Next-generation sequencing (NGS) showed STAG2 gene mutations in the bone marrow, and reverse transcription-polymerase chain reaction (RT–PCR) showed that common fusion genes for BCP-ALL, including TCF3-PBX1, TCF3-HLF, ETV6-RUNX1 and BCR-ABL, were negative. Here, TCF3 is linked to acute lymphoblastic leukemia.