The cytogenetic hallmark is the translocation t(12;22)(q13;q12) resulting in a chimeric EWS/ATF1 gene in which the 3'-terminal part of EWS at 22q is replaced by the 3'-terminal part of ATF1 at 12q.     ///    "The type 2 transcript of EWS/ATF1, an in-frame fusion of exon 7 of EWS with exon 5 of ATF1, was detected in 4 patients, as the only transcript in 1 case and together with other variants in 3 cases. "    ///    RT-PCR amplified EWS/ATF1 cDNA fragments in all patients and ATF1/EWS cDNA fragments in 6 of 10 patients.     ///    "Sequencing of the amplified ATF1/EWS cDNA fragments showed in 5 patients that ATF1 exon 3 was fused with EWS exon 10, resulting in an out-of-frame chimeric transcript. "    ///    "As an initial step in the characterization of the EWS/ATF1 and ATF1/EWS chimeras, we constructed an exon/intron map of the ATF1 gene. "