CD9 predicts ETV6-RUNX1 in childhood B-cell precursor acute lymphoblastic leukemia

INTRODUCTION: The ETV6-RUNX1 is a fusion gene associated with a good outcome in B-cell precursor lymphoblastic leukemia. OBJECTIVE: This study aimed to re-evaluate the CD9 cellular expression by flow cytometry (FC) as a possible tool to predict the presence of ETV6-RUNX1. METHOD: Childhood B-cell precursor lymphoblastic leukemia cases were included (n = 186). The percentage of CD9-labeled cells and the median fluorescence intensity ratio were used for correlation with the molecular tests. Receiver Operating Characteristic curves were performed to determine the likelihood of the CD9 expression predicting ETV6-RUNX1. RESULTS: The ETV6-RUNX1 was found in 44/186 (23.6%) cases. Data analysis revealed that the best cutoff for CD9 percentage was 64%, with an accuracy of 0.84, whereas the best cutoff for CD9 median fluorescence intensity ratio was 12.52, with an accuracy of 0.80. A strong association was observed between the level of CD9 expression and the presence of ETV6-RUNX1. CONCLUSION: These data confirm that the CD9 expression could be used for risk stratification in clinical practice.