UNUSUAL BLAST PROLIFERATION AND KINETICS IN ACUTE LYMPHOBLASTIC LEUKAEMIA

In five cases of acute lymphoblastic leukaemia (taken from a larger series of acute lymphoblastic leukaemias) the thymidine-3H labelling index of circulating blast cells proved to be higher than that of bone marrow blasts. It was also found that the proliferating compartment was larger at peripheral level. In vivo kinetic studies of one of the five cases made it possible to quantify the sizes of bone marrow and peripheral proliferating and non-proliferating compartments. Some features of blast population kinetic behaviour differing from what is normally observed in cases of acute myeloblastic leukaemia were also brought to light. A prevalently extra-medullary origin of leukaemic cells is proposed for these special cases of acute lymphoblastic leukaemia. Thus, the circulating cells may not represent a terminal zone as in acute myeloblastic leukaemia but a transit zone with recirculation possibilities. © 1969.