Chronic Myelomonocytic Leukemia (CMML) 2024 Update - PDF

Chronic myelomonocytic leukemia: 2024 update on diagnosis, risk stratification and management Supervised by : DR Sadiq Khalf. By Zainab Yaseen 3rd year hematopathology resident  CMML chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder...

Chronic myelomonocytic leukemia: 2024 update on diagnosis, risk stratification and management Supervised by : DR Sadiq Khalf. By Zainab Yaseen 3rd year hematopathology resident  CMML chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder with overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms, characterized by prominent monocytosis and an inherent risk for leukemic transformation (15%–20%) over 3–5 years.  The classification of CMML as a unique myeloid neoplasm has undergone several iterations dating back to the original French-American-British (FAB) effort in 1982. Due to renewed evidence demonstrating clinical, morphological, and molecular differences, the revised 4th edition of the World Health Organization (WHO) classification of myeloid neoplasms recommended categorization of CMML into “myeloproliferative” (MP-CMML) and “myelodysplastic” (MD-CMML) subtypes; based on a white blood cell count of ≥13 x109/L for MP-CMML.  In 2022, two slightly divergent classification systems for myeloid neoplasms emerged, the International Consensus Classification (ICC) system and the 5th edition of the WHO classification system. Both systems recommended lowering the diagnostic absolute monocyte count (AMC) threshold from ≥1x109/L, to ≥0.5x109L. This was based on data demonstrating that patients with sustained AMC values between 0.5 and 1.0x109/L, with CMML-like clonal changes in HSPC, shared phenotypic overlaps and had similar outcome.  This category of patients had previously been designated as Oligomonocytic CMML (O- CMML). The 5th edition of the WHO classification and the ICC removed CMML-0 as a subcategory, due to limited risk stratification and restored categorization based on PB and BM blast % into (a) CMML-1 (blasts including promonocytes