Hairy cell leukemia

ICD-O-1 Morphology
Effective 1978 - 1991
ICD-O-2 Morphology
9941/3: Leukemic reticuloendotheliosis
Effective 1992 - 2000
ICD-O-3 Morphology
9940/3: Hairy cell leukemia
Effective 2001 and later
for cases diagnosed 1978 and later
Primary Site(s)
Primary site must be bone marrow (C421)

Not Applicable
Module Rule
Alternate Names
Leukemic reticuloendotheliosis
A rare type of leukemia in which abnormal B-lymphocytes are present in the bone marrow, spleen and peripheral blood. When viewed under a microscope, these cells appear to be covered with tiny hair-like projections.

Neoplasm in bone marrow and peripheral blood composed of small B lymphoid cells with oval nuclei and abundant cytoplasm with hairy projections, diffusely infiltrating bone marrow and splenic red pulp.
Abstractor Notes
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)

The diagnosis is best made on bone marrow. HCL infiltrates are found in the red pulp of the spleen. The white pulp is typically atrophic. The liver may show infiltrates of hairy cells, predominantly in the sinusoids. Lymph node infiltration may occur especially in advanced disease.

Treatment options will depend on the following: Number of hairy cells vs healthy blood cells in the blood and bone marrow, swollen spleen, presence of infection or whether the leukemia has recurred (come back) after previous treatment. Treatment often results in long-lasting remission

Hairy Cell leukemia has the following groups:

1. Untreated Hairy Cell Leukemia: newly diagnosed

2. Progressive Hairy Cell Leukemia: previous treatment with either chemotherapy or splenectomy and the following occur: increase in number of hairy cells in the blood or bone marrow OR number of red blood cells, white blood cells or platelets is lower than normal

3. Relapsed Hairy Cell Leukemia: Leukemia has come back after treatment

4. Refractory Hairy Cell Leukemia: Nonresponsive to treatment
Definitive Diagnostic Methods
Bone marrow biopsy
Genetic testing
Genetics Data
Coexpression of multiple clonally related Ig-isotypes
VH genes with somatic hypermutation
Annexin Ai (ANXA1) expression
CD5 lacking
CD10 lacking
CD11c bright coexpression
CD20 bright coexpression
CD22 bright coexpression
CD25 expression
CD103 expression
CD123 expression
cyclin D1 weak expression
DBA.44 expression
FMC-7 expression
T-bet expression
Surgery (splenectomy)
Watchful waiting
Transformations from
Corresponding ICD-9 Codes
202.4 Leukemic reticuloendotheliosis
Corresponding ICD-10 Codes
C91.4 Hairy-cell leukemia
Corresponding ICD-10-CM Codes (U.S. only)
C91.4 Hairy-cell leukemia (effective October 01, 2015)
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
Progression and Transformation
Epidemiology and Mortality
Age: 50 years median age
Incidence: 2% of lympohid leukemias
Sex: male predominance
Survival: 10 years survival rate >90%