By Dr. Becker
This is great news!
A new diagnostic test developed by two companies in the U.K. is able to detect whether a dog with lymphadenopathy, or inflammation of the lymph nodes, is suffering from lymphoma or another illness.
The two companies, Tridelta Development Ltd. and Petscreen Ltd., formed a joint venture to introduce the Tri-Screen Canine Lymphoma Assay Kit.
The Purpose of Lymph Nodes
Lymph nodes are small masses of tissue found throughout the body. Your dog's immune system depends on these little glands to filter blood and store white blood cells.
Lymph node abnormalities are often one of the first signs of a disease process at work in the tissues of the body.
Inflamed tissues drain into lymph glands, causing them to also become inflamed and swollen as the number of white blood cells increases in response to the presence of infection. This response is called reactive hyperplasia -- it occurs when there's an increase in production of white blood cells and plasma cells.
The result is enlarged, inflamed lymph nodes. (The correct technical term for lymph node enlargement is actually lymphadenomegaly, but lymphadenopathy is used interchangeably and is the more commonly used name.)
Lymphadenopathy can involve swollen lymph nodes beneath the skin that can be felt (palpated), it can involve internal lymph nodes that must be imaged to be seen, or both.
Inflammation can be localized, involving just one gland or glands in a single region of the body, or it can be widely distributed.
Causes of Swollen Lymph Nodes
There are a number of things that can cause enlargement of lymph nodes. Since cancer is one of them, it's extremely important to determine the cause of the inflammation.
Lymphoid hyperplasia is a condition in which the lymph nodes produce an excess of white blood cells in response to an infection elsewhere in the body. Lymphadenitis is an infection of the lymph nodes themselves, either as the primary disease or a secondary condition. Fungal infections and a wide range of bacterial infectious agents can trigger inflammation of lymph glands. So can an allergic reaction, immune-mediated disease and other non-infectious causes.
It's worth noting that lymphadenopathy can also result in the shrinkage of lymph glands. This is seen in cases of canine senility, cachexia (physical wasting away from loss of weight and muscle mass), viral infection, and immune-mediated disease that reduces the amount of lymph node tissue.
Lymph glands can also be diseased without being enlarged.
Signs and Symptoms
Swollen lymph glands can often be felt beneath the jaw, around the shoulder area, the back of the leg, behind the knee joint and in the groin.
Most enlarged lymph nodes feel firm, can be moved around under the skin, don't cause pain and are a normal temperature. However, if the dog has lymphadenitis (infection of the nodes themselves), the glands more often feel soft and warm to the touch, and cause tenderness. They are also more apt to be fixed rather than movable.
Extremely enlarged lymph nodes – from five to ten times larger than normal – are more often associated with lymphoma (cancer of the lymph nodes), metastatic neoplasia (cancer elsewhere in the body that has spread), or lymphadenitis.
If there are swollen nodes in the abdomen, it can make bowel movements difficult. Severely enlarged glands can make it hard for a dog to eat, or sometimes to breathe.
Nausea and the urge to throw up after eating can result in loss of appetite. Fever is common, and many dogs just feel generally miserable as their body attempts to fight off the infection.
Lymphoma is actually a word used to describe a group of cancers that originate from lymphocytes (white blood cells).
Lymphocytes are a normal part of the immune system and help protect your dog's body from infection. Lymphoma can invade any organ in the body, but it most often affects organs that are part of the immune system such as bone marrow, the spleen, and of course, lymph nodes. The most common type of the canine form of the disease is multicentric lymphoma. The cancer is first spotted in the lymph nodes, especially those under the dog's jaw.
Other common types of the disease in dogs include:
- Alimentary or GI lymphoma (stomach and/or intestines) causes vomiting and watery diarrhea which can be very dark in color and foul-smelling. Weight loss is also common with this type of lymphoma.
- Mediastinal lymphoma (chest organs, such as lymph nodes or the thymus gland) typically involves difficulty breathing, either due to a large mass or an accumulation of fluid in the chest cavity. Dogs with this type of lymphoma can also have swollen faces or front legs, and increased thirst and urination.
- Cutaneous lymphoma, which involves the skin. This type of lymphoma starts as dry, flakey, red patches of skin, and progresses to angry red, thickened skin with ulcerations. It can also develop orally and involve the gums, lips and roof of the mouth. Cutaneous lymphoma is frequently misdiagnosed in its early stages as either a skin infection/allergy or if it's in the mouth, gum disease.
Since enlarged lymph nodes can derive from such a wide variety of problems inside the body, diagnosis usually involves a number of different tests.
Your veterinarian will perform a physical exam on your dog and take a complete health and symptom history. This can sometimes provide clues as to which organs beyond the lymph nodes might be involved.
With the new Tri-Screen Canine Lymphoma Assay Kit, a vet can get same day results from a simple blood test that provide an immediate determination of whether the lymph node problem is or is not cancer. The sooner lymphoma is detected and treatment begun, the better the prognosis.
This new test can also avoid delays in treating lymphoma resulting from a conservative approach -- for example, starting the dog on a course of antibiotics, assuming the problem is an infection rather than a malignancy.
It also circumvents the need for definitive lymphoma diagnosis through an invasive biopsy. This procedure uses either fine needle aspiration or excising (cutting into) the lymph node to remove tissue for testing. A biopsy also requires that the dog be heavily sedated or anesthetized, and there is usually some pain involved following the procedure.
The new test should also be extremely useful for dogs without palpable swollen lymph nodes who are exhibiting other symptoms commonly associated with diseases of the lymph glands.
If the diagnosis is indeed lymphoma, staging tests are recommended to determine how extensive the cancer is. These tests can include blood tests, urinalysis, chest and abdominal x-rays, sonogram of the abdomen, bone marrow aspirate, and fine needle aspirate of organs that appear abnormal on imaging.
For dogs that do not have lymphoma, a chemical blood profile, complete blood count, blood smear, electrolyte panel and urinalysis may be performed.
Other tests that may be advisable are blood serum tests for antibodies to fungal or bacterial agents, x-rays and/or ultrasound imaging.
Cases of lymphadenopathy that are not lymphoma-related are typically treated medically, depending on the underlying cause of the inflammation.
Holistic practitioners use a wide range of modalities, from Chinese herbals such as Wei Qi Booster and Stasis Breaker, to intravenous vitamin C nutraceuticals and homeopathics.
Canine lymphoma is treated in conventional veterinary medicine with chemotherapy, and in some cases, surgery or radiation treatment may also be recommended.
One of the two companies offering the Tri-Screen test also offers 'directed chemotherapy,' which is a lab service that determines the best chemo protocol for a particular lymphoma. The drawback is a biopsy of tumor tissue must be taken in order to test various chemo solutions against it to see which is/are most effective.
So while you can avoid the biopsy with the new blood test, if it turns out your pet has canine lymphoma and you decide to go the chemotherapy route, I highly recommend a biopsy and use of the directed chemo service. Otherwise, the veterinarian(s) treating your pet are left to guess at which chemo drugs to use. This seems like an unnecessary risk under the circumstances, so my advice is to take advantage of the directed chemotherapy service.
Dogs tend to tolerate chemo better than humans. They don't feel as ill for as long, and only a few breeds experience hair loss. About 70 to 90 percent of dogs with multicentric lymphoma treated with the chemo drug UW-25 experience partial or complete remission of the cancer.
Unfortunately, in most dogs, the lymphoma will recur. A second round of UW-25 brings about a second remission in the majority of these dogs, but it is of shorter duration than the first remission because the cancerous cells grow resistant to chemo drugs.
The prognosis for dogs with lymphoma depends on what type of lymphoma is present and what type of chemotherapy is used. The average length of survival of dogs with multicentric lymphoma treated with UW-25 is from 9 to 13 months. Some dogs live much longer, while others don't live long at all.
Chemotherapy for lymphoma is expensive – typically several thousand dollars for the first round.
Helping Your Dog Stay Healthy
As is the case with all cancers, the scientific community hasn't yet figured out the combination of triggers that creates canine lymphoma. However, the immune system is clearly implicated in both human and canine forms of the disease.
Steps you can take to help your own beloved companion be as healthy as possible include: