APIH243885243 - CME/CMLE - New Classification System of Hematologic Malignancies-APIH243885243

APIH243885243 - Educational Activity

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This educational commentary by Andrea M. Torres discusses the new International Consensus Classification (ICC) system for hematologic malignancies, introduced in 2021, as an expansion and refinement of the longstanding World Health Organization (WHO) classification system. The ICC was developed in response to changes in the WHO's revision process, which moved away from the traditionally rigorous Clinical Advisory Committee (CAC) review, prompting experts to establish the ICC to maintain a thorough, collaborative review approach. Both systems aim to classify hematologic neoplasms using morphology, genetics, immunophenotyping, and clinical features, but the ICC incorporates recent advances in genetic sequencing to improve diagnostic precision and treatment prediction.<br /><br />Key differences between the ICC and WHO include changes in terminology and diagnostic criteria across various myeloid and lymphoid neoplasms. For example, in myelodysplastic syndromes (MDS), the ICC merges the WHO's two excess blast categories into one (MDS-EB) and reclassifies higher-risk cases as MDS/AML. In acute promyelocytic leukemia (APL), both systems agree on the presence of the PML:RARA gene fusion but differ slightly in blast count definitions. For chronic myelomonocytic leukemia (CMML), the ICC lowers the threshold for monocytosis from 1.0 to 0.5 x10^9/L and requires genetic clonal markers for diagnosis, emphasizing mutation analysis for prognosis.<br /><br />In lymphoid neoplasms, the ICC prefers the term "multiple myeloma" over "plasma cell myelomas" used by WHO, and uniquely recognizes B prolymphocytic leukemia (B PLL) as a distinct disease, unlike the WHO which considers it related to transformations from other B-cell lymphomas. The ICC also allows diagnosis of lymphoplasmacytic lymphoma (LPL) with smaller marrow aggregates, emphasizing genetic testing for MYD88 and CXCR4 mutations.<br /><br />In conclusion, both WHO and ICC classifications are respected and used globally. The ICC complements and enhances WHO criteria by integrating modern genetic insights, providing clinicians and pathologists with a more nuanced framework for diagnosis and treatment of hematologic cancers.

Keywords

International Consensus Classification

ICC

World Health Organization

WHO

hematologic malignancies

myelodysplastic syndromes

acute promyelocytic leukemia

chronic myelomonocytic leukemia

lymphoid neoplasms

genetic sequencing