Comparison of the World Health Organisation and International Consensus Classification of haematolymphoid tumours

Background: The World Health Organization has updated its classification of haematolymphoid tumours to the new 5th edition. The International Consensus Classification is another group that has developed a separate classification system with similar but conflicting approaches. This led to a debate among haematologists about which classification system is more appropriate for clinical use. This article examines and compares these contrasting and concurring classifications, and provides insight into the utility of each system. Methods: Journal articles pertaining to WHO-HAEM4R, WHO-HAEM5 and ICC were searched for using the MEDLINE database, from November 2022 to November 2023. Original research articles and reviews were selected to compile this review. Results: The classification systems share many similarities with minor name changes and subgrouping. There are few instances where diagnostic grouping differs between the classifications, which could have clinical implications regarding treatment and enrolment in clinical trials. Conclusion: There is universal agreement about the need for objective criteria for the classification of haematolymphoid tumours. As a result, there have been considerable strides in the classification with regard to morphologic, immunophenotypic, molecular and cytogenetic characterisation. It is reassuring to have a stepwise approach to diagnosis, allowing developing countries to make appropriate diagnoses. Contribution: Harmonisation is needed for a universal diagnostic system for the benefit of the patient. Both classification systems have merit and either could be adopted by individual institutions at present. The authors appeal for interim advocacy measures to assure access to the specific diagnostic investigations in poorly resourced societies, pending more permanent and sustainable access.