Lymphocytes are normal defensive immune system cells which travel around the body, with each one devoted to combatting a different virus, bacterium or parasite, together comprehensively protecting the whole body. If one of these cells mutates and becomes cancerous, then lymphoma is the most common resulting disease. Some breeds are predisposed, such as any breeds with a short nose, retrievers and Siamese cats. Most cats and dogs are older when they develop lymphoma.
The best treatment for each individual pet depends on a number of features.
Stage, is an assessment of how extensive the disease is. The location of the lymphoma is significant in terms of predicting spread, the symptoms that will arise, the overall outlook including lifespan, and therefore the treatment which is best in response. Sometimes all the mutated lymphoma cells are present in one location, such as in most cases of nasal lymphoma, meaning that radiation therapy of just the nose is a comprehensive therapy for them. However, just as healthy normal lymphocytes can travel around the body, lymphoma cells often are able to travel too, and some nasal lymphoma patients will be found to have lymphoma cells outside the nose, which results in chemotherapy being a more comprehensive treatment for them than radiation therapy. This might sound scary, but side effects are actually very unusual in cats- please see our chemotherapy overview section for more details.
Testing can be offered to look for the spread of lymphoma such as x-rays, ultrasound, needle samples of organs, maybe bone marrow sampling. Dr Elders will discuss with you how much testing is advisable, and sometimes no such tests are needed. Blood and urine samples can be useful both for assessing spread and to see the impact of the lymphoma on your cat, sometimes revealing features that need to be addressed promptly such as a high calcium level.
Grade is an assessment of aggressiveness of the tumour cells made by microscopic assessment. The size of the individual tumour cells can be seen on a needle sample, and size and the grade of the lymphoma are often aligned with large cells being associated with a high grade, aggressive lymphoma. However, grade is a more comprehensive assessment of the lymphoma cells than merely their size, and often requires a surgical biopsy of the lymphoma, perhaps with removal of a mass or a lymph node. Depending on where a tumour is, a biopsy through a scope might be another option.
Phenotype is a term which mainly describes the origin of the lymphocyte which has been mutated, such as B (for those originating in the bone marrow) or T (for those originating in the thymus). This information can be determined from any needle or biopsy sample of lymph node tissue. Flow cytometry is an antibody-based method of assessing needle samples, and provides the T or B status of a lymphoma as well as several other features of the phenotype which can impact the anticipated outlook for a dog or cat, and the best treatment choices.
If there is any confusion as to whether the problems in your dog might not be lymphoma but might actually be caused by a beneficial but excessive immune response, we can offer a PARR test. This test assesses the how related the cells are at the genetic level.
The aim of treatment in most cats and dogs is to significantly extend lifespan with a normal quality of life, through the least frequent visits.
Some clients prefer not to have chemotherapy and we can offer supportive medication to improve quality of life and lifespan without chemotherapy too. Finally, veterinary research is ongoing, and Dr Elders will be able to discuss any novel developments which might have occurred since this document was written, including new treatments and vaccines.