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Lymphoma is one of the most common cancers seen in dogs. Although there are breeds that appear
to be at increased risk for this disease, lymphoma can affect any dog of any breed at any age. It
accounts for 10-20% of all cancers in dogs.

Lymphoma (lymphosarcoma or non-Hodgkin's lymphoma) is a malignant cancer that involves the
lymphoid system. In a healthy dog, the lymphoid system is an important part of the body's immune
system defense against infectious agents such as viruses and bacteria. Lymphoid tissue normally is
found in many different parts of the body including lymph nodes, liver, spleen, gastrointestinal tract
and skin. Lymphosarcoma is classified according to the location in the body in which the cancer begins.

These include:

  • Multicentric form occurs in the lymph nodes.
  • Gastrointestinal form occurs in the stomach, intestines, liver and lymph nodes in the abdomen.
  • Mediastinal form occurs in the mediastinum, in front of the heart in an organ called the thymus.
    Hence this form of lymphosarcoma sometimes is called thymic lymphoma.
  • Cutaneous form occurs in the skin.
  • Acute lymphoblastic leukemia occurs when the disease starts in the bone marrow.
  • Miscellaneous forms of lymphosarcoma are less common and include those that begin in the
    nervous system, nasal cavity or kidneys.



While we understand how lymphomas form, we still do not understand why. There is growing evidence and much speculation
that environmental factors such as exposure to pesticides (especially herbicide 2,3-D) ( Read
New York Times Article: Lawn
Herbicide Called Cancer Risk for Dogs)
. A new study published in April 2012 finds that utilizing a chemical lawn service to achieve a
lush lawn is likely causing malignant cancer in many pet dogs. In the study, researchers identified 263 dogs with
biopsy-confirmed canine malignant lymphoma (CML), 240 dogs with benign tumors, and 230 dogs undergoing surgeries
unrelated to cancer. Then, they asked the pet owners to complete a 10-page questionnaire. Scientists found that dogs with
malignant lymphoma were 70 percent more likely to live in a home where professionally applied lawn pesticides had been used.
Dogs with the serious malignancy were also 170 percent more likely to come from homes where owners used chemical
insecticides to combat pests inside of the home.


Certain breeds of dogs have a higher than average risk of developing this disease and include Rottweilers, Scottish terriers,
Golden retrievers but lymphoma can afflict any breed of dog. Similarly, lymphoma can occur at any age, but the onset is
generally in middle and older age.


Most of the time, lymphoma in dogs appears as “swollen glands” (lymph nodes) that can be seen or felt under the neck, in front
of the shoulders, or behind the knee. Occasionally, lymphoma can affect lymph nodes that are not visible or palpable from
outside the body, such as those inside the chest or in the abdomen. Other symptoms include vomiting, diarrhea, loss of
appetite, weight loss, lethargy, difficulty breathing and increased thirst or urinations. Cutaneous lymphosarcoma can cause
redness or flakiness of the skin, ulceration (especially near the lips and on the footpads), itchiness or lumps in the skin. Clinical
signs will vary depending on the stage of the disease, volume of tumor and anatomic location of the lymphoma.


A thorough physical examination of the dog is an important part of the diagnostic work-up as it will dictate which further tests
will be required. The work up should always include a complete blood count (CBC), platelet count, biochemical profile,
urinalysis and fine needle aspirate or excisional or surgical biopsy of the lymph node. These tests help confirm the diagnosis
and determine if the dog is hypercalcemic and/or has normal neutrophil and platelet counts, and assess kidney function so
that chemotherapy can safely be administered. Lymphoma can also be diagnosed with x-rays and ultrasound The exact tests
performed will depend on the location of the tumor.

Once a diagnosis of lymphoma has been established, it is necessary that the cancer be staged. Staging is the process by
which the veterinarian determines to what extent the lymphoma has spread throughout the animal's body. The degree of
spread affects the manner in which a dog is treated.

Stage Definition

Stage I Involvement of a solitary lymph node or lymphoid tissue in a single organ (i.e. nasal cavity)
Stage II Several lymph nodes in the same general area involved
Stage III All peripheral lymph nodes involved
Stage IV Involvement of liver and/or spleen, and/or anterior mediastinum in the chest involved
Stage V Involvement of bone marrow (some classifications consider cutaneous involvement in this stage)

Substage a without systemic signs of disease (patient generally has no symptoms)
Substage b with systemic signs of disease (patient does not feel well)


Chemotherapy treatment is considered the gold standard for this aggressive form of cancer and usually consists of a
combination of oral and injectable drugs given on a frequent basis. The exact treatment protocol will vary depending on the
veterinarian and financial resources of the dog's family. There are several different chemotherapy protocols from which to
choose. They usually contain from 3-5 different chemotherapy drugs, each of which works on the cancer cells in a different way.
If some of the cancer cells are resistant to one drug, hopefully they will be sensitive to another drug.

The Wisconsin Lymphoma Protocol is a short, but intense chemotherapy regimen currently popular with oncologists as the
primary canine lymphoma treatment. This protocol involves weekly chemotherapy for the first 9 weeks and then every 2 weeks
until week 25. This chemotherapy protocol uses vincristine, doxorubicin (adriamycin), cyclophosphamide (cytoxan), and
1-asparagnase by IV, along with prednisone and/or cyclophosphamide orally. With the use of the 25 week University of
Wisconsin-Madison protocol, average first remission lasts 10-14 months, with 20% 2 year survival.

Doxorubicin alone : The patient is treated with a total of 5 treatments of doxorubicin at 3-week intervals. The average survival
time with this approach is 10-11 months.

COP: This protocol involves a combination of cyclophosphamide in tablet form, vincristine and prednisone. 4 weekly intravenous
injections of vincristine are given, followed by injections at 3-week intervals to complete 6 months of treatment.
Cyclophosphamide is given over 4 days every 3 weeks (4 days on; 17 days off). Prednisone is given daily for 6 months. The
average survival time with this protocol is reported as 8-10 months.

Prednisone alone : This medication is a steroid and can be given in pill form daily at home. The average survival time for
patients with lymphoma treated with prednisone only is 60 days.


Bone Marrow Transplants are now available for dogs with lymphoma at North Carolina State University’s College of
Veterinary Medicine.

Canine lymphoma is one of the most common types of cancer in dogs. While the survival rate with current treatments is extremely low (about 0 to 2
percent) the cure rate for dogs that have received a bone marrow transplant is at least 30 percent. The relatively new procedure involves the use of
leukaphoresis machines that are designed to harvest healthy stem cells from the peripheral blood. The machines are used in conjunction with drug
therapy to harvest stem cells that have left the patient's bone marrow and entered the bloodstream. The harvested cancer-free cells are then
reintroduced into the patient after total body radiation is used to kill residual cancer cells left in the body. This treatment is called peripheral blood
stem cell transplantation. The harvesting procedure itself takes six hours and the patient remains in the hospital for two weeks following the
procedure. The bone marrow transplant process is completely painless for dogs, although the dogs do experience some GI distress, manifested
mainly as diarrhea, from the total body radiation.

Dogs suffering from lymphoma are now able to receive the same medical treatment as their human counterparts through a new bone marrow
transplant procedure offered by the Veterinary Teaching Hospital at North Carolina State University’s College of Veterinary Medicine.

NC State’s CVM is the first veterinary program in the nation to offer canine bone marrow transplants in a clinical setting.

Bone marrow transplants for dogs can also be performed at these facilities currently in the United States:

  • North Carolina State University's College of Veterinary Medicine
  • Washington State University Veterinary School
  • Bellingham Veterinary in Bellingham, Washington
  • Gulf Coast Veterinary Specialists in Houston, Texas
  • VCA West Los Angeles Animal Hospital in Los Angeles, California
  • Veterinary Specialty Hospital in San Diego, California
  • Veterinary Specialty Center of the Hudson Valley in Wappingers Falls, New York

It must be noted that bone marrow transplants can not be performed on all dogs with lymphoma. Currently, the protocol requires that dogs be in
either complete remission or very close to complete remission before they can undergo bone marrow transplant treatment. Therefore, they need to
be treated first with chemotherapy.

Small dogs and dogs with existing health issues such as kidney or heart problems, or conditions that make infections more likely (e.g. diabetes,
Cushing's disease) may not be accepted as for bone marrow transplants due to complications that can arise


Some owners choose not to treat dogs that develop lymphoma. The life expectancy of these untreated dogs averages 4 to 6
weeks. Oral prednisone therapy may reduce the swellings and discomfort, but probably will not appreciably extend their life span. It
must also be noted that oral prednisone treatment prior to chemotherapy is not recommended and may actually reduce the
effectiveness of the chemotherapy.

In dogs that do undergo one of the recommended chemotherapy protocols, life expectancy can be extended. Most dogs with
lymphoma develop medium to high-grade lymphoma that is very responsive to chemotherapy. Greater than 75% of dogs with
lymphoma are expected to achieve a complete remission with chemotherapy. The duration of the first remission is variable,
depending on the chemotherapy protocol used, with median remission times varying from 6 months to 11 months. The second
remission is more difficult to achieve, with approximately 40% of dogs with lymphoma achieving complete remission with a second
course of chemotherapy. Less than 20% of dogs with lymphoma will achieve a third complete remission. Approximately 40-45% of
dogs with lymphoma live one year with treatment. Less than 20% of dogs with lymphoma live 2 years with treatment. Eventually,
the cancer will infiltrate an organ to such an extent that organ fails (often this is the bone marrow or the liver). The patient loses
his/her appetite, vomits or gets diarrhea, weakens and dies. At some point the tumor becomes resistant to therapy and no further
remissions can be obtained.

However, if a dog tolerates chemotherapy (fortunately most dogs do) their quality of life can be quite good during the treatment
period. Treatment for lymphoma in the dog is considered one of the more successful cancer treatments and can often be
performed by a local veterinarian without the need to travel long distances to veterinary schools or specialty clinics. It helps to
remember that one year can equate to almost 10% of a dog's expected life span, therefore, the increased life expectancy with
lymphoma treatment is often well worth it.