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Hairy Cell Leukemia

  • Amy Scholten, MPH
Publication Type:


Hairy Cell Leukemia

(HCL; Leukemic Reticuloendotheliosis)


Hairy cell leukemia (HCL) and HCL variant are slow-growing blood cancers. They affect white blood cells called B lymphocytes. White blood cells protect the body from infection. HCL cells look hairy under a microscope. Illness happens when these cells build up in the bone marrow and spleen.

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Leukemia starts in the bone marrow where blood cells are made. It happens when certain blood cells divide without control or order. The abnormal cells crowd out the healthy blood cells. This causes many of the symptoms.

The cause of HCL is not clear. It may be linked to changes in a gene.

Risk Factors

HCL is more common in men and people over 50 years old.


There may be no symptoms at first. Symptoms of HCL usually develop slowly over time.

They may include:

  • Belly swelling
  • Fever
  • Night sweats
  • Easy bruising
  • Painless lumps in the neck, underarms, stomach, or groin


The doctor will ask about your symptoms and health history. A physical exam will be done.

Tests may be done, such as:

  • Blood tests—to look at blood cell counts
  • Bone marrow biopsy—a sample of bone marrow is taken and tested

Images may be taken of bodily structures with a CT scan.


The treatment of HCL depends on symptoms. Treatment may not be needed at first. As HCL progresses, treatment may include:

  • Splenectomy—surgery to remove an enlarged spleen
  • Blood transfusion—to replace low numbers of blood cells
  • Chemotherapy drugs by mouth, injection, or IV— to kill cancer cells
  • Targeted medicines to help the body fight the hairy cells
  • Antibiotics or other medicines to fight or prevent infection


There are no current guidelines to prevent HCL.





  • General information about hairy cell leukemia treatment. National Cancer Institute website. Available at: Accessed March 25, 2021.
  • Hairy cell leukemia. EBSCO DynaMed website. Available at: Accessed March 25, 2021.
  • Hairy cell leukemia. Leukemia & Lymphoma Society website. Available at: Accessed March 25, 2021.
  • Sarvaria A, Topp Z, et al. Current therapy and new directions in the treatment of hairy cell leukemia: a review. JAMA Oncol. 2016;2(1):123-9.
  • Treating hairy cell leukemia. American Cancer Society website. Available at: Accessed March 25, 2021.
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.