Fifty BCP-ALL samples at initial diagnosis and relapse, 26 adult and 24 pediatric patients, lacking cytogenetic rearrangements identified by conventional diagnostics (BCR-ABL1, KMT2A-AFF1, ETV6-RUNX1, TCF3-PBX1) were analysed as exploratory cohort (cohort 1, Additional file 4) [23]. This evidence concerns the gene PBX1 and acute lymphoblastic leukemia.