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Updated May 16, 2024 – Lymphoma is one of the most common pet cancers, accounting for (by some estimates) a staggering 24% of all cancers diagnosed in dogs.   

Given how common lymphoma is in dogs, dog owners need to understand the common signs of lymphoma and the basics of diagnosis and treatment to make the best and most informed decisions for their pets.      

What is Lymphoma?  

Lymphoma is a cancer of a type of white blood cell found in both the blood and the lymphatic system. In dogs, researchers have described more than 30 types of lymphoma, and the different subtypes significantly vary in behavior, treatment approaches and long-term prognosis.  

Although lymphoma can strike any breed of dog at any age, the disease most commonly affects:  

  • Middle-aged to older dogs (average age 6 to 9 years old)  
  • Males and females equally  
  • Boxers, bull mastiffs, basset hounds, Saint Bernards, Scottish terriers, Airedales, golden retrievers and bulldogs   

Signs of Lymphoma   

  • Early in the disease, the signs or symptoms of lymphoma can be very subtle or mimic other diseases. The most commonly reported signs are:  
  • Weight loss  
  • Lethargy  
  • Anorexia  

None of these signs are specific to lymphoma. Still, some forms of lymphoma can result in swollen lymph nodes, vomiting and diarrhea (if abdominal organs are involved), and difficulty breathing (if the cancer is affecting the lymph nodes in the chest). Owners may feel or see an enlarged lymph node(s).     

Diagnosis   

Diagnosis requires a combination of bloodwork, imaging (such as ultrasound), aspirates of enlarged lymph nodes or internal organs and biopsy. Since the prognosis depends on the type of lymphoma present, special testing of the cancerous cells is important.   

In many cases of lymphoma, your veterinarian can make a diagnosis with a simple aspirate of cells from an enlarged lymph node.   

Further testing to determine the type of lymphoma present can help with treatment and long-term prognosis. Unfortunately, many dog owners and their veterinarians skip this step because additional testing can be expensive. However, as we learn more about lymphoma, this extra step can make a big difference for the patient and their caretaker.    

There are many reasons for determining subtype:  

  • Different forms of lymphoma have other risk factors. Understanding the lymphoma subtype will help us better understand the causes.  
  • By subtyping canine lymphomas, we can draw parallels to their human counterparts. Dogs can benefit from new therapies developed in human patients.  
  • Different forms of lymphoma have dramatically different outcomes, and subtyping can help inform owner decisions about treatment.  

Lymphoma Isn’t Just One Disease but Many  

For a long time, veterinarians treated lymphoma as a single disease. The development of sophisticated diagnostic techniques allowed researchers to look at lymphoma more closely, and they quickly learned that there are many different subtypes of the disease, each with its unique features and treatment response.   

This discovery confirmed what many veterinary oncologists already knew – patient outcomes were varied even when their cancers appeared the same.   

We’re still learning more about each type of lymphoma, but it’s clear that knowing the specific type of lymphoma is necessary for treatment and survival.   

Let’s start with the most basic division of lymphoma type – whether the cancer arises from T or B cells. We know that lymphocytes are a type of white blood cell and an essential part of the immune system. We also know that lymphocytes are either B cells, which produce antibodies, or T cells. T cells perform many other functions, including regulating immune processes and killing abnormal cells (for example, cancer cells or cells infected with viruses or bacteria). Lymphoma can arise when either B cells or T cells start to divide uncontrollably.   

Knowing whether a lymphoma is predominantly B or T cell in origin is essential for prognosis and treatment. Each form has aggressive and less aggressive subtypes, and diagnostic testing can provide crucial additional information.   

One way to determine the lymphoma subtype is a test called flow cytometry. Fresh cells are aspirated from a suspect lymph node or organ and sent to a unique laboratory for review.    

Your veterinarian may also take a biopsy of an affected lymph node or organ and send the specimen to a pathologist for additional evaluation. This step is more involved since it requires tissue collection, but it is the only way to accurately diagnose some lymphoma subtypes.  

Once veterinarians perform diagnostic testing, they will identify one of several lymphoma subtypes. 

Some of the most common are:  

  • Peripheral T-cell lymphoma – this common form usually starts with enlarged lymph nodes but often affects other organs. Dogs with this form of lymphoma have an average survival time of around seven to eight months with chemotherapy.  
  • Diffuse large B-cell lymphoma is the most common form of lymphoma in dogs. This form of lymphoma presents in the same way as T-cell lymphoma, but the prognosis with chemotherapy is much better, with average survival times of 12 to 24 months.  
  • T-zone lymphoma – unlike peripheral T-cell lymphoma, this type of lymphoma has excellent long-term survival, with many dogs living three or more years, sometimes with no chemotherapy.  

Precursor lymphoma/leukemia — tumors derived from immature lymphocytes are the most aggressive form, with median survival times measured in days, even with treatment. Cytology and histology cannot distinguish this type of lymphoma from mature B- and T-cell lymphoma. Flow cytometry is the only method capable of making this distinction. 

Other less common types of lymphoma include cutaneous lymphoma, nodal marginal zone lymphoma and follicular lymphoma. These types of lymphoma have a broad range of survival times, and all require a biopsy sample for diagnosis.   

One of the challenges veterinary oncologists face is the lack of significant cases of a specific lymphoma subtype. For example, splenic marginal zone lymphoma is a rare type of lymphoma. There are fewer than 100 reported cases of this type of lymphoma, but these patients have an excellent long-term prognosis. However, it requires many more diagnoses for veterinarians to feel secure when discussing prognosis with a concerned pet owner.  

Treatment and Outcomes  

Once a veterinarian diagnoses lymphoma, they can begin treatment. Veterinarians treat lymphoma with one of several different chemotherapy protocols tailored to the type of cancer and the patient. Although many dog owners are understandably worried about chemotherapy, most dogs tolerate it exceptionally well and maintain an excellent quality of life during treatment.  

The good news is that complete remission is achieved in 80% to 90% of dogs with an average survival time of 10 to 12 months, and 20% to 25% of dogs will live to two years. Without treatment, dogs live only four to six weeks on average.  

What Can the Golden Retriever Lifetime Study Tell Us About Lymphoma?  

The Golden Retriever Lifetime Study is a unique opportunity to study lymphoma prospectively, in real-time. When the Study began 13 years ago, researchers identified lymphoma as a cancer of particular interest.    

Fast-forward to today, where, as of March 1, 2024, 180 dogs have been diagnosed with lymphoma. Many of these dogs have had their lymphoma subtyped, and we’ve found 47 total B-cell lymphoma types and 82 T-cell lymphoma types, with a few miscellaneous types of lymphoma. Our Study team is working with several research teams to dive deeply into this unique dataset. We hope to find more answers about this common cancer (learn more about the top 5 cancers affecting our Study cohort).

New Studies Bring Hope  

The Foundation has a few new lymphoma studies that will significantly impact dogs diagnosed with this severe disease.  

Two research groups are using Golden Retriever Lifetime Study samples to develop a new early detection test for lymphoma. Each team takes a different approach to the problem, and if successful, the results could significantly impact diagnosis and treatment.   

Another team is harnessing the power of machine learning to help detect if any cancer cells remain after chemotherapy, a situation known as minimal residual disease. Even a tiny amount of cancer cells left behind increases the risk of disease relapse. Having a way to measure treatment success can help optimize therapy.   

These are just a few of the latest studies funded by the Foundation. We can’t wait to see what these researchers can do to help dogs diagnosed with lymphoma.   

Science to Save Animals  

Cancer is a leading cause of death in adult dogs. Veterinarians have limited treatment options due to a lack of research on dog cancers. The truth is that canine cancer research is woefully underfunded.     

The Foundation is working to change this dynamic. Since 1988, the Foundation has funded 52 lymphoma studies and invested just over $4.2 million in grants focused on lymphoma in dogs.  And that doesn’t count the $32 million raised to support the Golden Retriever Lifetime Study!   

We’re committed to learning more about this devastating cancer that touches thousands of dogs and their families each year.    

We know that diagnosing, preventing, treating and possibly even curing cancer starts with science, and science starts with YOU.    

Our Stop Cancer Furever campaign runs from May 1, 2024, through June 30; we’ll be working hard to raise awareness and funds for research aimed at helping stop cancer from taking more lives too soon. And thanks to a generous matching gift provided by Petco Love and Blue Buffalo, your donation can be doubled, up to a total of $100,000, through June 30, 2024.  

With your help, we can improve the odds for dogs with lymphoma and Stop Cancer Furever!   

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