Navigating diagnostic shifts: A comparative review of the WHO 5th edition and ICC 2022 classifications of myeloid neoplasms.

The near-simultaneous publication of the World Health Organization (WHO) 5th Edition classification of hematolymphoid tumors (WHO-HAEM5) and the International Consensus Classification (ICC) in 2022 represents a pivotal moment in the taxonomy of myeloid neoplasms. Both systems emphasize integration of morphology, cytogenetics, and molecular genetics, yet they diverge in several clinically meaningful areas, including blast thresholds for acute myeloid leukemia (AML), definition of the myelodysplastic syndrome (MDS)-AML interface, and categorization of TP53-mutated disease [TP53mut MN] [1-3]. These differences extend beyond nomenclature, influencing prognostic stratification, therapeutic decision-making, and eligibility for clinical trials [4-7]. Recent comparative cohort studies demonstrate substantial reclassification rates, particularly among MDS with excess blasts, AML with myelodysplasia-related features, and TP53-mutated neoplasms, with prognosis driven largely by underlying molecular features rather than blast percentage alone [8-11]. This review provides a comprehensive comparison of WHO-HAEM5 and ICC 2022, synthesizes emerging real-world outcome data, and discusses implications for diagnostic practice, harmonization efforts, and future refinement of myeloid neoplasm classification [12-14].