Hairy-cell leukaemia (HCL) is an established clinicopathological entity typified by a chronic picture of substantial splenomegaly, less frequent hepatomegaly, and only inconspicuous lymphadenopathy. Central to the diagnosis is the pathognomonic hairy cell (HC), a dis- tinctive mononuclear cell that circulates in varying numbers and infiltrates a variety of organs, including the bone marrow and spleen. Peripheral pancytopenia is often present, and circulating HCs may be infrequent. HCs are invariably present in the bone marrow; but, per- haps because of the extensive fibrosis characteristic of...