Lymphoma (also called lymphosarcoma or LSA) is a cancer that is caused by the uncontrolled growth of lymphoblasts, an immature form of a type of white blood cell. Lymphoma is very common. It affects dogs of any sex, breed, or age, although pets are at highest risk when they are middle aged or older.
Types and Symptoms of Lymphoma
Lymphoma can develop almost anywhere in the body. The most common form of lymphoma, representing over 80% of cases, occurs when cancerous lymphoblasts invade lymph nodes and sometimes the liver, spleen, and bone marrow. This is called multicentric lymphoma. Lymphoma also may be found in the gastrointestinal tract, skin, thymus, mouth, central nervous system, eyes, kidneys, and heart.
The symptoms of lymphoma depend on where the disease is located. Many dogs with multicentric lymphoma seem to feel just fine during the early stages of the disease. They often have no clinical signs other than enlarged, non-painful lymph nodes that owners most frequently find under the jaw, in front of the shoulder blades, or behind the knees. As the disease progresses, however, dogs do develop more general signs of illness like fever, weight loss, lethargy, and loss of appetite.
When lymphoma affects the digestive tract, vomiting, diarrhea, decreased appetite, and weight loss are the most common symptoms. When organs within the chest are involved, difficult or rapid breathing may be seen. Lymphoma of the skin can cause patchy hair loss, flakiness, redness, ulcers, itchiness, and masses within the skin.
A veterinarian may suspect lymphoma based simply on a physical exam, but the diagnosis needs to be confirmed with diagnostic tests. The simplest method is to use a needle to remove cells from within a lymph node and then examine them under the microscope. If the diagnosis is still not clear, a veterinarian may recommend a biopsy or other tests before coming to a final conclusion. Doctors also use blood work, urinalysis, X-rays, ultrasounds, and bone marrow aspirates to determine where else in the body the cancer is located and to determine whether a dog is in good health otherwise. This information can affect a dog’s prognosis and expected response to treatment.
Treatment and Prognosis
Without treatment, most dogs with lymphoma survive for about four to eight weeks after diagnosis, but a variety of therapeutic options are available that will fit almost any situation. The foundation of lymphoma treatment is chemotherapy, but surgery or radiation therapy may also be useful in some instances.
Chemotherapy protocols that make use of several different drugs given over the course of weeks to months bring about remissions for the vast majority of dogs. Dogs are typically “disease free” for several months to about a year, but some do significantly better or worse than average. For owners that do not want to pursue aggressive chemotherapy, treatment with oral prednisone alone can greatly improve a dog’s quality of life, although not necessarily his survival time.
Many people are worried that chemotherapy will make their dogs feel sick, but in fact this does not occur very often. Most canine chemotherapy patients continue to eat, be active, and only rarely experience gastrointestinal upset or significant hair loss.
Nutrition also plays a role in treating lymphoma. Diets that are relatively low in carbohydrates but high in protein, fat, and essential fatty acids are usually best.
Even with aggressive treatment for lymphoma, most dogs eventually experience a relapse. Some patients can be put back into remission with additional chemotherapy, but often this remission is relatively short in duration. Euthanasia and/or hospice care should be considered when a dog’s quality of life is poor and he no longer responds to treatment.