, gastrointestinal tract, liver, skin, spleen, kidneys, eyes, and bone marrow. Thus, the symptoms of lymphoma can vary depending on the affected organs. The signs can be quite nonspecific, so further testing is usually required. The most common signs include:

  • Enlarged lymph nodes (felt as lumps under the skin)
  • Weight loss
  • Loss of appetite
  • Lethargy
  • Vomiting and diarrhoea
  • Increased thirst and urination
  • Respiratory distress
  • Palpable masses in the abdomen or lymph nodes

Depending on the main location of the tumour, lymphoma can be classified into different types. Some cats can also have more than one site of lymphoma involvement.

  • Gastrointestinal lymphoma: This is the most common form of the disease in cats and is frequently seen in senior cats. The affected areas include the stomach, intestines, liver, and the lymph nodes surrounding the intestines. Common clinical signs include loss of appetite, weight loss, lethargy, vomiting, and diarrhoea. These signs, as well as the results obtained from some diagnostic tests, might be indistinguishable from cats with inflammatory bowel disease (IBD). In such cases, an intestinal biopsy might be required to reach a definitive diagnosis.
  • Mediastinal lymphoma: This type of lymphoma involves the lymph nodes located in the cranial part of the chest. It is more common in young to adult cats and is strongly linked to infection with FeLV. The clinical signs are usually evident when the lymph nodes become enlarged enough to compress the surrounding structures or if there is an accumulation of fluid around the lungs. Apart from nonspecific signs, respiratory difficulties may also be noticed.
  • Kidney lymphoma: This type of lymphoma may affect one or both kidneys. The clinical signs are usually linked to kidney failure, such as increased thirst and urination, vomiting, loss of appetite, and/or enlarged kidney(s).
  • Nasal lymphoma: A lump located in the nasal cavity. It usually presents with sneezing and nasal discharge.
  • Multicentric lymphoma: This type of lymphoma is not as common in cats as it is in dogs. It usually affects the external lymph nodes, which will be evident when you touch their skin under the neck, behind the knees, in front of the shoulders, or in the abdomen.
  • Other sites: Lymphoma in cats occasionally involves other areas of the body, including the central nervous system (brain, spinal cord, nerves), eyes, and skin.

As the signs of lymphoma can be quite nonspecific, initially, your cat will undergo a thorough physical examination, and further testing will be required to either confirm or exclude other differential diagnoses. This might include a complete blood test, urinalysis, chest x-rays, microscopic analysis of the affected tissue, and/or abdominal ultrasound.
The diagnosis of lymphoma is usually obtained by finding cancerous cells under microscopic examination. Usually, your veterinarian will start with a fine needle aspirate (FNA) of the affected tissue. This sample will be obtained by using a needle to aspirate cells from the tissue. This test usually has minimal risk for the patient and can be performed on a conscious cat. While an FNA is usually enough to diagnose lymphoma, it won’t provide information regarding the grade of the disease (which is highly linked to the aggressiveness of the lymphoma and response to treatment). For this reason, a biopsy of the affected tissue is considered the gold standard diagnostic test for this disease, as the results are more reliable, and it also provides information about the type and grade of the lymphoma. Unfortunately, biopsies need to be performed under general anaesthesia, which might not be a suitable option for every patient.
Once the diagnosis of lymphoma is confirmed, screening for metastasis in other parts of the body is recommended to understand the severity/prognosis of the disease.

The treatment approach for lymphoma in cats will vary depending on different factors, including the type of lymphoma, extent of the disease, and the overall health of your cat. Common treatment options include:

  • Chemotherapy: This is the most common treatment for lymphoma in cats. While this is not a cure, in some cases, chemotherapy can lead to remission (temporary resolution of the signs) for several years in up to 75% of the cats treated. Usually, a combination of drugs is required, some of which could be administered orally at home. Chemotherapy is well tolerated in most cats, and the side effects are normally less severe than those observed in human beings.
  • Radiation Therapy: Radiation may be recommended to target localised lymphoma (frequently used in nasal lymphoma). When more than one area is affected, it is recommended to combine radiation with chemotherapy.
  • Surgery: Surgical intervention may be necessary in specific cases to remove lumps or obtain biopsy samples. This is usually in addition to chemotherapy.
  • If the mentioned treatments are not an option for your pet, cats can be treated palliatively with steroids. While the prognosis in this case is noticeably decreased compared with other types of therapy, this treatment usually helps with temporary improvement of the disease for a few months. It is also a more affordable treatment and can be easily administered at home.

Lymphoma usually cannot be cured, but in some cases, the patient can go into a remission stage, sometimes staying in remission for several years. Once the patient has finished the course of chemotherapy and has gone into remission, it is recommended to continue with regular vet checkups to screen for early signs of lymphoma recurrence.

While the prognosis will vary depending on the type and location of the lymphoma, as well as individual patient response, there are some prognostic factors that might give us an idea of how the disease might progress over time:

  • If the patient is sick at the moment of the initial diagnosis, the prognosis is usually poor. If the patient seems well, the prognosis is improved, and chemotherapy is usually well tolerated.
  • Concurrent infections with a feline virus (FeLV or FIV) are usually linked to a lower prognosis.
  • Location of the tumour → worse prognosis for kidney and central nervous system lymphoma, better prognosis in nasal lymphoma.
  • Good response to treatment is usually associated with a better prognosis for the disease.
  • Poorer prognosis once bone marrow, liver, and spleen are also involved.

For intermediate and high-grade lymphomas, the average survival time for cats undergoing chemotherapy is approximately 6–8 months. On the other hand, for low-grade lymphomas treated with chemotherapy, the average survival times are around 18 months. When chemotherapy is not attempted, the average survival time is usually less than 4 weeks. It is important to consider that these numbers are only an average among the affected population, and some cats may live for shorter or longer periods.

Cat lymphoma is a complex disease, but with early detection, proper diagnosis, and appropriate treatment, it is possible to manage and improve your cat’s well-being. If you are concerned about your cat’s health, don’t hesitate to contact us.