Classification of lymphomas

Malignant lymphomas are neoplasms of cells of the lymphoreticular or immune system. Classification of these neoplasms has long been controversial and confusing. In recent years, considerable progress has been made in establishing useful and prognostically significant classifications of lymphomas. Currently, lymphomas may be divided into two main groups: Hodgkin's disease and non-Hodgkin's lymphomas. The Rye classification of Hodgkin's disease is now widely accepted and used throughout most of the world. In contrast, considerable conflict exists about the schemes of non-Hodgkin's lymphomas. The traditional classifications of non-Hodgkin's lymphomas currently used by most pathologists are based purely on morphologic grounds, and, despite the fact that they may be conceptually incorrect, they have often been shown to be useful for clinicopathologic studies. New or modern but yet untested schemes based not only on morphologic criteria, but also on recent immunologic techniques, have been proposed. This work will review the classifications of Hodgkin's disease and the non-Hodgkin's lymphomas, emphasizing the currently used schemes, describe the major modern classifications of lymphomas, and discuss and illustrate the subclasses of lymphomas and the differential diagnoses of the various types of lymphomas from nonlymphomatous proliferations which may mimic them.