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

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.