Diagnosis, biology and treatment of hairy-cell leukaemia.

Hairy-cell leukaemia (HCL) is usually readily diagnosed by seeing typical hairy cells (HCs) in the blood film. The diagnosis is then confirmed by tartrate-resistant acid phosphatase staining, marker analysis, and bone marrow examination. HCs are clonal mature memory B cells with specific features of activation. This HC activation is responsible for many of the pathological features of the disease, including its distinctive bone marrow fibrosis, splenic red pulp invasion, and pseudo-sinus formation. Chlorodeoxyadenasine is the treatment of first choice. Deoxycoformycin and rituximab are useful for the treatment of relapsed/refractory disease. The nature of the primary oncogenic event(s) remains unknown and is the major unresolved issue in HCL.