Lymphosarcoma in Dogs
Forms of Lymphosarcoma (a.k.a. lymphoma)
Multicentric (greater than 80% of canine lymphoma cases and the subject of this discussion)
Extranodal (eye, skin, etc.)
Lymphoma is a common systemic cancer (neoplasm) of the lymphatic system. Affected dogs are usually middle aged to older. The most common sign noticed early in the course of disease is enlarged lymph nodes (lymphadenopathy). The lymph node locations noticeable on physical exam include underneath the jaw, around the shoulder blades, inguinal area (end part of the abdomen where the legs meet the body), and behind the knees. These lymph nodes are both on the right and left sides. Usually all are enlarged to some degree but occasionally they are enlarged in only one area. Most people notice the ones underneath the jaw in the upper throat area (submandibular lymph nodes).
Early in the course of disease the enlarged lymph nodes may be the only sign as they seem to feel fine with normal activity and appetite. As the disease progresses, owners may notice loss of weight, condition, appetite and energy.
Diagnosis is made by either taking a biopsy or fine needle aspirate of an enlarged lymph node. A fine needle aspirate involves simply sticking a syringe into the lymph node and pulling back the plunger to get some cells in the needle. This can be done without sedation. A slide of the cells is then examined under the microscope. It is often easy to diagnose lymphoma this way as it has a characteristic appearance on the slide. Abdominal ultrasound and blood work should also be performed to determine if the lymphoma is in other parts of the body such as the liver, spleen or kidneys.
Treatment primarily consists of some combination of chemotherapy drugs. Your veterinarian may treat in the clinic or refer your pet to a veterinary oncologist. There are several protocols to choose from and most dogs will go into remission (lymph nodes return to normal size indicating a large reduction in the cancer cells). Dogs generally tolerate chemotherapy very well and actually feel better because the disease is in remission. The main side effect to be concerned about (depending on the drugs used) is a condition called leukopenia. This is where the white blood cells get low due to the bone marrow suppression caused by the chemotherapy drugs and is usually temporary and doesn’t require specific treatment. The white blood cells usually come back up to normal within a few days. However, antibiotics may be prescribed as a precaution. Some of the chemotherapy drugs commonly used to treat lymphoma are the oral medicines prednisone, cyclophosphamide and chlorambucil. Injectable drugs used in combination with the oral ones are vincristine, L-asparaginase and doxyrubicin. Remission rates vary with the protocol used but range from 4 to 11 months. While most dogs will go into remission for a time, sometimes, especially if it is a high-grade lymphoma, they will not respond very well to chemotherapy (fails to go into remission). If the lymphoma involves internal organs such as the spleen, liver or kidneys, the remission times are typically not as long (a few months compared to 6-11 months).
While lymphoma is certainly not a good diagnosis to get, it is one of the most treatable cancers where a good quality of life can maintained for a time.. Without any treatment, the pets will probably die within 1 to 2 months of diagnosis due to the cancerous lymphocytes infiltrating other organs and tissues. If financial factors prohibit normal chemotherapy protocols, single drug therapy just using prednisone (which is very inexpensive) can often result in a short term remission. It will only last 1-2 months of no other drugs are added, but it is better than no treatment at all.