Coexistence of two distinct cell populations (CD56(+)TcR gamma delta(+) and CD56(+)TcR gamma delta(-)) in a case of aggressive CD56(+) lymphoma/leukemia

Background and Objectives. Large granular lymphocytes derive from two major lineages: one expressing the CD3 surface antigen (T-lymphocytes), and the other lacking this marker (NK-cells). Although developmental overlaps betwe en natural killer cells and T-cells have been described, malignancies deriv ed from these two cell types are considered as distinct lymphoid disorders. Design and Methods. We report the case of a 30-year old man affected by a l ymphoma/leukemia syndrome presenting with hepatosplenic lymphoma which rapi dly transformed into aggressive NK-leukemia. Extensive flow cytometry studi es and molecular analysis were repeated during the course of the disease, a nd showed an unexpected changing pattern. Results. At diagnosis, flow cytometry analysis showed the co-existence of t wo cell populations, one CD56(+), CD3(+), TcR gamma delta(+), and the other CD56(+), CD3(-) and TcR gamma delta(-). Molecular analysis showed that the TcR genes had the same clonally rearranged pattern involving beta, gamma a nd delta genes in both populations. At disease relapse and during the termi nal refractory phase, only CD3(-) cells were present. Interpretation and Conclusions. This is an unusual case of CD56(+) aggressi ve lymphoma/leukemia characterized by the clonal expansion of two phenotypi cally different cell populations, variably balanced during the course of th e disease. The presence of the same TcR genomic rearrangement suggests the origin from a common progenitor able to differentiate along both T- and NK- pathways. (C) 2000, Ferrata Storti Foundation.