Lymphoma in dogs is one of the most common forms of canine cancer. Fortunately, it’s also one of the most treatable, earning it the #1 spot as the most overall commonly treated cancer in veterinary medicine today. Although canine lymphoma is classified as a malignant cancer (meaning it can spread and become fatal), if it’s caught early, it has one of the most successful treatment rates in dogs (more on that later).
What Is Lymphoma?
Lymphoma, also called lymphosarcoma, is a cancer that affects specialized white blood cells called lymphocytes, which are part of the body’s immune system. The lymphocytes’ responsibility is to recognize foreign invaders in the body like viruses, fungi, and bacteria. Once a threat is identified, the lymphocytes immediately go to work making specific proteins called antibodies that attack these invaders and destroy them as quickly as possible before they can cause serious damage.
Sometimes, the DNA inside the lymphocytes can become damaged, which causes the cells to mutate. These mutated cells can then “go rogue” and start replicating themselves, invading other areas of the immune system such as the lymph nodes, spleen, and bone marrow. This results in the cancer commonly known as lymphoma.
Canine lymphoma is more commonly seen in middle-aged to older dogs between 6 and 9 years old, but it can occur at any age. Certain breeds such as Boxers, Basset Hounds, Bulldogs, Saint Bernards, Bull Mastiffs, Airedales, Golden Retrievers, Rottweilers, and Scottish Terriers seem to have higher rates of lymphoma; however, any dog can be affected. It’s believed that spayed female dogs who are diagnosed with lymphoma seem to have a better prognosis than males.
Forms Of Lymphoma In Dogs
There are several different forms of lymphoma in dogs, and each is named for the area it affects. The 5 most common are:
Multicentric lymphoma – affects the lymph nodes
Cutaneous lymphoma – affects the skin
Gastrointestinal lymphoma – affects the gastrointestinal tract
Mediastinal lymphoma – affects the lymph tissues surrounding the heart and lungs
Central Nervous System (CNS) lymphoma – affects the brain and spinal cord. CNS lymphoma usually results when multicentric lymphoma spreads.
Multicentric lymphoma is the most common type of lymphoma in dogs. It may spread to other organs and cause healthy tissue to become diseased, eventually resulting in organ failure.
Stages of Canine Lymphoma
Cancer in both dogs and people is usually “staged” at the time it’s diagnosed. That is, it’s put into specific categories, with Stage 1 being the mildest form of the disease and Stage 5 the most severe. Here’s how lymphoma in dogs is staged:
Stage 1: The cancer is confined to one single lymph node.
Stage 2: The cancer is confined to one certain group of lymph nodes in a specific area of the body.
Stage 3: There are multiple areas of enlarged lymph nodes throughout the body.
Stage 4: The cancer has spread to the liver and/or spleen, causing them to become enlarged.
Stage 5: The cancer is present in the bone marrow, central nervous system, and/or other sites in the body besides the liver/spleen.
Symptoms Of Lymphoma
Most of the time, lymphoma in dogs appears as swollen lumps (which are actually enlarged lymph nodes) in and around the dog’s neck, behind the knees, or in the shoulder area. Other signs vary based on the type of lymphoma present and the stage of the disease.
Other signs can include:
- Loss of appetite
- Weight loss
- Difficulty breathing
- Increased thirst
- Increased urination
- Redness, flakiness, or ulcers on the skin, usually around the lips and footpads (cutaneous form)
Diagnosing Lymphoma In Dogs
Oftentimes dog parents aren’t aware there’s a problem until they happen to come across a swollen lymph node under their dog’s skin. Any lumps that you find on your dog should be checked by a veterinarian as soon as possible. Since weight loss is also one of the most common symptoms of cancer in dogs, any dog who is not eating well or losing weight for no apparent reason should also be seen by a veterinarian.
To help diagnose lymphoma, a veterinarian will first examine the dog, checking his or her gum color (to make sure it isn’t pale, indicating the dog may be anemic), checking the dog’s temperature, and manually feeling all areas where groups of lymph nodes are present for any sign of enlarged lymph nodes. Next, the veterinarian will usually collect both blood and urine samples to run laboratory tests. Blood work will show whether the number of lymphocytes present in the bloodstream is too high or too low, and whether the cells themselves look abnormal under the microscope. The vet can also use a needle to collect cells directly from a lymph node to examine them microscopically.
An ultrasound can also be done to see if the liver, spleen, or certain lymph nodes in the abdomen appear to be enlarged.
Treatment for Lymphoma
Treatment for dogs with lymphoma depends on many factors, including the form of lymphoma present, the stage of the cancer, and the age and health status of the dog. However, the most effective overall treatment seems to be chemotherapy. Most dogs diagnosed with lymphoma are treated with a combination of chemotherapy drugs that are administered through an IV over a series of several scheduled visits, along with the steroid prednisone. Unlike humans, dogs seem to tolerate chemotherapy quite well, without many of the side effects that people often experience.
There are also other treatment options now being used in addition to chemotherapy that include antibody therapy, bone marrow and stem cell transplant therapy, and immunotherapy, which helps boost the dog’s immune system so it can better fight the cancer. Radiation therapy can also be given to patients after chemotherapy is completed, if needed.
If chemotherapy treatment is cost-prohibitive, or if a dog parent decides not to pursue treatment due to the dog’s age or health status, the steroid prednisone can be used alone to make the dog more comfortable until the disease has progressed to its final stage.
Prognosis For Dogs With Lymphoma
As mentioned earlier, out of all types of canine cancer, lymphoma has one of the best responses to treatment. Standard chemotherapy treatment results in remission (where dogs are no longer experiencing symptoms and the cancer no longer shows up on medical tests) in approximately 60-90% of cases, with a median survival time of 6-12 months. In approximately 20-25% of cases, some dogs can live 2-3 years (or longer) after treatment. However, without treatment, prognosis is very poor – most dogs will succumb to the disease within 4 to 12 weeks.
Although lymphoma in dogs responds very well to chemotherapy, it’s important to understand that entering into remission does not mean the lymphoma is cured. Most dogs who undergo successful chemotherapy treatment will eventually come out of remission. Once that happens, the lymphoma seems to be more resistant to chemotherapy, and the drugs used to fight the cancer become less effective.
What To Do If Your Dog Is Diagnosed With Lymphoma
If your dog is diagnosed with lymphoma, first keep in mind that every case of canine cancer is different, and there is no one decision that is best for every dog and every dog parent. Whether you decide to pursue treatment will depend on your dog’s age, overall health, whether you feel your dog will tolerate the treatment, and as much as we humans hate the idea, your present financial situation. It helps to ask yourself, “What is best for my dog?” Ask as many questions of your vet that it takes until you are sure you have all the information necessary to make an informed decision. You must make the best decision you can based on the knowledge that you have, not only of treatment options, but of every unique and individual factor that makes up your dog. Whatever you decide, examine your heart and do what you know is right for your dog.
If you decide to pursue treatment, the first thing to do is to ask your veterinarian for a referral to a board-certified veterinary oncologist who specializes in treating cancer in pets. The oncologist will work closely with you to develop the best treatment plan for your dog. Don’t be afraid to ask as many questions as it takes in your first meeting so you understand exactly what the treatment will look like and what to expect afterwards. And before the first meeting, although it might be tempting to want to try to do everything you can to help, avoid starting your dog on any new vitamins or supplements, since some of these can potentially interfere with chemotherapy drugs.
If you decide not to pursue chemotherapy, there are still many ways to give your dog the best quality of life possible during this time. Talk with your veterinarian about developing an end-of-life care plan especially customized for your dog. This article on palliative care for dogs also has helpful tips for how to best help dogs who are approaching end-stage cancer and make them as comfortable as possible.
Can Lymphoma In Dogs Be Prevented?
When it comes to lymphoma, there is still much we don’t understand. We know how it starts and spreads, but we still don’t understand exactly what causes it. Interestingly, there seems to be growing evidence that environmental factors such as exposure to lawn care products (especially those containing the herbicide 2,4-D) and pesticides is heavily linked to an increased risk of lymphoma in dogs. According to the Canine Cancer Website, a study published in 2012 showed that dogs with canine lymphoma were 70 percent more likely to live in a home whose owners used a chemical lawn service. Even more disturbing, these dogs were 170 percent more likely to live in homes where chemical pesticides were used inside the house to help control pests.
Since dogs are much more sensitive to environmental toxins than we are, it makes sense to do everything we can to limit their exposure not only to pesticides and lawn care products, but also to other environmental factors such as chemical cleaning supplies, new carpeting (which contains the known cancer-causing chemicals formaldehyde, benzene, and toluene) and second-hand cigarette smoke.
It’s now estimated that a staggering 50 percent of dogs will develop cancer during their lifetime. Anything within our control that we can change to help lower their risk is well worth the effort!
Have you ever had a dog who was diagnosed with Lymphoma? Please share your story with us in the comments below!