Canine Lymphosarcoma : Diagnosis and Treatment

This article discusses the diagnostic and treatment approach to canine lymphosarcoma (LSA). Several conclusions can be drawn from the extensive body of studies on canine LSA in clinical and pathologic medicine: It is now recognized that this disease has great clinical and histologic heterogeneity; in most cases, survival can be improved with combination chemotherapy; and drug resistance is a major impediment to treating the relapsed disease. Different chemotherapy regimens are discussed along with their survival rates. Newer drugs undergoing clinical trials and the mechanism of drug resistance eventually leading to therapy failure are also discussed. Most clients are very satisfied with chemotherapy for their pets because it provides prolonged, good-quality survival and the side effects are reasonably mild. The treatment approach to canine lymphosarcoma (LSA) and nonHodgkin’s lymphoma (NHL) in humans is changing rapidly as new discoveries in the areas of chemotherapy, immunotherapy, and molecular therapeutics hold significant promise for improvement in duration of overall survival and remission rates. An area of active investigation is detection of molecular targets for therapy. In addition, the technique of immunophenotyping to distinguish between T cell and B cell subtypes of LSA is now more readily available to the practicing veterinarian. Although there is a certain uniformity in clinical presentation among dogs with LSA, the biologic behavior, histologic subtype, immunophenotype, therapeutic response, and outcome show a great deal of heterogeneity. Treating canine LSA is generally quite rewarding to the practicing clinician, and owners increasingly seek advanced treatments for their companion animals. Most clients are very satisfied with results of chemotherapy because side effects are mild and the treatment provides prolonged, good-quality survival. DIAGNOSIS AND CLINICAL STAGING Diagnosis of LSA is not a major challenge for dogs that present with generalized peripheral lymphadenopathy. Confirmatory diagnosis can easily be established by aspiration cytology (Figure 1) of an enlarged lymph node or cutaneous n In most cases, lymphosarcoma is clinically characterized by diffuse body system