To investigate the frequency of the molecular equivalent of the t(12;21), the TEL/AML1 gene fusion, we have undertaken a prospective screening in the running German Berlin-Frankfurt-M?nster (BFM) and Italian Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP) multicenter ALL therapy trials.     ///    Incidence and clinical relevance of TEL/AML1 fusion genes in children with acute lymphoblastic leukemia enrolled in the German and Italian multicenter therapy trials.     ///    A total of 342 children were investigated for the presence of TEL/AML1 fusion gene and 99 cases (28.9%) were positive.     ///    "Whereas three of the TEL/AML1 positive cases (3.0%) have relapsed to date, 27 patients without TEL/AML1 rearrangement (11.1%) suffered from relapse. "    ///    "Based on this prospective analysis, we retrospectively evaluated the impact of TEL/AML1 in prognosis by identifying the subset of B-lineage ALL children enrolled in the closed German ALL-BFM-90 and Italian ALL-AIEOP-91 protocols who had sufficient material for analysis. "    ///    DNA index was available for 59 of the 63 TEL/AML1 positive cases.     ///    "The 63 cases positive for the TEL/AML1 chimeric products ranged in age between 1 and 12 years, and all but one showed CD10 and pre-B immunophenotype. "    ///    The patients expressing the TEL/AML1 fusion mRNA appeared to have a better event-free survival (EFS) than the patients who lacked this chimeric product. 