Lymphoma In Dogs: Types, Causes, Symptoms, And Treatments

TO GO WITH AFP STORY BY ISABELLE TOUSSAINT - A dog is treated for cancer at the Eiffelvet veterinary clinic on 22 September, 2014 in Paris. AFP PHOTO / LIONEL BONAVENTURE (Photo credit should read LIONEL BONAVENTURE/AFP/Getty Images)

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Lymphoma is a form of cancer in dogs that affects the lymphocytes, which are white blood cells that are important for immune system function. It is one of the most common malignant tumors in canines, and is usually found in the lymph nodes, the spleen, or the bone marrow, which is where lymphocytes are most concentrated, though it can appear in any organ of the body. Lymphoma can be deadly for dogs if left untreated. Here is what you should know about the types, causes, symptoms, and treatments for lymphoma.

Types Of Lymphoma In Dogs

NEWMARKET, ON - MAY 15: Six-year-old chocolate Labrador Retriever, Oliver, is given chemotherapy during visit at 404 Veterinary Referral Hospital in Newmarket. An overview of veterinary care in Canada which kicks off a series of stories by various reporters on such issues as cancer and pet insurance. (Andrew Francis Wallace/Toronto Star via Getty Images)

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“Lymphoma” is a term that covers more than 30 types of cancer in dogs that each have different mortality rates, symptoms, and levels of aggressiveness. There are four types of lymphoma, however, that are most common.

  • Multicentric lymphoma is the most common type of lymphoma, and makes up 80 to 85 percent of lymphoma cases in dogs. It mostly affects the lymph nodes where you might expect to see swelling.
  • Alimentary lymphoma is the second most common type. It affects the intestines, which is where you can expect to see the strongest symptoms.
  • Mediastinal lymphoma is more rare and affects the thymus and the mediastinal lymph nodes, which are in the chest. You might see enlargement in that area.
  • Extranodal lymphoma affects a specific organ. It can be the skin, kidneys, lungs, central nervous system, or other organs. Most often it affects the skin. This is called a cutaneous lymphoma.

Lymphoma is also designated by stage based on how it has metastasized and how invasive it is. The stages are as follows.

  • Stage I happens when lymphoma only affects one lymph node.
  • State II is regional lymphadenopathy, which means it only affects one side of the diaphragm.
  • Stage III is generalized lymphadenopathy, which happens when the lymph nodes are enlarged.
  • Stage IV is when you see enlargement of the liver or spleen.
  • Stage V is when the lymphoma affects the bone marrow, central nervous system, or other sites beyond the lymph nodes.

Causes Of Lymphoma In Dogs

Richard Finn greets his dog Jason who is ready to go home following two weeks at VCA West Los Angeles Animal Hospital for a bone marrow transplant. Jason was diagnosed with lymphoma and had undergone chemotherapy to put the cancer into remission. The expensive bone marrow transplant was the best hope for permanently eliminating the cancer cells although the success rate is 40-50 percent. (Photo by Myung J. Chun/Los Angeles Times via Getty Images)

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The exact causes of lymphoma in dogs are unknown, but there are certain factors that put dogs more at risk for developing the condition. Dogs with compromised immune systems are more prone to developing lymphoma. Dogs that are exposed to herbicides and those that live in industrial areas are also at greater risk. Additionally, dogs that are exposed to toxic chemicals like paint and solvents show a greater predisposition.

Breed can also affect the likelihood of developing lymphoma. Airedale terriers, Basset Hounds, Boxers, Bulldogs, Golden Retrievers, Scottish terriers, and Saint Bernards are at increased risk for developing the condition. Dog breeds at lower risk include Dachshunds and Pomerians.

Symptoms Of Lymphoma In Dogs

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Symptoms of lymphoma in dogs vary and are generally related to where the tumor forms. Tumors in the lymph nodes may appear as swelling with no other apparent symptoms. Tumors in the gastrointestinal tract may cause symptoms like vomiting, diarrhea, weight loss, and lack of appetite. Lymphoma in the chest may result in shortness of breath or a weak heart beat. Forms of lymphoma that appear on the skin can result in bumps that may be itchy, red, or ulcerated. Here are a few of the symptoms associated with the most common types of lymphoma.

  • Multicentric lymphoma usually appears in the form of swollen lymph nodes. They can appear to be three to ten times their normal size, though they are not painful. The lymph nodes will feel firm to the touch and move freely beneath the skin. The dog may also feel lethargic and weak, lose its appetite, and experience dehydration or a fever.
  • Alimentary lymphoma may cause vomiting, abdominal pain, diarrhea, anorexia, and weight loss.
  • Mediastinal lymphoma results in difficulty breathing, urination, increased thirst, and swelling in the face or front legs.
  • Extranodal lymphoma symptoms vary based on the affected organ. Cutaneous lymphoma that affects the skin results in raised nodules or lesions that can appear on the mouth, lips, and gums. When it appears in the lungs, it causes respiratory issues. In the kidneys it causes renal failure, and in the eyes it causes blindness. In the central nervous system, it can cause seizures, and in the bones it can lead to pain and fractures.

Treatments For Lymphoma In Dogs

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The main treatment for lymphoma in dogs consists of chemotherapy. There is a wide variety of drugs that are used for this purpose, and they can be given orally, or they may be given by injection. Common drugs that treat lymphoma are cyclophosphamide, vincristine, doxorubicin, and prednisone. Radiotherapy may also be used. In some cases, a bone marrow transplant or other surgery may be attempted.

The life expectancy for a dog with lymphoma that is at Stages III through V is about four to six weeks, and drugs are not likely to prolong their lifespan. They can, however, be given medication to reduce swelling and improve their quality of life at the end.

For dogs that go through chemotherapy, their lifespan can typically be extended for a bout a year. It is important to note that there is no cure for the disease, and relapse is very likely. The condition is almost certainly fatal. The goal of treatment is typically to improve quality of life.

A great  and highly informative book on cancer in pets and humans is Pointing The Bone At Cancer by Dr. Ian Billinghurst. A must read for anyone with a pet or loved one suffering from cancer.