The findings of a whole-genome sequencing study in patients with metastatic breast cancer provide further insight into the mechanisms of metastatic dissemination. Following analysis of 299 samples from 170 patients, researchers found that most metastases disseminate late in the evolution of the tumour, and, despite increasing diversity, contain many of the same driver mutations as the original tumour. However, investigators also noted the emergence of JAK–STAT pathway-inactivating mutations in metastases, but not in primary tumours, suggesting that this pathway is involved in disease progression.