Aneuploidy has long been associated with genetic instability and tumorigenesis. Dewhurst et al. examined the evolution and consequences of chromosomal aberrations using long-term culture of a diploid colon cancer progenitor cell line. Tetraploids — rare cells that survive genome doubling — have a greater tolerance for further chromosomal abnormalities. Furthermore, tetraploidy was associated with a low probability of disease-free survival.