Histological Study of Bone Marrow Regeneration following Chemotherapy for Acute Myeloid Leukaemia and Chronic Granulocytic Leukaemia in Blast Transformation

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Abstract
Summary Haemopoietic regeneration following chemotherapy was studied on serial bone‐marrow trephine specimens from 10 patients with acute myeloid leukaemia (AML), and seven with chronic granulocytic leukaemia (CGL) in blast transformation. In AML following the stage of treatment‐induced hypoplasia during which the marrow was extremely hypocellular, oedematous, and contained widely dilated sinuses, areas of large, uniform, unilocular fat cells, designated ‘structured fat’ developed from multilocular precursor fat cells. Early foci of haemopoietic regeneration were present almost exclusively in areas of structured fat: only scattered small erythropoietic foci were seen in the earliest specimens taken 1 week after the completion of treatment; small granulopoietic foci were first seen 2 weeks later, and the first megakaryocytes were not seen until the third week. Transient regeneration was observed in two patients who subsequently failed to enter remission and died.The pattern of haemopoietic regeneration in CGL in blast transformation treated by intensive therapy and autografting with cryopreserved buffy‐coat cells differed from that seen in AML. Bone marrow regeneration occurred earlier than in AML and appeared to be independent of the presence of structured fat. Regeneration in all three cell lines appeared simultaneously within 2 weeks of autografting. Regeneration tended to be focal, each aggregate consisting almost exclusively of erythroid, granulocytic or megakaryocytic cells.The proximity of regenerating haemopoietic foci to structured fat in AML suggests that, in some circumstances, haemopoietic stem cells require the presence of fat cells in their immediate environment before they proliferate.