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Category: Canine
Lymphosarcoma (LSA), also called malignant lymphoma, arises from lymphocytes (a type of white blood cell) that have undergone malignant transformation. Although LSA is capable of originating in most tissues of the body, these tumors usually start in the lymph nodes, the bone marrow or the spleen. Primary lymph node LSA is the most likely explanation for your dog's lymph node enlargement, but systemic infection with bacteria, fungus or rickettsial organisms can cause lymph node swelling as well. Cancer is a cellular diagnosis; therefore, the enlarged lymph nodes should be sampled, either by fine-needle aspirate or by biopsy, to determine if lymphosarcoma is present or not.
Usually dogs diagnosed with lymph nodal LSA will have normal blood test results (i.e., there are no cancer cells seen in the blood). Leukemia (another form of white blood cell cancer) and LSA that originates in bone marrow cause cancer cells to circulate in the blood stream, so blood tests are clearly indicated. The prognosis is much poorer for patients with circulating cancer cells in the blood stream, no matter what type of cancer is present. However, the test results may not render a specific diagnosis.
Most patients with LSA will respond to treatment with prednisone, entering into a complete remission for a period of time if the doses are high enough. Unfortunately, the remission achieved with prednisone is usually lost after six to eight weeks. Commencing a full course of chemotherapy after the cancer has become resistant to prednisone lessens the likelihood that subsequently administered chemotherapeutic agents will produce a good remission.
A wide array of chemotherapy agents are effective against most lymphomas. Protocols for treatment that incorporate multiple drugs given in cycles appear to offer the longest remissions and survival times. Use of a single drug may be simpler and more economical for some patients, but does not typically produce the same quality or duration of remission. Standard chemotherapy for LSA is well tolerated by most dogs that are treated; still, it is not for every patient or every pocketbook.
Age does not necessarily impact on prognosis, but other health issues and stage of cancer will. The vast majority of patients with LSA will succumb to the disease within nine to 14 months, even with aggressive chemotherapy.
If your dog is having breathing problems he could have lung or internal lymph node involvement. These locations of cancer force more aggressive choices sometimes, including possible radiation therapy.
You may wish to speak with your doctor about referral to a veterinary specialist in internal medicine or oncology to render an opinion about your dog's diagnosis and treatment. I would certainly advise this before any presumptive treatments for cancer are attempted. Some treatments may mask the disease, making it more difficult to achieve an accurate diagnosis. |