• minimal residual disease;
  • pediatric acute lymphoblastic leukemia;
  • real-time quantitative PCR;
  • scanning fluorescence microscopy;
  • t(12;21) rearrangement


DNA-, RNA-, and cell-based methods provide different biologic information for determining the presence of minimal residual disease (MRD). We monitored the responses of patients with pediatric acute lymphoblastic leukemia (pALL) using DNA markers, TEL/AML1 expression, and scanning fluorescence microscopy (SFM). Using SFM, 36% of patients exhibited 1.5–3.1 log and 2.9–4.2 log higher MRD levels compared with those based on DNA and RNA markers, respectively. CD10+ ancestor cells with germline antigen receptors, but silent TEL/AML1 expression, may reside in the lymphoid stem cell compartment of treated t(12;21)-positive patients and might act as a potential source of cells for late relapses. Pediatr Blood Cancer 2010; 54:158–160. © 2009 Wiley-Liss, Inc.