Two studies analysed chromosomal abnormalities in buccal and blood cells from more than 100,000 individuals of different ages. Detectable abnormalities increased with age and were higher in patients with either solid or haematological cancers compared with cancer-free individuals (0.97% versus 0.74%). This indicates that genomic instability underlies both somatic cell mosaicism and cancer risk. Crucially, abnormalities in samples from undiagnosed individuals were predictive of future cancer diagnoses, so this approach may be a useful future screening tool.