Prenatal Origin of TEL-AML1--Positive Acute

EL-AML1 in Europe by demonstrating its occurrence in a California-born population. Secondary changes were also similar to those described previously, with deletion of the second TEL allele being the most common. Other secondary changes included duplication of the fusion gene, trisomy 21, and monosomy X. 2003 Wiley-Liss, Inc. INTRODUCTION As with other types of cancer, leukemia is a heterogeneous disease whereby nonrandom genetic aberrations, such as chromosomal translocations, are complemented by secondary genetic aberrations that give rise to leukemic clones. In infant leukemia and common acute lymphoblastic leukemia (cALL) of early childhood, all of the molecular changes necessary to generate disease occur within a relatively narrow time frame, affording an opportunity for investigation of the etiology of such leukemias. Compelling evidence has demonstrated that chromosomal translocations are early events in leukemogenesis, occurring in utero. Initially, studies in twins with co