Breast cancer heterogeneity: parallel evolution or conscious uncoupling?

Breast cancer is known to display considerable inter- and intra-tumour genetic heterogeneity. It is now widely accepted that no two breast cancers harbour the same complement of genomic alterations, and that both primary and metastatic breast cancers are composed of multiple genetically diverse subclones that evolve under different selective pressures. Recent work published in the Journal of Pathology by Desmedt and colleagues questions the evolutionary dynamics of multi-focal breast cancer with similar pathological features by studying the mutational repertoire of different lesions. Whilst the majority of the lesions showed some common driver alterations, one-third lacked any common mutations, suggesting very early clonal divergence. These and other recent observations underscore the need for a fundamental understanding of the rules governing breast cancer evolution, and highlight the need for in-depth assessment of driver alterations for appropriate patient management and selective treatment.