Classification of non-Hodgkin's lymphoma

Lymphomas are divided into Hodgkin’s and non-Hodgkin’s lymphomas. Since 1965 when the Rye classification [1] was proposed, there has been general agreement on the histopathology of Hodgkin’s disease such that the classification is a useful adjunct to treatment planning. However, in nonHodgkin’s lymphomas there is still confusion and controversy. As a result of the lack of fundamental understanding of lymphopoiesis and the associated incomplete cytologic characterization and identification, the classification and terminology of non-Hodgkin’s lymphomas remain in dispute. In 1 966, Rappaport [2] introduced a classification because the traditional terms lymphosarcoma and reticulum-cell sarcoma had been used in variable fashion. Rappaport’s classification emphasized cytologic features and the significance of follicle formation (nodularity). This classification has been found to be clinically relevant and reproducible histologically. Rappaport’s classification was based on two principles: cell distribution (follicular and diffuse) and cell types (lymphocytic, mixed, undifferentiated, and histocytic). Unfortunately, with the advancement of immunology and cytology some parts of Rappaport’s classification have been found to be technically and conceptually incorrect [3-5]. Nodular lymphoma has been found to arise from follicular B lymphocytes [3-5], arguments against substitution of histiocytic lymphoma for reticulum-cell