This study confirmed that TEL/AML1 gene fusion is the most common genetic event in pediatric ALL in Japan and is restricted to CD10-positive B-precursor ALL.     ///     A retrospective study was conducted to investigate the prognostic significance of TEL/AML1 fusion resulting from a cryptic t(12;21) in Japanese patients with childhood B-precursor acute lymphoblastic leukemia (ALL).     ///    "Although the overall 5-year survival rate was better among patients with TEL/AML1 fusion transcript than among those without it (87.3 +/- 8.7% versus 75.9 +/- 5.8%, respectively), the 5-year disease-free survival (DFS) rates of patients with TEL/AML1 fusion transcript and those without it were similar (64.0 +/- 13.5% versus 69.1 +/- 6.3%, respectively). "    ///    Prognostic significance of TEL/AML1 fusion transcript in childhood B-precursor acute lymphoblastic leukemia..     ///    "However, for 57 patients treated with the latest intensive protocol, the 4-year DFS rate was much higher for the patients with TEL/AML1 fusion transcript than for those without it (100.0% v.s. "    ///    "TEL/AML1 was not found in any samples from the patients with T-ALL, B-ALL, or CD10-negative B-precursor ALL. "    ///    "Therefore, these data suggest that the patients with TEL/AML1 may not necessarily be candidates for less aggressive treatment.. "    ///    The frequency of patients with TEL/AML1 was 16% (23 of 144) and all patients with TEL/AML1 also had CD10-positive B-precursor ALL.     ///    "Among patients with CD10-positive B-precursor ALL, age, initial white blood cell count, and immunophenotype did not differ with TEL/AML1 positivity, although the patients were predominantly male (p < 0.01). "    ///    Five of the 21 (23.8%) patients with TEL/AML1 relapsed and 4 of these relapsed > 24 months after diagnosis. 