Breast cancer tumor, NCI (IMAGE) University of California - San Diego Caption In this image of a human breast tumor, a cluster of malignant cells that have become resistant to chemotherapy are shown in red. Credit <p>Image courtesy of <a href="https://visualsonline.cancer.gov/details.cfm?imageid=10574" target="_blank">NCI</a></p> Usage Restrictions Use photo credit 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.