While the molecular subtype is likely not the only factor that influences premetastatic changes to the stromal and soluble lung microenvironment in breast cancer, the differential results between TN and luminal A models seen in this study set the stage for future studies aimed at elucidating this concept further through investigation of other clinically used molecular subtypes (HER2+ and luminal B), as well as subsets of the triple-negative subtype. Here, ERBB2 is linked to breast cancer.