However, due to different translocation partner genes at chromosomes 1 and 19, distinct subtypes of hyperdiploid B-ALL with t(1;19)/der(19)t(1;19) are recognized based on the presence or absence of the TCF3-PBX1 fusion gene, but the cytogenetic and etiologic differences between the two remain understudied.     ///    "Fluorescence in situ hybridization (FISH) on previously G-banded metaphases using the LSI TCF3/PBX1 Dual Color, Dual Fusion Translocation Probe confirmed the presence of the TCF3-PBX1 gene fusion. "    ///    Such molecular studies may provide insight into the precise differences between TCF3-PBX1 positive and negative hyperdiploid B-ALL bearing the t(1;19)(q23;p13)..     ///    "The t(1;19)(q23;p13), which can result in the TCF3-PBX1 chimeric gene, is one of the most frequent translocations in B-acute lymphoblastic leukemia (B-ALL) and is observed in both adult and pediatric populations at an overall frequency of 6%."    ///    " The t(1;19)(q23;p13), which can result in the TCF3-PBX1 chimeric gene, is one of the most frequent translocations in B-acute lymphoblastic leukemia (B-ALL) and is observed in both adult and pediatric populations at an overall frequency of 6%. "    ///    "This case is one of only a few cases with both hyperdiploidy and a confirmed TCF3-PBX1 fusion, demonstrating the importance of using FISH for proper molecular classification of these cases in order to distinguish them from those with hyperdiploidy but no TCF3-PBX1 fusion gene. "    ///    A (1;19) translocation involving TCF3-PBX1 fusion within the context of a hyperdiploid karyotype in adult B-ALL: a case report and review of the literature..     ///    This particular pattern with a TCF3-PBX1 fusion within the context of a hyperdiploid karyotype is seen in B-ALL and is usually associated with a poor outcome. 