ABSTRACT
The classification of lymphoid neoplasms has undergone significant change in the last several years. Previous systems were based primarily on morphologic criteria, as exemplified by the Rappaport classification, which served as the standard for almost 25 years. This approach to classification utilized both architectural features and cellular morphology to stratify cases into different categories (Table 1). Although it was both clinically useful and reproducible, it suffered from inappropriate terminology and failed to recognize specific disease entities. Large cell lymphomas of both B-cell and T-cell type
were included together in the category of diffuse histiocytic tumors. This was later recognized to be a problem, as virtually all of these neoplasms proved to be of lymphoid lineage and had no developmental relationship to tumors of histiocytes or so-called tissue-based macrophages. Therefore, the late 1960s saw the Rappaport classification fall into disfavor as it was replaced by a number of other classifications based upon new knowledge of the immune system. The two best known were the Lukes and Collins and the Kiel classifications. The former scheme was used heavily in North America, while the latter derives from Kiel, Germany and is still used frequently today in some parts of Europe. These two ‘‘competing’’ classifications incorporated new immunological data together with morphological assessment as the primary basis of classification. For the first time, lymphomas were separated into B-and T-cell types and clearly recognized in the context of normal lymphoid cell ontogeny. However, these two schemes were part of an explosion of different classification proposals that flooded the literature in the 1970s and led to mass confusion. No well-defined nomenclature existed to translate from one classification to another, rendering many clinicopathologic analyses virtually uninterruptible.
