Questions and Answers
What is the inherent risk of leukemic transformation in chronic myelomonocytic leukemia (CMML) over a period of 3-5 years?
In the revised WHO classification, which feature is used to categorize CMML into myeloproliferative (MP-CMML) and myelodysplastic (MD-CMML) subtypes?
What change was made regarding the diagnostic absolute monocyte count (AMC) threshold in the 2022 classification systems?
Which subcategory of CMML was removed in the 5th edition of the WHO classification due to limited risk stratification?
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What percentage of blasts is included in the categorization of CMML-1 according to the WHO classification?
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Study Notes
Overview of Chronic Myelomonocytic Leukemia (CMML)
- CMML is a clonal hematopoietic stem cell disorder with features of both myelodysplastic syndromes and myeloproliferative neoplasms.
- It is characterized by significant monocytosis and has a 15%–20% risk of leukemic transformation over 3–5 years.
Classification Changes
- CMML has been classified as a unique myeloid neoplasm since the French-American-British (FAB) classification in 1982.
- The 4th edition of the WHO classification introduced two subtypes for CMML:
- Myeloproliferative CMML (MP-CMML)
- Myelodysplastic CMML (MD-CMML)
- MP-CMML is defined by a white blood cell count of ≥13 x 10^9/L.
Recent Developments in CMML Classification
- In 2022, two classification systems for myeloid neoplasms emerged:
- International Consensus Classification (ICC)
- 5th edition of the WHO classification
- Both systems revised the diagnostic absolute monocyte count (AMC) threshold from ≥1 x 10^9/L to ≥0.5 x 10^9/L.
- Patients with sustained AMC values between 0.5 and 1.0 x 10^9/L, previously known as Oligomonocytic CMML (O-CMML), show similar outcomes and phenotypic overlaps with CMML.
Revised Subcategories
- The 5th edition of the WHO classification and ICC eliminated CMML-0 as a subcategory due to insufficient risk stratification.
- Categorization of CMML is now based on peripheral blood (PB) and bone marrow (BM) blast percentage:
- CMML-1: Includes blasts and promonocytes.
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Description
This quiz provides an overview of the latest diagnostic criteria, risk stratification, and management strategies for Chronic Myelomonocytic Leukemia (CMML) as of 2024. Designed for 3rd year hematopathology residents, it highlights essential knowledge for understanding this complex disorder and its treatment options.
