The genetic events that cause colorectal adenomas to progress to carcinomas remain largely undetermined. Using multi-region genome/exome sequencing of 24 benign and malignant colorectal tumours, we probe the evolutionary fitness landscape occupied by these neoplasms. Unlike carcinomas, advanced adenomas frequently harbour sub-clonal driver mutations, hence lack selective sweeps, and have relatively high genetic heterogeneity. Carcinomas are distinguished from adenomas not by nucleotide-level mutations (drivers or burden), but by widespread aneusomies that are usually clonal and often accrue in a “punctuated” fashion. Adenomas evolve across an undulating fitness landscape, whereas carcinomas occupy a sharper fitness peak, probably owing to stabilising selection.

The genetic events that cause colorectal adenomas to progress to carcinomas remain largely undetermined. Using multi-region genome/exome sequencing of 24 benign and malignant colorectal tumours, we probe the evolutionary fitness landscape occupied by these neoplasms. Unlike carcinomas, advanced adenomas frequently harbour sub-clonal driver mutations, hence lack selective sweeps, and have relatively high genetic heterogeneity. Carcinomas are distinguished from adenomas not by nucleotide-level mutations (drivers or burden), but by widespread aneusomies that are usually clonal and often accrue in a “punctuated” fashion. Adenomas evolve across an undulating fitness landscape, whereas carcinomas occupy a sharper fitness peak, probably owing to stabilising selection.

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