Ethidium bromide–stained gel showing expression of RUNX1-PRDM16 fusion transcript (upper RT-PCR product of 272 bp, confirmed by sequencing analysis) for 3 of 7 analyzed patients (UPNs 9, 11, and 17). Sequencing data after purification of the lower band revealed unspecific RT-PCR products (UPN 11 and UPN 13). The EF1α RT-PCR product (221 bp) was used as the endogenous control.