Macrophage (IMAGE) University of California - San Diego Caption Macrophages play key roles in the tumor microenvironment. In this microscope image from a live mouse, tumor cells (labeled in green) are surrounded by tumor macrophages (labeled in red). Credit Ralph Weissleder, MD, PhD, National Cancer Institute Usage Restrictions Credit as indicated 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.