Overview of Chronic Myelomonocytic Leukemia

Questions and Answers

A clonal hematopoietic stem cell disorder with overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms.

20%–25%

10%–15%

5%–10%

15%–20% (correct)

False

Myeloproliferative CMML (MP-CMML) and myelodysplastic CMML (MD-CMML). Signup and view all the answers

≥13 x 10^9/L Signup and view all the answers

0.5 x 10^9/L Signup and view all the answers

Study Notes

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.

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.

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.

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.