Lymphoma is a common cancer in people and dogs that affects the lymph nodes and lymphatic system. The lymphatic system is comprised of organs, tissues, and vessels. It is responsible for fighting infection and keeping a healthy level of fluids throughout the body.
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While older dogs tend to be more predisposed to developing cancer, younger dogs can also be at risk. Symptoms and outcomes vary depending on the type and stage of lymphoma, but early understanding can help owners make informed decisions about care and treatment.
What Is Lymphoma in Dogs?
Lymphoma is a general term used to describe a group of cancers that develop from lymphocytes, a type of white blood cell that plays a key role in the immune system. Changes in lymphocyte levels can heavily affect organs like the lymph nodes, the spleen, and bone marrow. Most lymphoma cancers are found in these organs, but lymphoma can affect any organ in the body.
Veterinarians and human doctors use similar chemotherapy protocols to treat lymphoma in dogs and people, and there are also similarities in how lymphoma is diagnosed and classified in each species. However, precursor diseases, which are the presence of abnormal cells that progress to disease and increase the likelihood of illness, are more common in dogs than in people. These precursor diseases are tied to different types of lymphoma in dogs. For example, if they originate from cells in bone marrow, the cancer will involve blood or bone marrow.
Types of Lymphoma in Dogs
There are more than 30 different types of known canine lymphomas, varying in aggressiveness, survival rates, and clinical signs. These differences can make lymphoma difficult to diagnose at first.
The four most common types of lymphoma in dogs are:
- Multicentric lymphoma
- Alimentary lymphoma
- Mediastinal lymphoma
- Extranodal lymphoma
Multicentric Lymphoma
Multicentric lymphoma, which affects the lymph nodes, accounts for approximately 80% to 85% of lymphomas in dogs. In most cases, the most obvious sign for veterinarians is the lymph nodes rapidly getting larger — often growing to three to 10 times their normal size. Lymph nodes are located in different parts of the body, including the neck, chest, armpits, behind the knees, and groin, and any of these areas can be affected.
This swelling isn’t painful and feels like a firm, rubbery lump that moves freely beneath the skin. As the disease progresses, dogs with multicentric lymphoma may also develop symptoms including:
- Lethargy
- Fever
- Anorexia or lack of appetite
- Weakness
- Dehydration
A pilot study found that several types of gut bacteria were present in greater amounts in dogs with multicentric lymphoma. This suggests their presence could potentially act as biomarkers for multicentric lymphoma, which are indicators of what’s going on in a cell at a given time. By recognizing possible biomarkers of multicentric lymphoma, scientists may be able to more effectively track the disease’s progress in the future.
Alimentary Lymphoma
The second most common form of lymphoma is alimentary lymphoma, which accounts for less than 10% of canine lymphomas and targets the intestines, where most symptoms occur. Dogs with alimentary lymphoma may experience symptoms including:
Mediastinal Lymphoma
Mediastinal lymphoma is rare and is named for the mediastinal lymph nodes located in the chest area. This lymphoma can affect these lymph nodes, the thymus (the gland that produces white blood cells), or both, causing them to become enlarged. High-grade malignant T lymphocytes — cells that grow and spread quickly and look abnormal under a microscope — can cause this enlargement.
As the disease progresses, dogs with mediastinal lymphoma may experience shortness of breath. This can happen when fluids accumulate in the chest, creating additional pressure on the lungs and possibly even blocking veins that carry blood away from the heart. Affected dogs may also drink and urinate more frequently when calcium builds up in the blood.
Extranodal Lymphoma
Extranodal lymphoma in dogs refers to lymphoma that targets a specific organ, such as the skin, eyes, kidneys, lungs, or central nervous system. The most common extranodal lymphoma affects the skin and is called cutaneous lymphoma. The symptoms depend on the organs affected. Telltale signs of cutaneous lymphoma are individual, raised nodules or generally dispersed scaly lesions. Cutaneous lymphoma may also affect the gums, lips, and the roof of the mouth.
Symptoms vary further depending on which organ is affected:
- Lungs: respiratory distress
- Kidneys: renal failure
- Eyes: vision loss or blindness
- Central nervous system: seizures
- Bones: pain or fractures
What Causes Lymphoma in Dogs?
Researchers have only recently properly recognized lymphoma as a group of diseases with distinct subtypes. Still, there is a lot we don’t know about what causes lymphoma in dogs. Lymphoma accounts for approximately 7% to 24% of cancers in dogs.
Since dogs share our environment, they’re exposed to many of the same environmental factors that may cause cancer in humans. These include phenoxyacetic acid and toxic substances produced during the breakdown of chemicals, including pesticides, fungicides, medications, and chemical dyes. Researchers suspect that viruses, infections, age, and UV damage are possible contributors to cancer. They suspect the most likely cause is a combination of genetic and environmental factors.
One study took a look at 78 breeds, and out of these, there was an increased risk of lymphoma in 30 dog breeds and a reduced risk in 26 breeds. Results for the remaining breeds weren’t statistically significant. Results suggested that male dogs, whom researchers noted were represented more than female dogs in the study, were more likely to develop lymphoma. Spayed or neutered dogs of both sexes were at higher risk for lymphoma when compared to intact dogs in this study.
There is hope that advanced genetic studies may help identify any underlying genetic and chromosomal causes and predispositions toward lymphoma. Genes can also help to explain why certain breeds are more predisposed to developing lymphoma, including the Golden Retriever, Beagle, Saint Bernard, and Rottweiler.
How Lymphoma Is Diagnosed
Veterinarians often suspect lymphoma after detecting enlarged lymph nodes during a physical exam. To confirm a diagnosis, they collect tissue or cell samples from the affected area. often with fine-needle aspiration. They’ll evaluate this sample through a cytology exam (examining a single type of cell) or by a biopsy (examining a section of tissue).
Following a lymphoma diagnosis, a veterinarian may recommend additional testing to assess how far the disease has progressed. This process, known as staging, can include blood work, urine tests, imaging, and bone marrow aspiration.
Lymphoma is classified into five stages based on how widely it has spread. Early stages involve limited lymph node involvement, while advanced stages may include organs or bone marrow:
- Stage I: Involves a single lymph node
- Stage II: Affects multiple lymph nodes in one region
- Stage III: All lymph nodes affected (generalized)
- Stage IV: Involves lymph nodes and organs such as the liver, spleen, or chest
- Stage V: Involves the bone marrow
Treating Lymphoma in Dogs
Chemotherapy is the most effective and commonly used treatment for canine lymphoma. The type of chemotherapy your vet recommends will vary depending on the type and severity of the disease. In some cases, they may also suggest radiation therapy or surgery.
For instance, dogs with multicentric lymphoma often receive a chemotherapy protocol known as UW-25. UW-25 is based on the CHOP protocol used in humans, which involves using four different drugs that are administered together. When combined, they have a better chance of stopping the growth of cancer. Administering the drug lomustine (also known as CCNU) is considered the chemotherapy protocol that’s most effective for treating cutaneous lymphoma.
Prognosis and Survival Expectations
The outlook for dogs with lymphoma depends on several factors, including the type of cancer, stage at diagnosis, and response to treatment. According to a recent study, many dogs respond well to chemotherapy and achieve remission, meaning the cancer becomes undetectable or significantly reduced.
However, relapse is common and when the cancer returns, it’s often more resistant to treatment, although a second remission is sometimes possible. Unfortunately, lymphoma is generally considered a progressive and ultimately fatal disease.
Living With a Dog With Lymphoma
Caring for a dog with lymphoma involves working closely with a veterinarian to monitor symptoms and adjust treatment as needed. Owners may also consider supportive or hospice care to keep their dog comfortable as the disease advances.
Lymphoma is a complex disease with many different factors that can impact your dog’s health. Being proactive about care and informed about options can improve your dog’s quality of life and help you prepare for changes over time.
Key Takeaways
- Lymphoma is a common canine cancer that affects the lymphatic system and can impact many organs.
- Swollen lymph nodes are often the first noticeable sign, especially in multicentric lymphoma.
- Chemotherapy is the most common treatment and can lead to remission in many dogs.
- The disease is usually progressive, and relapse is common even after successful treatment.
- Early detection and ongoing veterinary care can improve a dog’s quality of life.
Frequently Asked Questions
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What are the first signs of lymphoma in dogs?
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The earliest sign is usually enlarged lymph nodes, especially in the neck, armpits, or behind the knees. Other early symptoms can include lethargy, appetite loss, and mild weight loss.
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Is lymphoma in dogs painful?
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In many cases, especially early on, lymphoma is not painful. However, discomfort can develop later depending on the organs affected and the progression of the disease.
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Can lymphoma in dogs be cured?
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Lymphoma is typically not curable, but many dogs respond well to treatment and can achieve remission for a period of time with improved quality of life.
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How long can a dog live with lymphoma?
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Life expectancy varies widely based on the type of lymphoma, stage, and treatment. Dogs receiving chemotherapy often live longer than untreated dogs.
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What should I do if I suspect lymphoma?
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If you notice unusual swelling, changes in appetite, or other concerning symptoms, consult your veterinarian promptly. Early diagnosis can lead to better management options.
This article is intended solely as general guidance, and does not constitute health or other professional advice. Individual situations and applicable laws vary by jurisdiction, and you are encouraged to obtain appropriate advice from qualified professionals in the applicable jurisdictions. We make no representations or warranties concerning any course of action taken by any person following or otherwise using the information offered or provided in this article, including any such information associated with and provided in connection with third-party products, and we will not be liable for any direct, indirect, consequential, special, exemplary or other damages that may result, including but not limited to economic loss, injury, illness or death.