The lymphomas (malignant lymphoma or lymphosarcoma) are a diverse group of cancers that originate from a type of white blood cell called a lymphocyte.
They are one of the most common cancers diagnosed in dogs and cats. This cancer usually arises in lymph tissues such as lymph nodes (lymph glands), spleen, and bone marrow; however, it can arise in almost any tissue in the body including the skin, the brain or spinal cord, bones, heart, or intestines.
In the cat, it is most commonly found in the intestinal tract. Lymphoma can occur in any breed. Middle-aged to older dogs and cats are most commonly affected; however, young cats that carry the feline leukaemia virus may also develop lymphoma.
Because lymphoma can affect any tissue in the body, symptoms can be vague and may reflect the organ that is involved. Signs of lymphoma can include generalised lymph gland swelling and enlargement (most easily felt under the jaw, in front of the shoulder and behind the knee), loss of appetite, weight loss, vomiting and/or diarrhoea, lethargy, excessive drinking, skin lumps
Most dogs with lymphoma still feel fine and the glandular enlargements are often noticed incidentally by the owner, the groomer, or the veterinarian during routine examination. In the cat, most cases involve the intestinal tract so diarrhoea and weight loss are the most common symptoms in that species.
In most cases a needle aspirate or biopsy of the affected organ(s) is required to make the diagnosis.
This usually involves a biopsy or removal of a lymph gland in dogs as that is the most common organ involved. In cats and dogs with the intestinal form of the disease, biopsies may be obtained through the use of a fibre optic scope or an abdominal exploratory surgery.
Additional tests may be required to more accurately determine the prognosis in each individual. Certain test results are known to predict whether a particular dog or cat is likely to respond to therapy.
Your veterinarian will also ask a pathologist to determine if the lymphoma is a “high” or “low” grade subtype. This will help determine how aggressive the treatment will be. Additionally, blood tests to assess the overall health of the pet are important because the disease usually occurs in older animals that may have complicating diseases such as diabetes, kidney, heart, or liver disease.
In general, most pets with lymphoma have involvement of multiple glands and/or multiple organs, so called “multicentric” lymphoma.
Therefore most treatment types available involve medications that go to all parts of the body (i.e., chemotherapy). The gold standard of care for multicentric lymphoma is a combination of four or five chemotherapy drugs given into the vein in an alternating fashion either weekly or every other week. Individual outcomes can be better predicted if the cell type, grade, organ involved, and stage are known.
Using single-agent chemotherapy can result in remissions; however, the length of the remission is shorter than in multi-drug protocols.
For those clients who choose simple steroid therapy (e.g., oral prednisone), responses tend
to be only a month or two in length.
If you have any concerns about your pet’s health please contact your veterinary surgery for advice.
If your dog is displaying any of the symptoms above be aware that some of these are non-specific and your vet will need to examine the animal and decide on a treatment plan.
Michael Morrow owns and runs St Vincents Veterinary Surgery, an independent practice providing personal care for pets in and around Wokingham since 2005. For more information call us on 0118 979 3200 or visit www.stvincentsvets.co.uk
