Lymphoma in Dogs and Cats

Lymphoma is a very common form of cancer seen in dogs and cats. It arises from the abnormal proliferation of lymphocytes (a type of white blood cell) within different tissues around the body. Lymphoma most commonly occurs in the lymph nodes, the spleen, and the liver, but the disease can involve almost any tissue in the body, which makes the presentation and course of the disease extremely variable.

Lymphoma is most commonly seen in middle-aged dogs and certain breeds are also predisposed to it, such as boxers and golden retrievers. Most dogs who develop lymphoma get a formed called “multicentric” in which several of the lymph nodes become enlarged. Lymphoma will also commonly affect the intestinal tract, liver, spleen, chest, and the skin.

Signs of lymphoma are extremely variable due to the disease’s ability to affect so many different locations around the body. The most common sign is lymph node enlargement, which may feel like lumps growing below the skin. This is often the only sign present, but some animals with lymphoma can also develop weight loss, lethargy, decreased appetite, vomiting, diarrhea, increased drinking/urination, skin lesions, difficulty breathing, facial swelling, or any combination of these signs.

The diagnosis of lymphoma depends on it’s location but it is most often diagnosed by aspirating cells from the affected organs (lymph nodes, spleen, liver) with a small needle and examining the cells under a microscope. In some cases a biopsy is required to make a diagnosis. Based on aspiration or biopsy results the “grade” of the cancer can also be determined, as well as the cell type present (T-cell versus B-cell lymphoma), both of which help us estimate a prognosis for the disease.

Lymphoma is very serious disease and will almost always claim an animal’s life eventually, however with treatment dogs and cats can life a relatively long period of time, with a high quality of life, doing all the normal things that they love. Without treatment the prognosis is only 1-2 months, with treatment the prognosis depends on the type of lymphoma present and the treatment protocol followed. Treatment for lymphoma is individually tailored to each animal, as well as the time and financial constraints of their owner. Chemotherapy in dogs and cats is usually far better tolerated than in people. We use lower doses, in order to maintain quality of life during treatment, and most animals will have minimal side effects.

In general, the treatment protocols for lymphoma that provide the best survival times and the best chance of putting an animal’s disease into remission are multi-drug protocols. With these protocols animals will generally be given a different chemotherapeutic drug every 1-2 weeks for 6 months or longer. Other treatment options include single drug chemotherapy protocols or treatment with steroids alone. These options are less costly than multi-drug protocols but generally the remission times and survival times are not as long.

We understand how scary it is to have a family pet diagnosed with a cancer such as lymphoma, however by working with your veterinarian and local veterinary oncologist lymphoma can be managed to allow you to spend the most quality time possible with your pet.

Trevor Miller, DVM