CD34 and acute lymphoblastic leukemia: Its biological function is involved in inhibition of differentiation, expansion of hematopoietic stem cells, signaling transduction and adhesion.(45) Studies showed that in pediatric ALL, the expression of CD34 is a good prognostic factor, while in adults it is related to a worse prognosis.(46-48) CD34 expression was significantly higher in adults, and what may be associated with prognostic features of the genetic basis of the disease.