Chronic stress promotes adrenergic-dependent infiltration of macrophages into primary mammary tumors, leading to enhanced metastasis. In an immunofluorescence analysis, anti–β2-adrenergic receptor (green), anti-F4/80 (red), and nuclear counterstaining (blue) were used to visualize 66cl4 mammary tumor cryosections from control and stressed mice. For details, see the article by Sloan and colleagues on page 7042 of this issue.