Hairy cell leukemia

Synonyms: HCL

Medical Specialties: Internal medicine, Oncology

Clinical Definition

Hairy cell leukemia (HCL) is a cancer of the bone and blood marrow characterized by the bone marrow overproducing lymphocytes. The rare cancer either progresses slowly or not at all, with fever, weakness and fever among the symptoms. Treatments may include chemotherapy, surgery, stem cell transplants or biologic therapy to boost the immune system.

In Our Own Words

Hairy cell leukemia (HCL), a cancer of the blood and bone marrow, is named after the hairy appearance of leukemia cells when viewed under a microscope. Normally, bone marrow makes blood stem cells, defined as immature cells that develop over time into mature blood cells. However, in HCL, too many of these stem cells develop into white blood cells known as lymphocytes. Lymphocytes are abnormal cells (i.e., not healthy white blood cells), and they can build up and crowd out the healthy white blood cells, red blood cells and platelets.


This cancer is rare and tends to be slow growing. Some patients only need to be monitored closely if the cancer is not progressing. For others, treatment options include chemotherapy, stem cell transplants, surgery or therapy to boost the immune system.

Relevant Conditions
  • Cytopenias
  • Enlarged spleen
Side Effects
  • Abdominal fullness due to enlarged spleen
  • Fatigue
  • Weakness
  • Frequent infections
  • Fever
  • Easy bruising or bleeding
Share this article
  • The Cleveland Clinic. "Hairy Cell Leukemia." Accessed August 2013.
  • American Cancer Society. "Treating hairy cell leukemia." Updated July 2013. Accessed August. 2013.
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