The 5th edition of the WHO classification of lymphoid neoplasms-an overview

The "Blue Book" of the WHO classification of haematolymphoid tumours is the worldwide accepted reference in malignant tumours of the myeloid and lymphoid system. The REAL classification of 1994 [2] laid the foundations for the WHO volumes, with continous development and specification to date [3, 5, 6]. In the 5th edition of the classification to be released this year, new insights concerning the pathogenesis and molecular genetics, and new concepts regarding the taxonomic basis of the classification are included. Overviews of the changes and new aspects of the 5th edition of the classification of haematolymphoid tumours (WHO-HAEM5) have recently been published [1,4]. Overall, 420 authors participated on the WHO-HAEM5, among them numerous members of the large international societies for haematopathology, the European Association for Haematopathology (EAHP) and the Society for Hematopathology(SH).The WHO-HAEM5 was developed in a multidisciplinary setting in numerous online meetings with haematopathologists, haematologists, oncologists, geneticists, epidemiologists and molecular biologists. In extensive discussions, harmonisation of chapters and with the other volumes of the 5th series was sought. For implementation of clinical aspects, a clinical advisory board was consulted. The new classification constitutes a systematic update of former classifications. As has been implemented earlier, the entities are presented in a hierarchical order: category (e.g. mature B-cell neoplasm), family/class (e.g. diffuse large B-cell lymphoma, DLBCL), entity (e.g. DLBCL, not otherwise specified, NOS) and subtype (e.g. DLBCL, NOS, GCB-type). Similar to the 5th editions of other WHO classifications, at the end of each chapter, a list of "essential" diagnostic criteria representing minimal criteria to establish the diagnosis and "desirable" diagnostic criteria are given in order to further confirm and specify the diagnosis.