Breast cancer cells spread in an already-armed mob

Most tumor-driving mutations are carried from original malignancy, study suggests

cluster of tumor cells

ON THE ROAD  Breast cancer cells may break away from the main tumor in clumps, already bearing most of the mutations that will drive cancer recurrence, a study suggests. Shown here is a cluster of circulating tumor cells (red) from a patient with breast cancer.

Min Yu/USC Norris Comprehensive Cancer Center, NATIONAL CANCER INSTITUTE

COLD SPRING HARBOR, N.Y.