Given the abundance of intratumor macrophages in multiple solid cancers (8), including breast cancer, the pro-tumorigenic effects of macrophage-derived Wnt7b secretion in breast cancer (27), and a recent study of decreased primary lung tumor growth following β-catenin knockout in total F4/80+ macrophages (29), we tested the hypothesis that heightened β-catenin signaling in macrophages, particularly TRMs of the lung, enhanced metastatic outcome. The gene discussed is WNT7B; the disease is breast cancer.