Clonal Remissions in Acute Nonlymphocytic Leukemia: Evidence for a Multistep Pathogenesis of the Malignancy

Abstract TWO TYPES of clinical remission have been identified in acute nonlymphocytic leukemia (ANL). In one form, remission is characterized by repopulation of the marrow by normal stem cells; in the other type, the abnormal clone found at diagnosis persists throughout remission. 1 , 2 , 3 , 4 , 5 Among the explanations for the latter occurrences (“clonal remissions”), the hypothesis we favor is that in some patients ANL has a multistep pathogenesis with a preleukemic phase. Induction chemotherapy ablates overtly leukemic cells, thereby inducing a clinical remission. However, the marrow is not entirely repopulated by normal progenitors but by varying numbers of clonal, “preleukemic” stem cells.