Search Database ICD-O-3 Code Lists

Name

Hairy cell leukemia (HCL)

ICD-O-3 Morphology

9940/3: Hairy cell leukemia
Effective 2001 and later

Reportable

for cases diagnosed 1978 and later

Primary Site(s)

C421
Primary site must be bone marrow (C421)

Coding Manual: Hematopoietic Coding Manual (PDF)

Abstractor Notes

Hairy cell leukemia (HCL) is part of the Mature B-cell neoplasms lineage table in the WHO 5th edition of Hematolymphoid Tumors. (See Appendix B in the Hematopoietic Manual, Table B15)

Do NOT use this code for hairy cell leukemia variant (See 9591/3). When HCL is diagnosed in people in their 20's, it is hairy cell leukemia variant (9591/3)

HCL involves the bone marrow, spleen, and peripheral blood. Significant lymphocytosis is infrequent. Lymphadenopathy and infiltration of extranodal sites, such as the liver, bone, skin, breast, and brain, occur rare.

Watchful waiting, or observation, is a common treatment modality for patients who are asymptomatic.

In the past, Splenectomies were done to normalize the peripheral blood. The frequency of this procedure is decreasing since it does not appear to prevent progressive disease or improve long term survival.

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.

Module Rule

None

Alternate Names

Leukemic reticuloendotheliosis

Definition

Hairy cell leukemia (HCL) is an indolent mature B-cell neoplasm composed of neoplastic cells with abundant cytoplasm and characteristic hairy projections that usually involve the bone marrow, peripheral blood, and spleen and bear the BRAF p.V600E somatic mutation in ≥ 95% of cases. (WHO 5th edition)

Definitive Diagnostic Methods

Cytogenetics
Genetic testing
Histologic confirmation
Immunohistochemistry
Immunophenotyping

Genetics Data

BRAF V600E mutations

Immunophenotyping

Annexin Ai (ANXA1)+ (expression/positive)
CD5- (no expression/lacking/negative)
CD10- (no expression/lacking/negative)
CD11c+ (expression/positive)
CD20+ (expression/positive)
CD22+ (expression/positive)
CD25+ (expression/positive)
CD103+ (expression/positive)
CD123+ (expression/positive)
CD200+ (expression/positive)
Cyclin D1+ (expression/positive)
DBA.44+ (expression/positive)
FMC7+ (expression/positive)
TBX21 (TBET)+ (expression/positive)

Treatments

Chemotherapy
Immunotherapy
Surgery

Transformations to

Transformations from

None

Same Primaries

Corresponding ICD-10 Codes (Cause of Death codes only)

C91.4 Hairy-cell leukemia

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

C91.4 Hairy-cell leukemia (effective October 01, 2015 - September 30, 2024)
C91.4 Hairy-cell leukemia not having achieved remission (effective October 01, 2024)
C91.4 Hairy-cell leukemia, in remission (effective October 01, 2024)
C91.4 Hairy-cell leukemia, in relapse (effective October 01, 2024)

Signs and Symptoms

Easy bruising or bleeding
Fever or frequent infections
Pain or a feeling of fullness below the ribs
Painless lumps in the neck, underarm, stomach or groin
Shortness of breath
Weakness or feeling tired
Weight loss for no known reason

Diagnostic Exams

Blood chemistry studies
Bone marrow aspiration and biopsy
CT (CAT) scan
Cytogenetic analysis
Flow cytometry
Immunophenotyping
Peripheral blood smear

Progression and Transformation

None

Epidemiology and Mortality

Age: 50 years median age
Incidence: 2% of lympohid leukemias
Sex: male predominance
Survival: 10 years survival rate >90%

Sources

WHO Classification of Tumours Editorial Board. Haematolymphoid tumours. Lyon (France): International Agency for Research on Cancer; 2024. (WHO classification of tumours series, 5th ed.; vol. 11). https://publications.iarc.who.int/637.
Section: Splenic B-cell lymphomas and leukemias
Pages: Part B: 380-384

International Classification of Diseases for Oncology, 3rd edition (including revisions). Geneva: World Health Organization, 2001, 2011, 2020.
Section: ICD-O-3.2 (2020) Morphological Codes
Pages: http://www.iacr.com.fr/index.php?option=com_content&view=category&layout=blog&id=100&Itemid=577

PDQ® Adult Treatment Editorial Board. PDQ Hairy Cell Leukemia Treatment. Bethesda, MD: National Cancer Institute. Updated <02/21/2025>. Available at: https://www.cancer.gov/types/leukemia/hp/hairy-cell-treatment-pdq. Accessed <03/04/2025>. [PMID: 26389184]
Section: Hairy Cell Leukemia Treatment (PDQ®)–Health Professional Version
Pages: https://www.cancer.gov/types/leukemia/hp/hairy-cell-treatment-pdq
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