Most people diagnosed with chronic myelomonocytic leukemia (CMML) have one of three different subtypes of CMML. Doctors classify CMML subtypes by the percentage of blast cells ("blasts") in the blood and bone marrow.
Doctors use a classification system developed by the World Health Organization (WHO) in 2001 and updated in 2016. The three subtypes are:
- CMML-0, a category for cases with 2 percent blasts in the blood and 5 percent blasts in the bone marrow
- CMML-1, for cases with 2 to 4 percent blasts in the blood and/or 5 to 9 percent blasts in the bone marrow
- CMML-2, for cases with 5 to 19 percent blasts in the blood and 10 to 19 percent blasts in the bone marrow
Most healthy individuals have less than 5 percent blast cells in their developing bone marrow cells.
In addition, based on the white blood cell (WBC) count, CMML can be grouped into two subtypes:
- A dysplastic type (MD-CMML) defined by WBC < 13x109/L (liters)
- A proliferative type (MP-CMML) defined by WBC ≥ 13x109/L
- Download or order The Leukemia & Lymphoma Society's free fact sheet, Chronic Myelomonocytic Leukemia (CMML) and Juvenile Myelomonocytic Leukemia (JMML)