Aggressive natural killer cell leukaemia/lymphoma: report of four cases and review of the literature. Possible existence of a new clinical entity originating from the third lineage of lymphoid cells.

The morphologic, immunologic, genotypic and functional properties of peripheral blood and bone marrow cells or cultured cells from four patients with a clinically aggressive non-T, non-B natural killer cell leukaemia/lymphoma (ANKL/L) are described. The leukaemic cells possessed medium to large granules in the cytoplasm, antigens against CD38, CD2, OKIa 1 and NKH-1 CD56) monoclonal antibodies on their cell-surface, and also showed natural killer (NK) activity. In addition, these ANKL/L belonged to neither T- nor B-cell lineage, proved by studying clonal gene rearrangement for the T beta, T gamma and T delta receptors, and immunoglobulin. After comparing them with the seven cases of ANKL/L reported in other institutions, with regard to immunophenotype, genotype and function, we conclude that ANKL/L originating from a third lineage of lymphoid cells is a distinct clinical entity.