Leukemia: stem cells, preleukemia and cure.

Several new or evolving concepts of leukemia biology and treatment are considered including: most leukèmias result from transformation of a stem cell, their phenotype reflecting the site of clonal expansion rather than transformation; most leukemias are preceded by one or more preleukemia phases; and cure may be possible by re-establishing preleukemia or forcing maturation of leukemia cells.