Breast cancer cells, when disseminated to other secondary organs such as the lungs, may stay in a dormant state for years, even decades. But the mechanisms that limit their expansion are not well understood. This is what researchers call a dormant mesenchymal-like phenotype (M-like) before metastasis to the lungs. Now, scientists have shown in a study published Oct. 7, 2024, in Cell, that the limiting of disseminated breast cancer cells (DCCs) to metastasize in the lungs is due to alveolar macrophages (AMs), which activate signals that make DCCs stay dormant.