Lymphoma in Dogs: Symptoms, Causes, & Treatments

Canine lymphoma — also known as lymphosarcoma (LSA) — is a type of cancer that originates in the lymphatic system, which is an integral part of a dog’s immune system. It is one of the most common malignant tumors in canines. The lymphatic system includes lymph nodes, the spleen, and other organs involved in the production and circulation of lymphocytes, a type of white blood cell. When a dog develops lymphoma, these lymphocytes multiply uncontrollably, leading to the formation of tumors in various parts of the body.

Here’s what you should know about the types, symptoms, causes, and treatments for the disease.

Types of lymphomas in dogs

There are over 30 different types of canine lymphomas, each with unique characteristics, treatment options, and prognoses. However, the four most common types are:

• Multicentric lymphoma: This is the most common form of lymphoma in dogs, accounting for approximately 80-85% of cases. It primarily affects the lymph nodes, but can also spread to other organs such as the liver, spleen, and bone marrow. Dogs with multicentric lymphoma often present with enlarged — but not necessarily painful — lymph nodes.
• Alimentary lymphoma: Alimentary lymphoma — also known as gastrointestinal lymphoma — affects the gastrointestinal tract and is the second most common type. It can cause significant digestive issues and may lead to severe malnutrition if not promptly treated.
• Mediastinal lymphoma: This type involves the lymphoid organs in the chest, particularly the thymus and the mediastinal lymph nodes. Mediastinal lymphoma is less common and can be challenging to treat.
• Extranodal lymphoma: Extranodal lymphoma targets specific organs outside of the lymphatic system, such as the skin — cutaneous lymphoma — eyes, central nervous system, lungs, or kidneys. Symptoms vary widely depending on the affected organ. For instance, cutaneous lymphoma may present as lesions or nodules on the skin, while central nervous system lymphoma may cause neurological symptoms like seizures or behavioral changes.

Stages of lymphoma in dogs

LSA in dogs is typically classified into five stages based on the extent of the disease and the organs involved. This designation helps veterinarians develop appropriate treatment plans. The staging system most commonly used is based on the World Health Organization (WHO) classification.

• Stage I: At this initial stage, the cancer is localized to a single lymph node or a single organ other than the bone marrow. This is the least severe stage and may present fewer symptoms, making it harder to detect without thorough veterinary examination.
• Stage II: In stage II, multiple lymph nodes are affected, but they are confined to either the front or the back half of the body. This means the lymph nodes involved are either all above or all below the diaphragm. The progression from stage I to stage II often leads to more noticeable symptoms.
• Stage III: This stage is characterized by the involvement of lymph nodes on both sides of the diaphragm. The cancer has spread, but it is still primarily within the lymphatic system. Dogs in stage III often show more pronounced symptoms, including enlarged lymph nodes that can be felt under the skin in various parts of the body.
• Stage IV: By stage IV, the lymphoma has spread beyond the lymph nodes to include the liver and/or spleen. This stage indicates a more aggressive form of the disease and is typically associated with systemic symptoms such as weight loss, lethargy, and possibly jaundice due to liver dysfunction.
• Stage V: Stage V represents the most advanced stage of canine lymphoma. The cancer has spread to the bone marrow and possibly other organs such as the skin, lungs, or kidneys. At this stage, dogs often exhibit severe symptoms related to organ dysfunction, and the prognosis is generally poor.

Symptoms of lymphoma in dogs

One of the first signs of lymphoma in dogs is the enlargement of lymph nodes. These nodes may feel firm and rubbery to the touch and are often found in the neck, under the jaw, behind the knees, and in the armpit area. The swelling is typically painless and may go unnoticed until it becomes quite pronounced.

Dogs with lymphoma may also exhibit other symptoms such as:

• Lethargy
• Weight loss
• Loss of appetite
• Increased thirst and urination

Symptoms can also vary depending on the affected body area. For cutaneous LSA, signs may include red or ulcerated skin lesions, scaly or flaky patches of skin, hair loss in affected areas, changes in skin color, and thickened skin. Gastrointestinal LSA often presents with vomiting and diarrhea, while mediastinal LSA may cause coughing, difficulty breathing, and exercise intolerance.

If you observe any of these signs, it’s crucial to consult your veterinarian as soon as possible. Your vet will likely perform a thorough physical examination, during which they will look for enlarged lymph nodes and other potential signs of the disease. Blood tests, such as a complete blood count (CBC) and serum biochemistry profile, can provide valuable information about your dog’s overall health and help identify abnormalities that may be associated with lymphoma.

In many cases, your vet may recommend additional diagnostic tests to confirm the presence of the disease. These might include a fine needle aspiration (FNA) or biopsy of the affected lymph nodes or organs. Imaging studies, including X-rays, ultrasound, and advanced techniques like CT scans, can also offer more detailed insights into the extent and location of the disease. Once your vet gathers all necessary information, they’ll discuss the diagnosis with you and outline the available treatment options.

Causes of lymphoma in dogs

The exact causes of lymphoma in dogs remain largely unknown, but certain factors put dogs more at risk.

Breeds most susceptible to canine lymphomas

Certain breeds exhibit a higher predisposition to the disease, suggesting a genetic component. These are:

• Boxers
• Bull Mastiffs
• Basset Hounds
• Saint Bernards
• Golden Retrievers
• Scottish Terriers
• Airedale Terriers
• Bulldogs

Potential environmental causes of cancer in dogs

Furthermore, environmental factors like exposure to chemicals, pesticides, and pollutants are suspected to increase the risk. Researchers are also exploring the possibility of viral infections acting as catalysts for the development of canine lymphoma.

Other health factors which may contribute to a diagnosis

Dogs with weakened or compromised immune systems — whether due to autoimmune diseases or prolonged use of immunosuppressive drugs — may be more susceptible to developing the disease. Age is another contributing factor, as the likelihood of lymphoma tends to increase in older dogs.

Treatments for lymphoma in dogs

While a lymphoma diagnosis can be distressing, there are several treatment options available that can help manage the disease and improve your dog’s quality of life. The choice of treatment depends on the type and stage of lymphoma, as well as the overall health of your dog. Here are some of the primary treatments for lymphoma in dogs.

Chemotherapy

Chemotherapy is the most common and effective treatment for canine lymphoma. It involves using a combination of drugs to kill cancer cells and shrink tumors. The most popular chemotherapy protocol for dogs is the CHOP protocol, which includes a combination of Cyclophosphamide, Hydroxydaunorubicin (doxorubicin), Oncovin (vincristine), and Prednisone. These drugs are administered in cycles over several weeks to months. While chemotherapy can have side effects such as nausea, vomiting, and loss of appetite, dogs tend to tolerate it better than humans.

Radiation therapy

Radiation therapy is often used in conjunction with chemotherapy or as a standalone treatment. This treatment involves using high-energy rays to target and kill cancer cells. It’s particularly useful for treating lymphoma in specific locations like the nasal passages or central nervous system. The treatment usually requires multiple sessions over several weeks. Anesthesia is typically needed to keep the dog still during the procedure.

Immunotherapy

Recent advancements in veterinary medicine have led to the development of immunotherapies for canine lymphoma. These treatments aim to enhance the dog’s own immune system to fight the cancer more effectively. One example is the use of monoclonal antibodies that specifically target lymphoma cells, marking them for destruction by the immune system. Although still in the early stages of development, immunotherapy shows promise as a less toxic and more targeted approach to treating lymphoma.

Surgery

Surgery is not typically the first line of treatment for lymphoma since the cancer is usually systemic. However, it may be considered if the lymphoma is confined to a single, accessible lymph node or organ. Surgical removal of the affected tissue can sometimes be followed by chemotherapy to address any remaining cancer cells.

Palliative care

For dogs who are not candidates for aggressive treatments or whose lymphoma has progressed beyond the point where other treatments are effective, palliative care is an option. The goal of palliative care is to manage symptoms and maintain quality of life. This may involve the use of steroids like prednisone to reduce inflammation and swelling, as well as pain management medications and nutritional support.

Prognosis for lymphoma in dogs

The life expectancy of a dog diagnosed with lymphoma can vary significantly based on factors such as the stage of the disease at diagnosis, the specific type of lymphoma, and the chosen treatment plan. Without treatment, the survival time is typically only about one to two months. However, with appropriate treatment, many dogs can achieve remission and experience significantly extended lifespans. For instance, dogs undergoing chemotherapy may live an additional six to 12 months on average. Some may even live for a couple of years or more, depending on how well they respond to the treatment.

Before discussing treatments for canine lymphoma, it is important to bear in mind that there is no cure for the disease, and relapse is very likely due to its aggressive nature. As the cancer returns, it often becomes more resistant to therapies, making subsequent remissions shorter and treatment less effective. In such cases, veterinarians may discuss the option of euthanasia to prevent unnecessary suffering, particularly when quality of life significantly deteriorates or when the disease no longer responds to treatment. If your dog is diagnosed with lymphoma, consult your veterinarian to determine the most appropriate action plan.

Remember, early diagnosis and prompt treatment can significantly improve the prognosis. While there are no guaranteed measures to prevent canine lymphoma, maintaining a healthy lifestyle for your dog — through balanced nutrition, regular vet check-ups, and avoiding exposure to known carcinogens — can contribute to overall well-being and potentially reduce the risk of various diseases, including cancer. It can also ensure a higher quality of life for your pup even if they are diagnosed, and even be a form of supportive care for your dog if they must undergo treatment at any point in time.