WHO classification of tumours of haemopoietic and lymphoid tissues - what's new in the lymphomas?

Abstract

The World Health Organization (WHO) Classification of Tumours of the Haemopoietic and Lymphoid Tissues (4th Edition), published in 2008, incorporates new information that has emerged from basic and clinical investigation in the interval since publication of the 3rd edition. Most of the changes are incremental but some have implications for clinical management. A number of EBV-related diseases of both T-cell and B-cell lineage have been defined and included. Cutaneous lymphomas of B-cell and T-cell lineage recently defined in the consensus EORTC/WHO classification have been incorporated into what is now a single classification scheme and these account for many of the changes in the T/NK cell neoplasms. ‘Blastoid T/NK cell lymphoma’, now understood to be a tumour of plasmacytoid dendritic cell origin, is reclassified under acute myeloid leukaemia and related precursor neoplasms. In the indolent B-cell lymphomas, paediatric variants of follicular and marginal zone lymphomas have been added. In the aggressive B-cell neoplasms, diffuse large b-cell lymphoma, its many variants and its interface with Burkitt lymphoma and classical Hodgkin lymphoma has been revised and developed with the inclusion of borderline categories which have implications for both diagnosis and management. The World Health Organization (WHO) Classification of Tumours of the Haemopoietic and Lymphoid Tissues (4th Edition), published in 2008, incorporates new information that has emerged from basic and clinical investigation in the interval since publication of the 3rd edition. Most of the changes are incremental but some have implications for clinical management. A number of EBV-related diseases of both T-cell and B-cell lineage have been defined and included. Cutaneous lymphomas of B-cell and T-cell lineage recently defined in the consensus EORTC/WHO classification have been incorporated into what is now a single classification scheme and these account for many of the changes in the T/NK cell neoplasms. ‘Blastoid T/NK cell lymphoma’, now understood to be a tumour of plasmacytoid dendritic cell origin, is reclassified under acute myeloid leukaemia and related precursor neoplasms. In the indolent B-cell lymphomas, paediatric variants of follicular and marginal zone lymphomas have been added. In the aggressive B-cell neoplasms, diffuse large b-cell lymphoma, its many variants and its interface with Burkitt lymphoma and classical Hodgkin lymphoma has been revised and developed with the inclusion of borderline categories which have implications for both diagnosis and management.