Fighting Breast Cancer (IMAGE) Michigan State University Caption In this microscope image, taken inside a living mouse, green tumor cells and red blood vessels are readily visible. But a closer look reveals small gray specks, which are monocytes and macrophages advancing on the tumor. Credit Bryan Smith 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.