CD34 and acute myeloid leukemia: Concluding from our data, we would support this hypothesis: (I) normal CD34+ positive cells showed FLT3 down-regulation, (II) the down-regulation was “specific” to FLT3 and not observed in other TKR and cytokine receptor relevant in haematopoiesis and (III) AML patients with a down-regulating phenotype tend to have a better prognosis (longer survival, higher CR rates and lower peripheral blast counts).