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You’re likely familiar with the term lymphoma, a fairly well-known type of cancer that affects many people, especially at younger ages. Unfortunately, our canine companions are also susceptible to this life-threatening cancer. In fact, it’s one of the most common types of cancer in dogs.
In our furry friends, lymphoma can develop with minimal or no initial symptoms of illness, yet some forms can spread aggressively if not caught early. We’ll help you learn how to spot early signs, most commonly enlarged lymph nodes, and everything else you should know about this serious disease.
What Is Lymphoma?
Veterinarians use the term malignant lymphoma to describe a group of cancers of the lymph nodes and lymphatic system, a network of lymph vessels, tissues, and organs throughout the body. Lymphoma in dogs is quite similar to the commonly occurring non-Hodgkin’s lymphoma in humans.
Lymphoma is caused by the abnormal growth of lymphocytes. Lymphocytes are a type of white blood cell that’s instrumental in the immune system’s ability to fight off various diseases and infections. These cells are highly concentrated in the lymph nodes, spleen, and bone marrow, where most lymphomas develop. The majority of lymphomas are high-grade (also called large-cell lymphoma) and rapidly progress.
What Causes Lymphoma In Dogs?
Unfortunately, we don’t know what causes the abnormal growth of lymphocytes in dogs. Despite studies into possible causes (e.g., chemical exposure, bacteria, viruses, etc.), certain evidence of a cause remains inconclusive. Therefore, there’s currently no way to prevent lymphoma in dogs.
In humans, scientists have found evidence that suppression of the immune system is a known risk factor for lymphoma. Humans infected with HIV or those on immune-suppressing drugs following organ transplant surgery have increased rates of lymphoma. However, the link between immune suppression and lymphoma in dogs hasn’t been established, according to Purdue University’s College of Veterinary Medicine.
How Common Is Lymphoma In Dogs?
Lymphoma is among the most common cancer in dogs, accounting for approximately 10-20% of all dog cancers. It typically affects middle-aged and older dogs, and genetics appear to play a factor. Breeds predisposed to lymphoma include Airedale Terriers, Basset Hounds, Boxers, Bulldogs, Bullmastiffs, Golden Retrievers, Labrador Retrievers, Saint Bernards, and Scottish Terriers.
Types Of Lymphoma Cancer In Dogs
There are more than 30 different types of lymphoma, but the following account for a vast majority of lymphoma cases in dogs.
- Multicentric lymphoma: By far the most common form, multicentric lymphoma accounts for about 80%-85% of cases of lymphoma in dogs. This type affects lymph nodes throughout the body.
- Alimentary lymphoma (or gastrointestinal lymphoma): The second most common lymphoma in dogs, it affects the intestines and/or the stomach. However, it accounts for less than 10% of cases.
- Mediastinal lymphoma: Much less common, this lymphoma involves organs within the chest, such as the thymus gland or lymph nodes.
- Extranodal lymphoma: This form of lymphoma develops in organs outside of the lymphatic system. While rare, extranodal lymphoma can attack the eyes, lungs, kidneys, skin, bones, or nervous system.
- Cutaneous lymphoma: The most common extranodal form, cutaneous lymphoma affects the skin. However, these cases are rare, accounting for only 5% of lymphomas in dogs.
Symptoms Of Lymphoma In Dogs
The first and most obvious sign of multicentric lymphoma, the most common form of this cancer, is swollen lymph nodes in dogs. They feel like hard, rubbery lumps under your pup’s skin. Lymph nodes located in the neck under the jaw and behind the knees are the easiest to detect swelling. Many dogs don’t show signs of illness at first but over time can develop other symptoms.
- Swollen lymph nodes
- Decreased appetite
- Weight loss
- Facial or leg swelling
- Increased thirst and urination
In the much less common types of lymphoma, signs depend on the affected organ. These and other rare forms of the disease only represent 15%-20% of all lymphoma cases in dogs.
- Gastrointestinal (alimentary) lymphoma can cause watery, dark, foul-smelling diarrhea, vomiting, and weight loss.
- Mediastinal lymphoma usually results in breathing problems and coughing.
- Cutaneous lymphoma appears as thickened lumps or dry, scaly, red, areas of skin anywhere on the body or in the mouth. As it progresses, these patches become moist, ulcerated, and extremely red.
- Other extranodal lymphomas can cause respiratory distress, kidney failure, blindness, seizures, or bone fractures and pain, depending on the affected organ.
Where Are My Dog’s Lymph Nodes? (Video)
Because many dogs with lymphoma show minor to no signs of being ill, it can be helpful to check your furry friend’s lymph nodes regularly for any swelling. In the video below, a veterinary oncologist shows you exactly where to find all of your dog’s lymph nodes.
How Is Lymphoma Diagnosed?
Canine lymphoma is often fairly easy for veterinarians to diagnose by taking a small tissue or cell sample from the affected organ. Most likely, your vet will do a fine-needle aspiration, which extracts a sample from your dog’s lymph nodes or other affected organs. In some cases, a surgical biopsy may be recommended. Then, the cells are examined to confirm the presence of cancerous lymphoma.
Once lymphoma has been confirmed, veterinarians run specialized tests to distinguish whether your dog has B-cell or T-cell lymphoma (this can help with a prognosis). Some vets also recommend staging tests to determine how far the lymphoma has spread throughout your dog’s body. These additional tests include bloodwork, urinalysis, x-rays of the chest and abdomen, abdominal sonogram, and bone marrow aspiration.
What Are The Stages Of Lymphoma In Dogs?
The results of staging tests help veterinarians develop a personalized treatment plan for your pup. The five stages of canine lymphoma include:
- Stage I: Only one lymph node is affected.
- Stage II: More than one lymph node is affected but they’re only on one side of the body (front or rear).
- Stage III: Multiple nodes are affected in the front and back of the body.
- Stage IV: Lymphoma is present in the spleen and/or liver.
- Stage V: The bone marrow, nervous system, intestines, skin, or other locations are affected.
Lymphoma In Dogs Treatment
Chemotherapy is the standard treatment for lymphoma in dogs and can extend your dog’s life for some time (however, the disease is eventually fatal). Fortunately, dogs typically don’t suffer severe side effects or hair loss from chemotherapy as humans do; although some may experience mild vomiting, diarrhea, lethargy, or loss of appetite. The types of chemotherapy drugs used depend on the type of lymphoma. In some cases, surgery and/or radiation may be recommended.
The treatment protocols that achieve the highest remission and longest survival rates in multicentric lymphoma involve a combination of chemotherapy drugs (IV and oral) given weekly for 25 weeks. This “gold-standard” chemotherapy protocol, UW-25, is based on the CHOP protocol commonly used to treat lymphoma in humans.
What’s The Survival Rate For Dogs With Lymphoma?
Of course, this is one of the most pressing questions pet owners have so we can prepare ourselves for difficult decisions and emotional turmoil. But there’s no easy answer. It can depend on the type and stage of the disease. Without treatment, the life expectancy in dogs with lymphoma is four to six weeks. With chemotherapy, the average survival time is about 12 months. Once your vet has determined the stage of your pup’s cancer, they could be able to give you a clearer prognosis.
Although lymphoma is eventually fatal, chemotherapy could prolong your pup’s life (and at a good quality of life, in many cases), giving you more time with your pup. According to the Merck Veterinary Manual, more than 90% of dogs with multicentric canine lymphoma (the most common form) treated with chemotherapy achieve complete remission. Complete remission means that all symptoms and signs have become undetectable, but cancer could still be lurking in the body.
Unfortunately, with most dogs, lymphoma returns (called a relapse). Further chemotherapy helps many dogs go back into remission, but it usually doesn’t last as long as the first remission. And eventually, most lymphomas develop resistance to all chemotherapy medications.
Does Pet Insurance Cover Cancer?
Diagnosing and treating cancer in dogs is extremely expensive. Treatment costs for lymphoma average $5,000 but can range anywhere from $1,000-10,000. These expenses can be cost-prohibitive for many pet parents. Fortunately, pet insurance does cover cancer, as long you have a policy before your pup becomes ill. If your dog is uninsured, you might consider pet insurance so that you never have to decide between a major financial hit or your dog’s life.
Dealing With End-Of-Life Care
Dealing with a diagnosis of lymphoma is a heart-wrenching experience for pet parents. If you’re currently going through this, we’re sincerely sorry for your news. From our own experiences, we have some information and advice to help you prepare for end-of-life concerns. As your dog’s disease progresses, the main concern is your pup’s deteriorating health.
It’s helpful to know how to assess your furry friend’s quality of life to keep the rest of his time with you as happy, comfortable, and independent as possible. At some point, you may also want to read our article on how to deal with the death of your dog to help you emotionally prepare yourself for other difficult end-of-life decisions and handle the grief you likely are already feeling.