The multiface morphology of acute leukemia.

Three distinct morphological phases during the course of acute leukemia in a 16 year old girl are described. The patient presented with morphology of acute lymphoblastic leukemia, relapsed with acute myeloblastic leukemia which later on evolved to monoblastic phase. This clinical, morphological and ultrastructural observation provides clinical evidence supporting the current concept of normal and leukemic haematopoiesis, as well as clonal evolution, according to which a stem cell is capable of giving rise to different haematopoietic lineages. It is conceivable that chemotherapy altered the balance between the stem cells and the bone marrow microenvironmental stromal cells, resulting in clonal evolution or release of a new subclone with the disease relapse.