Classification of malignant lymphoma

Over the past 30 years different lymphoma classifications were used world-wide. In Europe, the Kiel classification of K. Lennert dominated the scene, it was updated 1988 and 1992. In North America the Working Formulation, primarily designed to be an instrument for translation of one classification into the other, was predominantly used. Both classifications, however, showed little correspondence with each other, which made it difficult to compare the results of randomized clinical trials on both sides of the Atlantic Ocean. In 1994 the Revised European American Lymphoma (R.E.A.L.) classification was proposed by the International Lymphomas Study Group (ILSG). In contrast to the existing classifications it abandoned the grading of malignancies. The ILSG focused on diagnostic reproducibility and on the definition of distinct clinical-pathological lymphoma entities. Similar to the Kiel classification the new classification scheme was based on cell lineage (T- and B-cell origin) and cell differentiation (precursor and mature lymphomas) and included a number of distinct extranodal lymphomas. The new WHO classification is basically identical with the R.E.A.L. scheme and exhibits only minor changes. The WHO classification includes all hematopoietic and lymphoid neoplasms. It represents the first generally accepted classification, providing hematologists and oncologists with a solid diagnostic basis for therapeutic decisions.