Lymphoma in Dogs and Cats

Understanding lymphoma is the first step to helping you cope with your pet’s diagnosis. An informed owner is key to helping all pets receive the best care available.

Lymphoma is a cancer of the blood and lymph tissue. Lymphocytes, when healthy, produce the antibodies that work to eliminate the body of foreign invaders like allergens and infection-causing germs. Because lymphocytes circulate in the blood stream, which allows blood to flow all over the body, lymphoma exists throughout the body and is thus considered a systemic disease as opposed to a localized disease, which would exist in just one area of the body. Instead of taking over the whole body at once lymphoma tends to primarily localize in only a few body systems at a time, such as the lymph nodes or the intestines. 

How is your pet affected by lymphoma? The rapidly reproducing lymphoma cells invade and interfere with the function of the affected organs and can affect any part of the body. Gastrointestinal (GI or digestive track) involvement is the most common form of lymphoma in cats whereas most dogs are diagnosed with peripheral lymphadenopathy, which means the lymphoma primarily affects the lymph nodes: Over half of the dogs with this diagnosis have lymphoma in their peripheral lymph nodes, the lymph nodes found externally or in extremities. Less commonly, lymphoma will occur in other organs such as chest cavity, intestines, skin, or other organs. Lymphoma may also present with kidney, eye, or central nervous (brain and spinal cord) involvement. In many cases of canine lymphoma, patients are asymptomatic with the exception of enlarged lymph nodes, in contrast to cats who often present clinical signs such as vomiting diarrhea and weight loss.

Lymphoma is one of the most common blood-related diseases in cats. Lymphoma is often related infection or previous exposure to the feline leukemia virus. FeLV positive cats with lymphoma tend to be younger: less than 5 years old.

No one is certain the cause of lymphoma in dogs but recent studies have shown that specific changes in a dogs DNA have been associated with specific subtypes of lymphoma.

It is not common for lymphoma to invade and destroy bone, however, lymphoma accounts for only 5% of primary bone tumors. When lymphoma involves bone, it usually occurs as a result of wide-spread disease. In one study, only 1 of 12 cats had bone involvement where the lymphoma was a singular lesion. Another study suggests that 50% of all so-called singular lesions have lymphoma elsewhere. In two other studies, only 3 of 93 bone tumors, and 1 of 58 bone tumors were caused by lymphoma.

Signs and Symptoms of Lymphoma

Symptoms vary depending on the location and extent of tumor involvement.  For most pets, lymphoma is not painful. In fact, many pets with lymphoma are taken to their veterinarian because the owner feels lumps under the skin in the area of the lymph nodes: under the chin, in front of the shoulders, or behind the knees. Acute limb swelling is also possible. Some pets will have other non-specific signs such as decreased appetite, vomiting, or a sluggish activity level. Of course, since you are the one who spends the most time with your pet, don’t underestimate your intuition as an owner and be diligent about assuming your role as your pet’s advocate if you feel that something is “off.”

Pets with intestinal lymphoma generally experience vomiting and/or diarrhea, along with weight loss. Lymphoma in the chest cavity may cause a cough or intolerance of exercise. Lymphoma of the skin can occur as a single, or as multiple, nodules. Some dogs with lymphoma will have an increased thirst and increased urination because of an elevated blood calcium level. Signs similar to the flu are also frequently present. As the condition progresses signs will worsen.

Whenever your pet is showing signs of a health issue your first step is to contact your primary care veterinarian. If it is indicated that your pet may suffer from lymphoma or another serious condition, a veterinary specialist is available at an ExpertVet certified hospital.