CD34 expression is associated with poor clinical outcome in patients with acute promyelocytic leukemia.

This study investigated the clinical characteristics and prognostic relevance of CD34 expression in 47 patients with acute promyelocytic leukemia (APL), showing t(15;17) or PML/RARalpha. Ten (21.3%) of the APL patients were CD34(+). CD34 expression was associated with hypogranular morphology (P = 0.002) and hyperleukocytosis (P = 0.015). However, there were no statistically significant differences in age, sex, hemoglobin level, platelet count, or percentage of blasts between the CD34(+) and CD34(-) APL groups. Multiplex RT-PCR analysis showed that the L-form (BCR1) and S-form (BCR3) were correlated with CD34(-) APL and CD34(+) APL, respectively. Despite the lack of a difference in the complete remission rate, overall survival (OS) and disease-free survival (DFS) were significantly lower in the CD34(+) group than in the CD34(-) group (P = 0.012 and P = 0.0051, respectively). By multivariate analysis, the CD34(+) group showed a significant independent variable in DFS compared with the CD34(-) group, but this was not demonstrated for OS. In conclusion, CD34 expression in APL is a unique clinical feature associated with leukocytosis and atypical morphology with hypogranular pattern and is associated with a poor clinical outcome.