|MadSci Network: Medicine|
Dear Michelle, The lymphomas are malignancies that arise from lymphocytes in various stages of differentiation or development. In general, the classification of lymphomas are based on the developmental stage of lymphocyte that gives rise (or is believed to give rise) to the malignant clone of cells. The classification of lymphomas has been somewhat controversial over the years, but the classification systems have themselves evolved recently as more has been learned about the molecular biology of lymphomas. The earlier classifications, such as the Rapaport (1966) and Kiel (1978) systems, relied largely on morphologic features (appearance under the microscope) and immunologic features (surface markers) of the malignant lymphocytes. The Working Formulation, published in 1981, was a simplified system that relied on morphologic criteria only and was found to be reproducible and a fairly good predictor of prognosis. The Revised European-American Lymphoma (REAL) classification, published in 1994, is the most up-to-date and comprehensive system, taking into account morphologic, immunologic and cytogenetic (chromosomal abnormalities) features. An update of the REAL classification by the World Health Organization (WHO) is currently under development. In addition to exhibiting different laboratory features as described above, different types of lymphoma have different clinical features which are often very predictable based on the classification of the lymphoma. Some types of lymphoma (often referred to as indolent or low-grade lymphomas) are characterized by a very slowly progressive course over many years, with patients often feeling well and not requiring any treatment for some time before symptoms develop. While these lymphomas often respond well to drug treatment (chemotherapy) and radiation therapy, they nearly always relapse eventually and thus are usually not curable. In contrast, aggressive or intermediate- or high-grade lymphomas typically grow more rapidly and produce symptoms in most patients (rather than being present without symptoms). While these lymphomas behave more aggressively, cure may be possible with aggressive chemotherapy and/or radiation therapy. Other special categories of lymphoma have distinctive features (such as mycosis fungoides which typically affects the skin). Recent developments in the treatment of lymphomas have included the use of monoclonal antibodies such as rituximab, which targets the CD20 surface marker on lymphoma cells. These agents have improved the success rate of present treatments while adding very little in the way of adverse effects. Good luck! - Steve Lattanzi, M.D. (firstname.lastname@example.org) References DeVita VT, Hellman S, Rosenberg SA. Cancer: principles and practice of oncology. Ed. 6. Philadelphia, PA: Lippincott, Williams & Wilkins, 2001. 2215-35. Banks PM. Histopathology of malignant lymphomas. In: Williams WJ, Beutler E, Erslev AJ, Lichtman MA. Hematology. Ed. 4. New York, NY: McGraw-Hill, 1990. 1031-8.
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