Lymphoma is a cancer that affects a dog's lymphatic system and causes enlarged lymph nodes, among other organ damage. The primary symptom of lymphoma is swollen lymph nodes, but depending on the type of lymphoma, symptoms may manifest differently. There is no known single cause of lymphoma, but carcinogen exposure, electromagnetic exposure, and genetic predisposition are at play. Breeds like golden retrievers, German shepards, Dobermans, rottweiler, boxer, and Bernese mountain dogs are more likely to develop lymphoma than other breeds. The most effective treatment is usually chemotherapy, but the prognosis for dogs with lymphoma depends on the severity of the cancer.
What Is Lymphoma?
Lymphoma is cancer of the lymphatic system caused by the out-of-control growth of lymphocyte cells. Lymphoma is most commonly found in bone marrow, thymus, lymph nodes, and spleen. The most common forms of lymphoma in dogs are multicentric lymphoma, alimentary lymphoma, mediastinal lymphoma, and extranodal lymphoma. Lymphoma can be acute and local to its initially affected area in the body or spread to other organs. The most palpable lymph nodes are under the jaw, behind the knee, in the groin, in the armpit, and front of the shoulder.
Symptoms of Lymphoma in Dogs
Lymphoma in dogs will usually present as an enlarged lymph node but can also cause other symptoms. If you notice swelling in your dog, visit your vet right away.
The most common and noticeable symptom of lymphoma in dogs is a swollen lymph node. Usually, the enlarged lymph node is firm and non-painful to the touch. Dogs with lymphoma in the early stages don't always exhibit symptoms besides their swollen lymph nodes. Still, lymphoma may manifest in other symptoms like vomiting, fever, lethargy, weight loss, and more as the cancer progresses. Symptoms also depend on your dog's type of lymphoma. Alimentary lymphoma, for example, will cause your dog to display gastrointestinal symptoms, while extranodal lymphoma will cause your dog to display irritation on its skin.
Causes of Lymphoma
The causes of lymphoma are not entirely understood, but there are a variety of factors that contribute to the development of the disease.
- Chemical exposure: Exposure to carcinogenic chemicals heightens the risk of lymphoma in dogs. There is a link between certain lawn care and pesticide products and the development of lymphoma in dogs. Additionally, lymphoma has been associated with dogs who live within two miles of a chemical supplier or a crematorium.
- Genetics: Genetic mutations are thought to contribute to lymphoma in dogs, but origins of the mutations are unknown. Lymphoma is more common in some breeds than others. Some studies find that golden retrievers, German shepards, Dobermans, rottweiler, boxer, and Bernese mountain dogs are particularly susceptible to developing lymphoma.
- Bacteria and viruses: Some viruses and bacteria have been linked to the development of lymphoma in dogs, but not much is known as how to they trigger lymphoma. Epstein Barr virus and Epstein Barr-like viruses, for example, cause excessive growth of B cells, which can contribute to the development of lymphoma.
- Magnetic field exposure: Electromagnetic fields, like x-rays or areas of high electricity output, can contribute to the development of lymphoma in dogs.
- Age: Older dogs are at higher risk of developing lymphoma. Dogs between the ages of eight and eleven are more likely to develop lymphoma than younger dogs, but all dogs can develop the disease regardless of age.
Diagnosing Lymphoma in Dogs
Your vet will perform a complete physical examination to diagnose lymphoma, palpating vulnerable areas on your dog. If your vet notices a swollen lymph node, they will conduct a fine-needle aspiration or biopsy and observe the sample under a microscope. Usually, a biopsy alone is enough to diagnose lymphoma. After your vet detects lymphoma, they may perform blood analysis, urinalysis, x-ray, or ultrasound to assess the extent of the cancer's effect on your dog and determine the cancer's stage.
After your dog's lymphoma is staged, you will have a consultation with an oncologist, where they will review your dog's health aside from the lymphoma and determine an appropriate treatment plan. Chemotherapy is usually highly effective in treating lymphoma in dogs. Dogs tend to tolerate chemotherapy well, but side effects like nausea, anorexia, and gastrointestinal distress can occur. Your vet may also recommend radiation therapy, bone marrow transplant, and steroids.
Prognosis for Dogs With Lymphoma
The prognosis for dogs with lymphoma depends on the cancer stage and the success of the chemotherapy. Dogs with lymphoma that have been diagnosed and treated early have a good prognosis and usually survive for at least two years. While chemotherapy has a high success rate, most dogs will relapse. Survival times will vary, but with chemotherapy treatment, where dogs achieve complete remission, dogs have an average survival time of 12 to 14 months. Without treatment, the life expectancy in dogs with lymphoma is one to two months.
How To Prevent Lymphoma
You cannot entirely prevent your dog from developing lymphoma, but there are preventative measures you can take to minimize the risk. Keep your dog away from carcinogens like smoke, and be careful not to use cancer-causing chemicals and pesticides. Pay attention to any changes in your dog's body to detect lymphoma early if it does occur. Make sure your dog lives a healthy lifestyle overall and maintains a healthy weight.
Types of Lymphoma in Dogs
- Multicentric lymphoma: Multicentric lymphoma accounts for most lymphoma cases in dogs. Multicentric lymphoma is systemic and involves cancer of multiple lymph nodes and sometimes other organs.
- Extranodal lymphoma: Extranodal lymphoma affects a specific organ outside the lymphatic system.
- Mediastinal lymphoma: Mediastinal lymphoma primarily affects lymph nodes related to a dog's chest. Dogs with mediastinal lymphoma may have difficulty breathing.
- Alimentary lymphoma: Alimentary lymphoma is relatively rare. It affects the gastrointestinal tract and usually presents symptoms like diarrhea, vomiting, and loss of appetite.
Can chemical exposure cause lymphoma in my dog?
Some lawn-care products and pesticides can contribute to lymphoma in dogs. Before buying any household chemical, research its toxicity.
Can you prevent lymphoma in dogs?
Lymphoma cannot be entirely prevented, but keeping your dog away from carcinogenic chemicals and maintaining a healthy lifestyle can help minimize risk.
Will my dog survive lymphoma?
The survival time of a dog with lymphoma is dependent on the severity of the cancer and your dog's response to treatment. Cases caught early have a higher survival rate than cases detected late.
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Exposure to Environmental Chemicals in Boxers with Lymphoma. AKC.
Comazzi, S. et al. Breed-Associated Risks for Developing Canine Lymphoma Differ Among Countries: An European Canine Lymphoma Network Study. BMC veterinary research, 14(1), 232, 2018. doi:10.1186/s12917-018-1557-2
Epstein Barr-like Virus Infects and May Cause Cancer in Dogs. Science Daily.
Canine Lymphoma. AKC.