Molecular tumour clocks and colorectal cancer: seeing the unseen

Recent advances in mathematics and sequencing have revolutionised the analysis of evolution. Modern phylogeny is molecular phylogeny, or histories reconstructed from sequences. The same quantitative sequence approaches have not been fully translated to colorectal cancer. Molecular tumour clocks provide opportunities to reconstruct individual tumour histories. Phenotypic and genetic progression are usually thought to be synonymous, but many mutations may accumulate in normal appearing cells. Although such occult genetic progression is essentially invisible, molecular tumour clocks offer the somewhat magical ability to reconstruct what may never be seen. Potentially much of colorectal cancer progression is unseen and unexplored because tumours usually appear late in life.