Chronic myelomonocytic leukemia

ICD-O-1 Morphology

9863/3: Chronic myeloid leukemia, NOS
Effective 1978 - 1991

ICD-O-2 Morphology

9868/3: Chronic myelomonocytic leukemia
Effective 1992 - 2000

ICD-O-3 Morphology

9945/3: Chronic myelomonocytic leukemia
Effective 2001 and later


for cases diagnosed 1978 and later

Primary Site(s)

Primary site must be bone marrow (C421)

Abstractor Notes

The peripheral blood and bone marrow are always involved. The spleen, liver, skin and lymph nodes are the most common sites of extramedullary infiltration. The peripheral blood has persistent monocytosis. There are fewer than 20% blasts in the peripheral blood and bone marrow.

The physician will run tests to exclude the BCR-ABL1 fusion gene, the rearrangement of PDGFRA or PDGFRB. The physician uses the information from these tests to do a diagnosis of exclusion (clinical diagnosis) of Chronic myelomonocytic leukemia.

For more information, see the NCI website:

Diagnostic Confirmation

This histology can be determined by positive histology (including peripheral blood) with or without genetics and/or immunophenotyping. Review the Definitive Diagnostic Methods, Immunophenotyping and Genetics Data sections below, and the instructions in the Hematopoietic Manual for further guidance on assigning Diagnostic confirmation.


Not Applicable

Module Rule


Alternate Names

Chronic myelomonocytic leukemia-0
Chronic myelomonocytic leukemia-1
Chronic myelomonocytic leukemia-2
Chronic myelomonocytic leukemia in transformation [OBS]
Chronic myelomonocytic leukemia, NOS
Chronic myelomonocytic leukemia, Type I
Chronic myelomonocytic leukemia, Type II
Chronic myelomonocytic syndrome
CMML with eosinophilia
Subacute myelomonocytic leukemia


CMML is a clonal disorder of a bone marrow stem cell, in which monocytosis is a major defining feature. The clinical, hematologic and morphologic features of CMML are heterogeneous, and vary along a spectrum from predominantly myelodysplastic to mainly myeloproliferative in nature.

A slowly progressing type of myelodysplastic/myeloproliferative disease in which too many myelomonocytes (a type of white blood cell) are in the bone marrow, crowding out other normal blood cells, such as white blood cells, red blood cells and platelets. Also called chronic myelomonocytic leukemia.

Definitive Diagnostic Methods

Bone marrow biopsy
Clinical diagnosis
Genetic testing
Peripheral blood smear

Genetics Data

Structural abnormalities of 12p


CD13+ (expression/positive)
CD33+ (expression/positive)


Hematologic Transplant and/or Endocrine Procedures

Transformations from


Corresponding ICD-9 Codes

206.1 Chronic monocytic leukemia

Corresponding ICD-10 Codes

C93.1 Chronic monocytic leukemia

Corresponding ICD-10-CM Codes (U.S. only)

C93.1 Chronic myelomonocytic leukemia (effective October 01, 2015)

Signs and Symptoms

Increased white blood count (WBC) (in some cases)
Night sweats
Weight loss

Diagnostic Exams

Blood chemistry studies
Cytogenetic analysis
Peripheral blood smear

Progression and Transformation

Transformation to AML occurs in ~15-30% of cases

Epidemiology and Mortality

Age: 65-75 years median age
Incidence: 12.8 cases per 100,000 persons per year
Sex: male predominance
Survival: 20-40 months median survival


Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds):
WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition)
IARC: Lyon 2017
Section: Myelodysplastic/myeloproliferative neoplasms
Pages: 82-86

International Classification of Diseases for Oncology, Third Edition, Second Revision. Geneva: World Health Organization, 2020.
Section: ICD-O-3.2 (2020) Morphological Codes

National Cancer Institute
Section: General Information About Myelodysplastic/ Myeloproliferative Neoplasms (MDS/MPN)