Between 1998 and 2002, we analyzed the cord blood of 253 healthy newborns for the presence of TEL/AML1 (n=253), MLL/AF4 (n=103), and BCR/ABL (n=103) fusion transcripts using standard end-point reverse transcription–polymerase chain reaction (RT-PCR; 197 samples) or quantitative RT-PCR (TEL/ AML1 only; 56 samples). While all tested samples proved to be BCR/ABL and MLL/AF4 negative we found that of the cord blood tested, 5 of 253 (2%) bore the TEL/AML1 fusion.
Moreover, we tested tissues taken from aborted fetuses (1 x spleen, 11 x liver) for the presence of TEL/AML1 and we found the spleen tissue positive (abortion for sepsis in 29th week of gestation). We have several reasons to consider the positively tested samples genuinely positive rather than contaminated.