CD19 and central nervous system leukemia: In the UCBT group, 10 (40.0%) patients relapsed at a median time of 6.2 months (range 1.4–22.3 months) including one CD19-negative relapse and one central nervous system leukemia (CNSL), and one patient underwent transformation from ALL to myelodysplastic syndrome (MDS) and eventually progressed to acute myeloid leukemia (AML).