Adult and childhood acute lymphoblastic leukemia: clinico-biological differences based on CD34 antigen expression.

Background and Objective: The prognostic significance of CD34 antigen expression in acute lymphoblastic leukemias (ALL), especially in adult patients, is still not well established. In the present report we analyzed a series of biological and clinical findings from 128 ALL patients in order to evaluate the possible clinical significance of this marker.
Methods: The clinical and biological significance of CD34 expression, an early marker of hemopoietic cells, was analyzed by flow cytometry in a series of 128 patients affected by ALL, including 78 adults and 50 children under 15 years old.
Results: Overall, 68.7% of patients showed significant ( > 10%) CD34 expression. There was no difference between CD34+ and CD34- ALL with respect to age, sex, FAB morphology, hepatosplenomegaly, Plt count, Hb level, DNA index, P-170 expression. CD34+ ALL displayed a significantly lower frequency of extramedullary involvement, a lower LDH level and lower WBC count, lower proliferative activity (as evaluated by the Ki67 monoclonal antibody) than CD34- ALL. CD34 expression was also associated with early phenotypes in both B- and T-ALL, co-expression of myeloid antigens, and the presence of the Ph1 chromosome. Due to a different distribution of prognostic factors investigated, DFS and OS were both significantly better in CD34+ than in CD34- childhood ALL, whereas no statistical difference was found in adults. Multivariate analyses confirmed these data in children.
Interpretation and Conclusions: Expression of the CD34 antigen is a positive prognostic factor in childhood ALL. In adult ALL the presence of this marker on leukemic cell does not seem to influence the clinical outcome of these patients.