Lymphosarcoma (lymphoma) is a malignant cancer originating in lymphocytes, which are found in lymph nodes and pretty much all the organs and tissues around the body. It is probably the most common type of cancer in cats and not uncommon in dogs. Like most cancers, middle-aged to older animals are most at risk. However, lymphoma is unique in that it can be associated with feline leukaemia virus (FeLV) infection in cats. Cats that are infected with FeLV can develop feline lymphoma as young as three years of age.
As lymphocytes and lymphoid tissues are found all over the body, lymphoma can occur anywhere. In cats, the most common sites are the lymph nodes, gastrointestinal system, inside the chest cavity and the kidneys. In dogs, the lymph nodes, liver and gastrointestinal tract are the most common sites.
Signs of the disease are often non-specific and usually relate to the system that is affected. If multiple lymph nodes are affected, the lymph nodes may be seen or felt as ‘lumps’, for example behind the jaw, in the groin and in front of the shoulders. If the gastrointestinal tract is affected, the pet may be vomiting or have diarrhea with or without blood in the feces. Renal (kidney) lymphoma may manifest as excessive drinking or urination over a period of time and there may be blood in the urine. There may also be non-specific signs such as weight loss and lethargy.
The first step to diagnosing lymphoma is a biopsy. In some cases, a fine needle aspirate may confirm the disease. The vet may then recommend a surgical or ultrasound-guided biopsy for histopathology in order to differentiate between the two types of lymphoma, B-Cell and T-Cell lymphoma.
The silver lining to lymphoma is that it responds fairly well to chemotherapy compared to other types of cancers. Chemotherapy can be expensive and there can be side effects, however these are often not as bad as in humans and we have a good chance of achieving remission with lymphoma.
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