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Feline Lymphoma
Victoria Larson DVM
Diplomate American College of Veterinary Internal Medicine (Oncology)
Lymphoma or lymphosarcoma is a cancerous disease of lymphocytes, a type of white blood cell that
originates in the lymph nodes and bone marrow. The cancerous lymphoma cells can spread to other
lymph nodes and to major organs. Cats are unusual in that most often lymph nodes are not involved
and instead the disease is found in either major organs or the gastrointestinal tract (these are known
as extranodal sites.)
There are several different types of lymphocytes. Some are called B-cells (Bursa cells), which
produce antibodies, and some are called T-cells (Thymus cells), which signal additional chemical
defenses of the body to ward off an infectious attack. A lymphoma of T-cell origin will have a poorer
prognosis and will often have an associated high calcium level in the blood. At this time, a tissue
sample of the cancerous mass must be surgically removed to be tested in order to determine whether
the lymphoma is B- or T-cell. Most cats have a lymphoma of T-cell origin.
Lymphoma accounts for 1/3 of all tumors seen in cats making it the most common tumor in the feline
patient. In about 30% of cats that develop lymphoma the cancer can be directly attributed to an
infection with the feline leukemia virus. In all other cats with lymphoma a cause is not known. Cats
infected with the feline leukemia virus generally have a poorer prognosis because they are more
susceptible to complications associated with treatment and may develop tumors in multiple sites. The
incidence of feline leukemia has been decreasing steadily over the years because of readily available
tests and vaccines.
Clinical signs of lymphoma can vary greatly in cats. An external mass may be seen or cats may show
non-specific signs including lethargy, weakness, a decreased appetite, weight loss, diarrhea,
shortness of breath, difficulty swallowing, increased thirst or increased urination. The liver, spleen,
kidneys, mediastinum, intestinal tract, bone marrow, eye, central nervous system, nose and skin can
all be affected.
Either mass aspiration or a biopsy of a mass can be used to make the initial diagnosis of lymphoma.
An aspirate is a relatively non-painful procedure using a small needle to obtain cells to be examined
under the microscope. An aspirate can be done quickly and requires no sedation or anesthesia. A
biopsy is where a tissue sample of the mass is obtained at surgery. This is done if the results of the
aspirate are not diagnostic or if the type of lymphoma (B or T cell) needs to be determined.
Staging of lymphoma is a process recommended for all patients following diagnosis. Staging
determines how advanced the cancer is at the time of diagnosis. Commonly ordered tests include a
complete blood count, serum chemistry analysis, urinalysis and chest and abdominal x-rays or
-2ultrasound. Bone marrow aspiration is a diagnostic procedure to determine if the lymphoma has
spread to the bone marrow. If lymphoma is found in the bone marrow, this means that the lymphoma
has reached an advanced or leukemic stage.
The mainstay of lymphoma treatment is combination chemotherapy in which a variety of medications
are given according to a specific plan or protocol. Many chemotherapy protocols exist and they are
frequently modified or updated. Cats do moderately well with chemotherapy. The most common side
effect seen with chemotherapy in cats is loss of appetite. Up to half of all cats treated with
chemotherapy may experience a significant decrease or complete loss of appetite associated with
treatment. If the appetite loss continues for greater than 3 to 5 days a temporary (naso-esophageal)
or permanent (PEG) feeding tube may need to be placed. Cats that are not eating well when
chemotherapy treatments are initiated are also more likely to suffer from this complication. Cats also
may experience a thinning of the hair coat – particularly on the head – and whisker loss. These
changes are purely cosmetic and do not affect the pet’s quality of life. There is a less than 5% chance
of severe vomiting, diarrhea, or infection, which could require hospitalization and a small risk of death,
associated with severe complications.
The goal of treatment of lymphoma is aimed at remission of the disease and not a cure. A remission
is defined as no external evidence of lymphoma based on the physical exam and laboratory tests.
Without treatment, cats on average will live 4 to 6 weeks. If placed on prednisone alone, several
weeks may be added to this. Cats with a lymphoma have a 60% chance of going into a complete
remission when treated with combination chemotherapy and, on average, remissions last 6 to 9
months. If a solitary site is involved (for example a single skin mass or a nasal mass) chemotherapy
may be combined with surgery or radiation therapy. Cats with a single site have a better prognosis
and survival of greater than a year is not uncommon.