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Hairy cell leukaemia (HCL)

Hairy cell leukaemia (HCL) is a very rare form of cancer. It usually develops very slowly and is referred to as a chronic leukaemia.

Blood cells are formed in the bone marrow, which is the spongy tissue found inside the bones. Blood-forming stem cells divide to produce either more stem cells or immature cells that become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. Hairy cell leukaemia (HCL) is a specific type of leukaemia in which the lymphocytic (antibody producing) white blood cells that are produced by the bone marrow are affected.

A lymphoid stem cell becomes a lymphoblast cell and then one of three types of lymphocytes (white blood cells):

In HCL there is an excess number of lymphocytes in the circulating blood. These lymphocytes are abnormal and cannot help the body to defend against infections. They are called hairy cells because the cells have fine projections on the surface – which look like hairs under the microscope. When you have HCL, the marrow is not able to make enough normal blood cells.

HCL is very similar to a type of leukaemia called chronic lymphocytic leukaemia (CLL).

  • Published: Aug 2016
  • Next planned review: Aug 2018