Lymphoma in animals is a
malignant cancer originating from lymphocytes, which are an important
component of the immune system. Lymphoma also occurs in humans. The
disease occurs in lymph nodes, bone marrow, and organs such as the
liver, spleen, eye, skin, and gastrointestinal system. It is also known as lymphosarcoma.
Lymphoma in a Golden Retriever
Cytology of lymphoma in a dog
Lymphoma in dogs
Lymphoma is one of the most common malignant
tumors to occur in dogs. The cause is genetic,
but there also suspected environmental factors involved.
The cancer is classified into low and high
grade types. Classification is also based on location. The four location types
are multicentric, mediastinal, gastrointestinal, and extranodal (involving the
kidney, central nervous system, skin, heart, or eye). Multicentric lymphoma, the
most common type, is found in the lymph nodes, with or without involvement in
the liver, spleen, or bone marrow. Mediastinal lymphoma occurs in the lymph
nodes in that area and possibly the thymus. Gastrointestinal lymphoma occurs as
either a solitary tumor or diffuse invasion of the stomach or intestines, with
or without involvement in the surrounding lymph nodes, liver or spleen.
Classification is further based on involvement of B-lymphocytes or
General symptoms include depression, fever, weight loss, loss of appetite,
Hypercalcemia (high blood calcium levels) occurs in some cases of lymphoma, and
can lead to the above symptoms plus increased water drinking, increased
urination, and arrhythmias.
Multicentric lymphoma presents as painless enlargement of the peripheral
lymph nodes. This is seen in areas such as under the jaw, the armpits, the
groin, and behind the knees. Enlargement of the liver and spleen causes the
abdomen to distend. Mediastinal lymphoma can cause fluid to collect around the
lungs, leading to coughing and difficulty breathing. Hypercalcemia is most
commonly associated with this type. Gastrointestinal lymphoma causes vomiting,
melena (digested blood in the stool).
Lymphoma of the skin is an uncommon occurrence. An important type originating
from T-lymphocytes is
mycosis fungoides. It can have a wide variety of appearances, from a single lump
to large areas of bruised, ulcerated,
Symptoms for lymphoma in other sites depend on the location. Central nervous
system involvement can cause
seizures or paralysis. Eye involvement can lead to glaucoma, uveitis, bleeding
within the eye, retinal detachment, and blindness. Lymphoma in the bone marrow
causes anemia, low platelet count, and low white blood cell count.
Biopsy of affected lymph nodes or organs confirm the diagnosis. X-rays,
ultrasound, blood analysis, amd bone marrow biopsy reveal other locations of the
cancer. The stage of the disease is important to treatment and prognosis.
Stage I - only one lymph node or
lymphoid tissue in one organ involved.
Stage II - lymph nodes in only one area of the body involved.
Stage III - generalized lymph node involvement.
Stage IV - any of the above with liver or spleen involvement.
Stage V - any of the above with blood or bone marrow involvement.
Each stage is divided into those with systemic symptoms (loss of appetite,
weight loss, etc.) and those without.
Complete cure is rare with lymphoma, but long
remission times are possible with chemotherapy. With effective protocols,
average first remission times are 6 to 8 months. Second remissions are shorter
and harder to accomplish. Average survival is 9 to 12 months. The most common
treatment is a combination of cyclophosphamide, vincristine, prednisone, L-asparaginase,
and doxorubicin. Other chemotherapy drugs such as chlorambucil, lomustine (CCNU),
cytosine arabinoside, and mitoxantrone are sometimes used in the treatment of lymphoma by themselves
or in substitution for other drugs. In most cases, appropriate treatment
protocols cause few side effects, but white blood cell counts must be monitored.
When cost is a factor, prednisone used alone can improve the symptoms
dramatically, but it does not significantly affect the survival rate. The
average survival times of dogs treated with prednisone and untreated dogs are
both one to two months. Using prednisone alone can cause the cancer to become
resistant to other chemotherapy agents, so it should only be used if there is
definitely no chance of further treatment.
Lymphoma with a
high grade generally respond better to treatment. Dogs with B-lymphocyte tumors
have a longer survival time than T-lymphocyte tumors. Mediastinal lymphoma has a
poorer prognosis than other types. Otherwise, the stage of the disease is the
best prognostic factor.
Lymphoma in cats
Lymphoma in young cats occurs most frequently following infection with
feline leukemia virus (FeLV) or to a lesser degree feline immunodeficiency virus (FIV). These cats tend to have involvement of
lymph nodes, spine, or mediastinum. Cats with FeLV are 62 times more likely to
develop lymphoma, and cats with both FeLV and FIV are 77 times more likely.
Older cats tend to have gastrointestinal lymphoma without FeLV infection. The
same forms of lymphoma that are found in dogs also occur in cats, but
gastrointestinal is the most common type. Lymphoma of the kidney is the most
common kidney tumor in cats, and lymphoma is also the most common heart tumor.
Symptoms for multicentric, mediastinal, and extranodal lymphoma are similar
to dogs, except hypercalcemia is rare. The most common sites for
gastrointestinal lymphoma are, in decreasing frequency, the small intestine, the
stomach, the junction of the ileum, cecum, and colon, and the colon. Symptoms
include vomiting, diarrhea, weight loss, loss of appetite, and melena. The tumor
can also cause life-threatening blockage of the intestine. Anemia is a common
problem in all cats with lymphoma. Lymphoma of the kidney presents as bilateral
kidney enlargement and failure. Lymphoma of the heart causes congestive heart
failure, pericardial effusion, and arrhythmias.
Diagnosis is similar to dogs, except cats should be tested for FeLV and FIV.
Treatment and prognosis
Chemotherapy is the mainstay of treatment for lymphoma in cats. Most of the
drugs used in dogs are used in cats, but the most common protocol uses
cyclophosphamide, vincristine, and prednisone. The white blood cell count must
be monitored. Remission and survival times are comparable to dogs. Lower stage
lymphoma has a better prognosis. Multicentric lymphoma has a better reponse to
treatment than the gastrointestinal form, but infection with FeLV worsens the
Lymphoma in ferrets
Lymphoma is common in
ferrets and is the most common cancer in young ferrets. There is some evidence
that a retrovirus
may play a role in the development of lymphoma like in cats. The most commonly
affected tissues are the lymph nodes, spleen, liver, intestine, mediastinum,
bone marrow, lung, and kidney.
In young ferrets, the disease progresses rapidly. Symptoms include loss of
appetite, weight loss, weakness, depression, difficulty breathing, and coughing.
It can also masquerade as a chronic disease such as an upper respiratory
infection or gastrointestinal disease. In older ferrets, lymphoma is usually
chronic and can exhibit no symptoms for years. Symptoms seen are the same as in
young ferrets, plus
splenomegaly, abdominal masses, and peripheral lymph node enlargement.
Diagnosis is through biopsy and x-rays. There may also be an increased
lymphocyte count. Treatment includes surgery for solitary tumors, splenectomy
(when the spleen is very large), and chemotherapy. The most common protocol uses
prednisone, vincristine, and cyclophosphamide. Doxorubicin is used in some
cases. Chemotherapy in relatively healthy ferrets is tolerated very well, but
possible side effects include loss of appetite, depression, weakness, vomiting,
and loss of whiskers. The white blood cell count must be monitored. Prednisone
used alone can work very well for weeks to months, but it may cause resistance
to other chemotherapy agents. Alternative treatments include vitamin C and Pau
d'Arco (a bark extract).
The prognosis for lymphoma in ferrets depends on the their health and the
location of the cancer. Lymphoma in the mediastinum, spleen, skin, and
peripheral lymph nodes has the best prognosis, while lymphoma in the intestine,
liver, abdominal lymph nodes, and bone marrow has the worst.
Ettinger, Stephen J.;Feldman, Edward C.(1995).Textbook of Veterinary
Internal Medicine(4th ed.). W.B. Saunders Company.
Hillyer, Elizabeth V.;Quesenberry, Katherin E. (1997). Ferrets,
Rabbits, and Rodents: Clinical Medicine and Surgery (1st ed.). W.B.
Morrison, Wallace B. (1998). Cancer in Dogs and Cats (1st ed.).
Williams and Wilkins.