Leader Cells in a Mouse Breast Tumor (IMAGE) Johns Hopkins Medicine Caption A breast tumor (blue) uses leader cells (green) to invade muscle tissue (red) in a mouse. Credit Kevin Cheung, courtesy of <i>Cell</i> Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.