Chronic Myelomonocytic Leukemia (CMML) Subtypes, Stages, and Risk Groups

Subtypes of chronic myelomonocytic leukemia (CMML)

CMML has 2 main subtypes, based on a person's white blood cell (WBC) count when they are diagnosed: 

• Proliferative (CMML-MPN): the WBC count is at least 13,000 per microliter
• Dysplastic (CMML-MDS): the WBC count is less than 13,000 per microliter

In general, people with the dysplastic subtype tend to do better than people with the proliferative subtype.

Stages of chronic myelomonocytic leukemia (CMML)

Most types of cancer can be described in stages, based on how far the cancer has spread in the body. But CMML is a disease of the bone marrow and blood, so it has already spread throughout the body when it's first found. Instead, CMML is split into 2 stages based on the percentage of blasts (very immature cells) in the blood and bone marrow:

• CMML-1: Blasts make up less than 5% of white cells in the blood and less than 10% of the cells in the bone marrow.
• CMML-2: Blasts make up 5% to 19% of the white cells in the blood, or they make up 10% to 19% of the cells in the bone marrow.

Risk groups for chronic myelomonocytic leukemia (CMML)

When determining the outlook and treatment options for people with CMML, different factors are used to put people into risk groups. Several different systems can be used to classify CMML in this way. Some of the factors that these systems consider include:

• A person's age
• Their WBC count
• The percentage of WBCs that are blasts
• Their hemoglobin level (a protein in red blood cells), and how often they need red blood cell transfusions
• Their blood platelet count
• If the leukemia cells have certain gene changes

In general, CMML is divided into lower-risk and higher-risk groups, although different systems rely more on certain factors to determine this than others do.

Other factors can also be important in determining a person's treatment options, including if the CMML is causing symptoms and a person's overall health and personal preferences.