 TEL/AML1 fusion gene is present in 20-25% of childhood acute lymphoblastic leukaemias.     ///    "In order to unravel at which stage of B-cell precursor development the fusion is originated, we analysed frequency and pattern of immunoreceptor (immunoglobulin and T-cell receptor) gene rearrangements in 47 TEL/AML1-positive and 43 TEL/AML1-negative cases of the same CD10+ immunophenotype. "    ///    More mature immunogenotype of TEL/AML1-positive cases and changes in 37% of rearrangements between diagnosis and relapse suggest that in most cases the TEL/AML1 fusion is formed during immunoreceptor gene rearrangement process..     ///    "Moreover, we compared corresponding immunoreceptor gene rearrangements in 11 cases of TEL/AML1-positive leukaemia at diagnosis and relapse. "    ///    TEL/AML1 and immunoreceptor gene rearrangements-which comes first?. 