This unique case study demonstrates that ETV6/AML1 fusion and the associated complex chromosomal rearrangements occurred in utero.     ///    "Identical twin girls, aged 4 years, developed ETV6/AML1-positive acute lymphoblastic leukaemia (ALL) within 3 months of one another. "    ///    "This is the first report of a complex cytogenetic clone, in association with an ETV6/AML1 fusion, developing in utero. "