Lymphoma is the most common cancer diagnosed in cats. It arises from abnormalities in the white blood cells called lymphocytes. It can occur almost anywhere in the body, and although it often responds well to treatment, it is rarely fully cured.
Lymphocytes are found all through the body, both in the lymph nodes (glands) and in the bloodstream. This is why if they become cancerous, a mass can grow anywhere in the cat. However, some areas are more commonly affected than others are. The tumors are usually given four classifications:
- Alimentary Lymphoma - which affects the intestinal system
- Mediastinal Lymphoma - which occurs in the chest cavity.
- Multicentric Lymphoma - which occurs in lymph glands and can affect multiple areas all over the body.
- Extranodal or Miscellaneous Lymphoma - this describes tumors that occur in other places; for example, the kidneys or the brain.
The cause of the cancer is usually unknown, as it is with most kinds of tumors. However, cats that are carrying the Feline Leukemia Virus or the Feline AIDS virus are more vulnerable to developing it.
The symptoms of Lymphoma will vary depending on where the tumor is growing. Common signs to look out for include weight loss, poor appetite, lethargy, vomiting, diarrhea, and drinking more than usual.
Often your vet will locate a mass when they examine your cat by feeling enlarged lymph nodes (most commonly under the chin or in the back legs) or by palpating their abdomen and feeling a lump. The next step in diagnosis is to take blood tests. These will show changes in the levels of white blood cells and usually a big spike in the numbers of lymphocytes. Your vet will then likely move on to either X-rays or scans. This will allow them to see the tumor and assess its size and position. The vet may also choose to perform a bone marrow biopsy.
If possible, it is also a good idea to be able to take a sample of the tumor, or even attempt removal if that is possible (which is most often with the alimentary type but it is unlikely to be curative). With a sample, your vet can order extra tests to categorize the mass fully. This will have an impact on the type of treatment that would be best and will affect the overall prognosis.
Once all of this has been done, your vet will be able to discuss potential treatments with you, which can include surgery, chemotherapy, and radiotherapy. Many pet parents worry about the side effects of the latter, particularly if they have experience or knowledge of people going through similar treatments. However, our pets generally have far fewer problems and usually your veterinarian is able to put your mind at rest.
If the cancer is too advanced or you do not wish to proceed down these routes, they will also be able to talk about palliative and end of life care. Although for many cats, treatments will send them into remission, most will have a relapse and succumb to the Lymphoma in the end. However, medications can give them a great quality of life in the meantime.
Unfortunately, there is very little we can do to help prevent Lymphoma in our cats, other than ensure they are vaccinated against Feline Leukemia, and if possible, Feline AIDS. Since vaccinations have become much more common, the incidence of Feline Lymphoma has fallen significantly.