In summary, our patient samples and the database expression data correlated in regard to Plk1 and Plk4, as the expression was higher in B-ALL patients than in both PBMCs and in CD19+ sorted B-cells from healthy donors but differed in regard to Plk2 and Plk3 as an opposite expression pattern was found in our patients compared to the database set. This evidence concerns the gene PLK1 and precursor B-cell acute lymphoblastic leukemia.