Nearly everyone in today's world has been affected by cancer to some degree. Either you have battled the vicious disease yourself or you know someone who has.
It's a tragic part of our lives, yet it has been somewhat normalized in a sense because it is so extremely common.
Sadly for our dogs, cancer doesn't discriminate. Just like people, many dogs will also have to face the disease in its various forms. In fact, studies estimate that over 25% of all dogs will be diagnosed with cancer at some point in their life.
Up to 50% of dogs over the age of 10 will die from cancer. This is beyond staggering. Therefore, it is important for dog owners to become aware of the telltale signs in order to recognize the condition before it's too late.
While there are many forms of cancer, lymphoma is among the most commonly diagnosed cancers in dogs. Therefore, understanding canine lymphoma will enable pet parents to quickly recognize signs and act efficiently to get their dog the help they need.
We know that a cancer diagnosis can be absolutely heartbreaking. However, by understanding your dog's condition, you can make informed decisions, with their happiness and wellbeing in mind.
We know that a cancer diagnosis can be absolutely heartbreaking. However, by understanding your dog's condition, you can make informed decisions with their happiness and wellbeing in mind.
What is Lymphoma in Dogs
Lymphoma is commonly diagnosed in people and dogs alike. Many veterinarians compare canine lymphoma to non-Hodgkin’s lymphoma in people.
In fact, the two conditions are so similar that nearly identical chemotherapy protocols are used to treat both dogs and humans.
Lymphoma is a blanket term used to diagnose cancers that stem from a white blood cell called lymphocytes. This white blood cell help the dog's immune system to effectively fight off infections.
Lymphocytes are found in high concentrations in areas of the body such as the lymph nodes, thymus gland, spleen, and within the bone marrow. It is important to note that lymphoma can occur anywhere in the body. However, it is found most prominently within the organs in which lymphocytes are found in high concentrations.
There are over 30 types of lymphoma in dogs, accounting for approximately 10–20% of all cancers diagnosed.
What is Lymphosarcoma or Non-Hodgkin’s Lymphoma
You may hear lymphoma also referred to as lymphosarcoma or non-Hodgkin’s lymphoma. We'll cover more detail on terminology in a moment!
What are Lymphocytes?
To reiterate, lymphocytes are the white blood cells responsible for supporting the immune system against infection.
What are Low Lymphocytes?
When you hear that your dog has a low lymphocyte count, it means they are highly susceptible to infection and disease. Low lymphocytes are often associated with cancers such as lymphoma.
Types of Lymphoma in Dogs
There are over 30 different types of lymphoma in dogs. The type of lymphoma will determine how quickly it progresses, possible survival rates, as well as clinical signs to look for.
Of the 30 different types of the disease, the four most common types are:
- Multicentric lymphoma
- Alimentary lymphoma
- Mediastinal lymphoma
- Extranodal lymphoma
Of the four types of lymphomas that we will cover, multicentric lymphoma is by far the most common.
In fact, multicentric lymphoma accounts for 80–85% of lymphomas in dogs. Multicentric lymphoma originates in the dog's lymph nodes. In many cases, the primary physical sign is visibly enlarged lymph nodes, sometimes up to ten times their normal size.
The enlargement typically doesn't cause your dog any pain, thus making an early diagnosis extremely difficult.
Alimentary lymphoma is the second most common type of lymphoma in dogs, although it only accounts for less than 10% of cases. Canine alimentary lymphoma primarily affects the dog's gastrointestinal tract.
Therefore, the signs of alimentary lymphoma in dogs are gastrointestinally related, as the disease causes intestinal lesions (more on that in a moment).
In rare cases, canine mediastinal lymphoma may be diagnosed. This form of lymphoma causes either the thymus and/or mediastinal lymph nodes in the dog's chest to become enlarged.
This enlargement is the result of high-grade malignant T-lymphocytes.
Finally, the fourth most common form of lymphoma is extranodal lymphoma. This type of lymphoma affects a specific organ (e.g., the eyes, kidneys, lungs, skin, central nervous system, etc.).
The most common organ that is affected by extranodal lymphoma is the skin. This form of the disease is also referred to as cutaneous lymphoma. Signs of extranodal lymphoma will vary greatly depending on which organ is affected.
What Causes Lymphoma in Dogs?
Even with advanced studies available, there are still many things about cancer in humans and dogs alike that remain unknown. Experts aren't able to pinpoint the exact cause of lymphoma in dogs, although studies have found that there are in fact certain breeds that are at a higher risk of the disease.
Furthermore, when genetics don't play a role in the diagnosis of lymphoma, we may assume that an environmental component is involved. Let us explain.
Studies have found that certain breeds have a predisposition for the development of canine lymphoma (more on that in a moment).
However, when many breeds not included among the high-risk list also develop the disease, experts must consider other possibilities of the underlying cause.
What do all of these dogs have in common, other than lymphoma? In many cases, the answer is their environment.
Pet parents may not fully realize the extent to which their dog's environment may include a substantial number of toxins that can greatly affect their dog.
Toxins from things like paints or solvents, as well as pesticides, herbicides, and insecticides can all play a role in the health of your dog's immune system. In many cases, experts are linking these toxins to diseases such as cancer.
Additional possible causes of canine lymphoma include:
- Viruses and/or Bacteria
- Weakened Immune System
Breeds at Higher Risk for Canine Lymphoma
Studies show that the current breeds are at a higher risk of canine lymphoma:
- Scottish Terriers
- Basset Hounds
- Saint Bernards
- Golden Retrievers
Additionally, studies have found that certain breeds, including Dachshunds and Pomeranians, have a lower risk of developing canine lymphoma.
Canine lymphoma is most commonly diagnosed in middle-aged dogs, approximately 6–9 years old.
With that said, it is important for dog owners to understand that any dog, regardless of the breed, may develop lymphoma.
Being able to recognize the signs of the disease will help to expedite an accurate diagnosis and determine the best form of treatment for your dog's individual needs.
Signs of Lymphoma
The signs of canine lymphoma will vary based on the type of lymphoma present. Unfortunately, this can make an early diagnosis more difficult in some cases.
General Signs of Lymphoma
In most cases, regardless of the type of lymphoma, the following general signs will be present:
- Swollen lymph nodes under the jaw, in front of the shoulders, or behind the knees
- Swelling of the face
- Swelling of the legs
- Excessive thirst
- Excessive urination
Signs of Multicentric Lymphoma
If the dog has the most commonly diagnosed form of lymphoma, multicentric lymphoma, the first sign that pet owners will typically recognize is swollen lymph nodes.
In many dogs, it is common for the lymph nodes to swell up to ten times their normal size. Although it looks painful, swollen lymph nodes do not typically cause the dog any distress. They will feel like rubbery lumps and will be able to move freely under the skin.
As multicentric lymphoma progresses, dog owners will also notice the following signs:
- Lack of appetite and weight loss
Signs of Alimentary Lymphoma
Alimentary lymphoma attacks the dog's intestines. Signs of alimentary lymphoma are a result of gastrointestinal lesions and often include:
- Severe abdominal pain and sensitivity
- Weight loss
Signs of Mediastinal Lymphoma
Mediastinal lymphoma can cause a large mass to develop in the chest. Therefore, a common sign of the disease is difficult or labored breathing. Additional signs include:
- Swelling of the face
- Swelling of the front legs
- Increased thirst
- Excessive urination
Mediastinal lymphoma in dogs can also cause a muffled heart sound, which your veterinarian will be able to hear with a stethoscope.
Signs of Extranodal Lymphoma
Signs of extranodal lymphoma in dogs will ultimately vary depending on which organ is affected. For example, extranodal lymphoma that affects the lungs will often cause respiratory problems to develop. Extranodal lymphoma that affects the eyes can lead to blindness. When extranodal lymphoma affects the kidneys, it can lead to renal failure.
The most common type of extranodal lymphoma, cutaneous lymphoma, affects the skin, therefore, the associated effects would also be evident on the skin.
Many times, pet owners will find single or multiple raised nodules or scaly lesions on the dog's body, both of which can be indicative of cutaneous lymphoma.
The raised bumps may also be found in the dog's mouth, specifically on the gums, lips, or the roof of the mouth. It is common for the disease to be mistaken for an allergy for several months before an accurate diagnosis is made.
Additional signs of cutaneous lymphoma include:
- Dry, red, flaky patches of skin
- Large masses or tumors
- Skin ulcers
How is Lymphoma Diagnosed?
Diagnosing lymphoma early on can be rather difficult, as the disease often doesn't cause the dog any pain unless it affects the bones. Therefore, by the time the dog receives a diagnosis, the disease can be quite advanced.
Typically, a series of diagnostic tests will be the first step in order to accurately diagnose lymphoma in dogs. These diagnostic tests include:
- Blood tests
- Fine needle aspirate* of the tumor
- Complete blood count (CBC)
- Blood chemistry panel
- Abdominal sonograms
What is a Fine Needle Aspirate?
Besides biopsies of the tumor(s), another diagnostic tool used to diagnose lymphoma in dogs is something called a fine needle aspirate.
The procedure allows veterinary oncologists (veterinarians who specialize in cancer patients) to safely remove a small sample of the dog’s lymph nodes or affected organs.
Once removed, the vet will be able to examine the sample through either a cytological exam (looking for abnormal white blood cells) or through histopathological evaluation (of the tissue).
Stages of Lymphoma in Dogs
The World Health Organization has developed a system for staging cancer, and this system is also used to stage lymphoma in dogs. During the diagnostic process, your vet will classify your dog's disease as one of five stages. Treatment and prognosis will ultimately depend on the stage of the disease.
- Stage I: Single lymph node is involved
- Stage II: Multiple lymph nodes within the same region are affected
- Stage III: Multiple lymph nodes in multiple regions affected
- Stage IV: Liver and/or spleen involved (it is possible to not have lymph node involvement although in most cases there is)
- Stage V: Bone marrow or blood involvement and/or organs other than the liver, spleen, and lymph nodes affected
Additionally, veterinarians will also categorize the disease as either substage A or substage B.
Substage A refers to cases in which the dog shows no sign of illness. Substage B refers to cases in which the dog does show signs of illness.
Treatment for Lymphoma
Unfortunately, there is presently no known cure for canine lymphoma. With that said, it is a treatable type of cancer in dogs. Most commonly, chemotherapy drugs are the preferred treatment option.
Chemotherapy is also proven to be the most effective treatment for canine lymphoma. The type of chemotherapy treatment will vary based on the type of lymphoma.
For example, multicentric lymphoma in dogs is often treated with a chemotherapy protocol over 25 weeks, referred to as UW-25. Your veterinary oncologist will be able to tell you exactly which treatment is best for your dog's individual needs.
Chemotherapy for Dogs vs. Chemotherapy for People
As we previously mentioned, lymphoma in dogs is often compared to non-Hodgkin’s lymphoma in people. Interestingly enough, the treatment for both (varying chemotherapy methods) is also closely related.
Fortunately for our dogs, chemotherapy doesn't seem to affect them nearly as negatively as it does people. Chemotherapy doesn't typically make dogs severely sick and dogs generally don't lose their hair.
Dogs with thick fur, such as Poodles, Old English Sheepdogs, and the Bichon Frise (which are generally not predisposed to lymphoma) may lose more hair than most other breeds.
Side Effects of Chemotherapy in Dogs
The following are side effects associated with chemotherapy in dogs:
- Lack of appetite
- Mild bouts of vomiting and/or diarrhea
Additional Treatment for Lymphoma
Depending on the type of lymphoma and the stage of the disease, radiation therapy and/or surgery may be recommended.
Additionally, your veterinarian may recommend things like dietary changes, physical therapy, or nutritional supplements in order to provide extra support during treatment.
Lymphoma Survival Rate
Of course, one of the leading questions that pet parents have about their dog's diagnosis is what they should expect in terms of median survival rate and life expectancy. Unfortunately, the answer is not always clear and simple. Lymphoma in dogs may vary greatly from case to case.
The prognosis will ultimately depend on the type of lymphoma, as well as the stage in which it was diagnosed. The prognosis for lymphoma in dogs will also depend on the treatment option chosen.
For instance, if the pet owner cannot afford, or chooses not to use a treatment like chemotherapy, it can greatly affect the projected life expectancy of dogs with Lymphoma.
Remission vs Cure
It is also imperative that pet owners realize that there is a difference between complete remission and a cure. Total, complete remission means that there are no clinical signs of cancer.
However, cancer could still exist within the body. A cure means that the body is completely free of the disease. Partial remission also exists and is a term used to describe a patient that shows some, but not all the signs of cancer.
Additionally, research has found that certain dogs tend to have a better prognosis. For instance, studies have shown that neutered females have a better prognosis and longer survival times.
Lymphoma in Dogs: A Final Thought
At the end of the day, receiving a lymphoma diagnosis can be a very challenging time for a dog owner. We wish our canine friends could live forever - and with a lymphoma diagnosis, it can seem like our time with them is about to be stopped in its tracks.
Trust us, we know how difficult it is and we are truly sorry that some of our readers may have to face this.
With that said, we want pet owners to understand that canine lymphoma is one of the most treatable cancers in dogs.
Every day, advancements in science and holistic medicine are making great strides forward. So many canine cancers that were once considered to be a death sentence are now being successfully treated. Lymphoma is listed among these diseases.
One of the most important things that dog owners can do is to stay alert. By understanding your dog's normal day-to-day behavior and tendencies, you'll be able to pick up on when something isn't right.
Furthermore, if and when you notice that something is off with your dog, don't delay in getting your dog an accurate diagnosis. A timely trip to the vet can make a world of difference for your furry companion.
From all of us at Honest Paws, we hope your beloved four-legged friend gets well soon.
Petal Smart is a veterinarian who, after a brief stint in clinical practice, has been a medical, veterinary, and science editor for the past four years. She has edited hundreds of research studies that have been published in various academic journals, and more recently, she has been editing blog articles on pet health. She holds a DVM (Hons) from the University of the West Indies - St. Augustine. Her pets in the past have included dogs, fish, birds, and a turtle. At times, she also likes to think of herself as a horse whisperer. You can connect with her on LinkedIn.
*This article has been edited and updated for publication by Petal Smart, DVM.