Even though they may be an in vitro artifact resulting from repeated passaging, it is interesting that in KU812 the acrocentric chromosome marker that harbours tandem duplications of BCR/ABL1 fusion and a 1 Mb long 9q34 amplicon is similar to the chromosome markers that some CML patients acquire in vivo, suggesting the possibility that this subclone had already been present in the original sample when the cell line was established and had expanded under in vitro cell culture conditions thanks to a proliferative advantage. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.