Proximity Ligation Assay is a reliable tool for the detection of ETV6-RUNX1 fusion protein in patients’ lymphoblasts. Quantification of PLA signals per nucleus in lymphoblasts from two patients negative (a) or positive (b) for the fusion protein ETV6-RUNX1. The cells were incubated with RUNX1 ab110035 antibodies alone (−) or with RUNX1 ab23980, CBFB ab133600 or ETV6 sc11382 antibodies. The quantification of the number of PLA dot per nucleus is presented with the mean values ± S.D. The line represents the cut-off used to determine positive PLA signals