| [ Summary ] |
The new World Health Organization classification of tumors of the hematopoietic and lymphoid tissues recognizes three major categories of lymphoid neoplasms : B cell neoplasms, T and NK cell neoplasms, and Hodgkin's lymphomas. Within the B and T/NK cell categories, two major categories are recognized as precursor and peripheral or mature neoplasms, corresponding to the stages of differentiation of postulated normal counterparts in the immune system. There are a large numher of distinct diseases in each category, especially with peripheral or mature neoplasms. Each disease is classified according to its morphologic features as well as its immunophenotype. Furthermore, there are differences from previous classifications of lymphomas, in the estahlishment of several new entities according to epidemiology, aetiology, clinical features and responses to therapy. Since new immunophenotypic and genetic information has heen gathered, revision is necessary to update the classification. This classification is a critical test for an ideal international classification of malignant lymphomas, although it has a large numher of problems that will need to be resolved in the future. |