Has your dog been diagnosed with lymphoma or are you concerned that your dog may have lymphoma? Lymphoma in dogs is a cancer of the lymph nodes and is one of the most common types of cancer in dogs. There is no known cause for lymphoma in dogs, but it is believed to be caused by a combination of environmental and genetic factors. Treatment options range from surgery to chemotherapy and radiation therapy. While lymphoma can be a serious disease, with early detection and treatment, dogs can live long happy lives. Early detection is key to treating this disease. To learn more about lymphoma in dogs, please continue reading!

What is lymphoma in dogs?

Lymphoma in dogs is a type of neoplastic cancer that develops in the lymph nodes. The lymph nodes are part of the lymphatic immune system, which is responsible for protecting your dog's body from a variety of infections. Lymphoma can also develop in other organs of the lymphatic system, such as the spleen or bone marrow but the lymph nodes are the most common site in affected dogs. Lymphoma is one of the most common types of cancer in dogs and it usually affects middle-aged to older dogs. There are a variety of breeds susceptible but the Golden Retriever is the most commonly affected breed.

Generally speaking, there are two types of lymphoma in dogs. B cell lymphoma arises from B lymphocytes, which are antibody-producing cells in the humoral immune system. T-cell lymphoma is derived from T lymphocytes (e.g., helper T cells, cytotoxic T cells), which are part of the cell-mediated immune system. Dogs diagnosed with B cell lymphoma generally have a better prognosis than those dogs diagnosed with T cell lymphoma.

What are the causes of lymphoma in dogs?

The underlying cause of lymphoma in dogs is poorly understood. Possible contributing factors include genetics, environmental, and immunologic conditions. There is ongoing research into these factors.

Breeds with predispositions suggest that there may be a genetic component to lymphoma. Living near incinerators, radioactive waste, pollution sites, or industrial areas has been linked to lymphoma in dogs. Researchers found an increased risk in households where pesticide lawn care products were applied professionally. Another study showed the use of paint or solvents by owners has been linked to an increased risk of lymphoma in dogs.

old springer spaniel

Symptoms of lymphoma in dogs

For dogs, lymph nodes are the most commonly affected site. Therefore, the symptoms of lymphoma in dogs include:

  • Generalized lymphadenopathy (enlarged lymph nodes) is one of the most common symptoms of lymphoma in dogs and in some dogs, this is the only symptom. Lymphoma occurs when the cells of the lymph nodes begin to grow uncontrollably. The most noticeable lymph nodes include the submandibular and prescapular (lymph nodes in the neck region), axillary (armpit region), and popliteal (behind the knee region). The enlarged lymph nodes can be quite pronounced and are typically non-painful.
  • Anorexia
  • Weight loss
  • Lethargy
  • Fever
  • Increased thirst and urination (polyuria and polydipsia)

How is lymphoma in dogs diagnosed?

A lymphoma diagnosis is based on a combination of your dog's history, clinical signs, and laboratory testing. A lymphoma diagnosis is typically made with a fine needle aspirate (FNA) of an enlarged lymph node. This involves removing a small cellular sample of the lymph node for evaluation under the microscope. A surgical lymph node biopsy will also help to determine the type of lymphoma present.

microscope 1

Other baseline diagnostic tests that may be performed include:

Complete blood cell count (CBC) - an increase in lymphocytes (a type of white blood cell) is often seen with lymphoma. Anemia can also be present (red blood cell count is low).

Biochemical profile - this blood test evaluates the organs and metabolic system. It may be normal or show abnormalities depending on the type of lymphoma present.

Urinalysis - Urinalysis is a helpful way to assess kidney function and rule out any hidden urinary tract infections before starting immunosuppressive chemotherapy.

Tests to stage lymphoma in dogs

Testing to see how far cancer has spread (staging) can help us determine the best way to treat your dog's lymphoma and give a better idea of how well they might respond to treatment. Treatment for lymphoma in dogs usually involves system-wide therapy, so staging tests rarely change our initial approach, especially if the baseline tests are normal. However, in some cases, full staging may not be necessary, especially if the cost and invasiveness of the tests are taken into account.

Abdominal ultrasound - lymphoma can also affect lymph nodes in the abdomen and the spleen is another common site for lymphoma to spread. This test is necessary for tumor staging purposes.

Thoracic X-rays - lymphoma can also involve lymph nodes in the chest cavity so chest X-rays must be performed. This will also help stage lymphoma in dogs.

Bone marrow biopsy - this test can identify lymphoma cancer cells in the bone marrow which typically occurs in late-stage forms of the disease.

What are the stages of lymphoma in dogs?

Staging classifies lymphoma by the extent of the disease.

Stage I - lymphoma cancer cells only affect one lymph node

Stage II - involves multiple lymph nodes in close proximity

Stage III - represents generalized lymph node involvement and enlargement

Stage IV - lymphoma involves the spleen and/or liver

Stage V - involves the CNS (central nervous system) or bone marrow

Paraneoplastic syndromes secondary to lymphoma in dogs

Paraneoplastic syndromes are conditions that occur as a result of lymphoma but are not directly caused by the cancer cells themselves. Paraneoplastic syndromes can be caused by hormones or other substances secreted by the lymphoma cells or by the body's response to the presence of lymphoma. Anemia (low red blood cell numbers), hypercalcemia (elevated blood calcium levels), hypoglycemia (low blood glucose levels), and thrombocytopenia (low platelet counts) are examples of paraneoplastic syndromes secondary to lymphoma in dogs.

old golden retriever

What are the treatment options for lymphoma in dogs?

The most common treatment for lymphoma in dogs is chemotherapy as it is a systemic disease. Chemotherapy drugs work by killing rapidly dividing cells, which include cancer cells. The goal of chemotherapy is to induce remission, which means that all signs of lymphoma have disappeared.

Chemotherapy protocols

The type of chemotherapy drugs used, the frequency of treatments, and the length of treatment will depend on the type of lymphoma present and the stage of the disease. Chemotherapy is typically given as an outpatient procedure, which means your dog can go home the same day.

The two most common chemotherapy protocols used to treat lymphoma in dogs include:

1. CHOP protocols include 4 different types of medications and they are generally considered the most effective protocols for lymphoma in dogs.

2. University Wisconsin- Madison (UW-25) protocol is a 25-week program to treat lymphoma in dogs.

Corticosteroids

Prednisone can directly kill lymphoma cancer cells and may result in short-term remission. However, it does not have a significant impact on survival time compared to no treatment but prednisone can help reduce symptoms and improve the quality of life for patients with lymphoma cancer. Prednisone is typically started at a high dose for the first few weeks, then the dose is slowly tapered.

Tanovea® (rabacfosadine)

Tanovea® is the newest anti-neoplastic drug FDA-approved for the treatment of lymphoma in dogs. Tanovea® was designed to specifically target and attack cancer cells implicated in lymphoma. The drug is given as an intravenous injection every 3 weeks for up to 5 doses. The data from studies show that Tanovea® is highly effective against lymphoma in dogs, with a 60–80% overall response rate.

What is the prognosis for lymphoma in dogs?

The prognosis for lymphoma in dogs depends on the stage of disease, the type of lymphoma present, and the response to treatment. With early diagnosis and treatment, the prognosis is good for dogs with lymphoma. The median survival time for dogs with lymphoma treated with chemotherapy is 12-14 months. However, some dogs may only live for a few weeks or months after diagnosis while others may go into remission and live for several years.

Can lymphoma in dogs be cured?

While lymphoma can be put into remission, it is considered incurable and has the potential to recur. The average time to recurrence after achieving remission is 6-12 months. For dogs that achieve long-term remission, the median survival time is 2-3 years but these times can vary greatly.

How can I prevent lymphoma in dogs?

There is no known prevention for lymphoma in dogs. However, early detection and treatment are key to giving your dog the best chance for a positive outcome. It's a good idea however to minimize exposure to chemical and environmental pollutants.

In conclusion, lymphoma in dogs is a type of cancer that affects lymph nodes. It is a systemic disease, which means that it can spread throughout the body. The cause of lymphoma in dogs is largely unknown, but it is thought to be related to genetics and exposure to environmental toxins. Chemotherapy is the most common treatment for lymphoma in dogs and the goal of treatment is to induce remission. The prognosis for lymphoma in dogs depends on the stage of disease, the type of lymphoma present, and the response to treatment. With early diagnosis and treatment, the prognosis is can be good for dogs with lymphoma. The median survival time for dogs with lymphoma treated with chemotherapy is 12-14 months. However, some dogs may only live for a few weeks or months after diagnosis while others may go into remission and live for several years.