Fluctuations in the T and B characteristics of two cases of T-cell hairy-cell leukaemia.

A new case of hairy-cell leukaemia (HCL) in which the hairy cells (HCs) formed spontaneous sheep erythrocyte (E) rosettes is described, and this E-rosette formation is shown to be an active process independent of surface immunoglobulin (SIg). Sequential studies with a panel of markers of this and of a case of HCL with T-cell features previously described from this laboratory show that both these cases, at certain times of study, possessed combined T- and B-cell features. Extensive follow-up study revealed wide fluctuations in the surface phenotype of peripheral blood (PB) mononuclear cells, while the total leucocyte count remained stable. At various times, the PB mononuclear cells showed the following phenotypes: E+SIg+gamma Fc+C3-, E-SIg-gamma Fc+C3-, E+SIg-gamma Fc+/-C3-, and the significance of these phenotypic changes is discussed. The importance of sequential studies with a panel of markers in the characterization of lymphoproliferative disorders is emphasized.