A B-cell malignancy that is characterized commonly by symptoms of fatigue, a markedly enlarged spleen, and a distinctive histologic appearance on peripheral blood smear and bone marrow biopsy.
The disease is not curable. However, it is highly responsive to therapy and may be managed successfully for a decade or more.
Patients who are without symptoms do not require immediate treatment; nor is early treatment beneficial in extending life expectancy.
In symptomatic patients, purine analogs have largely replaced traditional therapies, such as splenectomy, except in rare cases of splenic rupture or massive splenomegaly.
Supportive care with antibiotics, nonsteroidal anti-inflammatory drugs, administration of irradiated blood products, and granulocyte colony-stimulating factors may have a role in therapy for hairy cell leukemia.
Hairy cell leukemia (HCL) is an uncommon mature B-cell neoplasm. It was described as a distinct clinical entity in 1958.  Seen under the microscope, the cells have delicate cytoplasmic projections, resembling hair, and that is why the disease was named HCL. The disease has a characteristic presentation of pancytopenia, splenomegaly, and circulating hairy cells in blood, marrow, and other hematopoietic organs. 
USF Center for Comparative Effectiveness Research and Evidence Based Medicine
Department of Internal Medicine, College of Medicine
Moffitt Cancer Center & Research Institute, Department of Health Outcomes & Behavior
University of South Florida
AK declares that he has no competing interests.
Professor of Medicine and Oncology
Moffitt Cancer Center & Research Institute
Department of Blood and Marrow Transplantation
Department of Oncologic Sciences
University of South Florida College of Medicine
MKD declares that he has no competing interests.
Dr Ambuj Kumar and Dr Mohamed Kharfan-Dabaja would like to gratefully acknowledge Dr Benjamin Djulbegovic, a previous contributor to this monograph. BD declares that he has no competing interests.
Section of Haemato-Oncology
Brookes Lawley Institute of Cancer
DC declares that he has no competing interests.
Clinical Professor of Medicine
University of Texas Health Science Center San Antonio
RL declares that he has no competing interests.
Section of Hematology and Oncology
Department of Internal Medicine
Wake Forest University Baptist Medical Center
RC declares that she has no competing interests.
The Royal Marsden Hospital
CD declares that she has no competing interests.
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